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Resident macrophages orchestrate homeostatic, inflammatory, and reparative activities. It is appreciated that different tissues instruct specialized macrophage functions. However, individual tissues contain heterogeneous subpopulations, and how these subpopulations are related is unclear. We asked whether common transcriptional and functional elements could reveal an underlying framework across tissues. Using single-cell RNA sequencing and random forest modeling, we observed that four genes could predict three macrophage subsets that were present in murine heart, liver, lung, kidney, and brain. Parabiotic and genetic fate mapping studies revealed that these core markers predicted three unique life cycles across 17 tissues. TLF + (expressing TIMD4 and/or LYVE1 and/or FOLR2) macrophages were maintained through self-renewal with minimal monocyte input; CCR2 + (TIMD4 − LYVE1 − FOLR2 − ) macrophages were almost entirely replaced by monocytes, and MHC-II hi macrophages (TIMD4 − LYVE1 − FOLR2 − CCR2 − ), while receiving modest monocyte contribution, were not continually replaced. Rather, monocyte-derived macrophages contributed to the resident macrophage population until they reached a defined upper limit after which they did not outcompete pre-existing resident macrophages. Developmentally, TLF + macrophages were first to emerge in the yolk sac and early fetal organs. Fate mapping studies in the mouse and human single-cell RNA sequencing indicated that TLF + macrophages originated from both yolk sac and fetal monocyte precursors. Furthermore, TLF + macrophages were the most transcriptionally conserved subset across mouse tissues and between mice and humans, despite organ- and species-specific transcriptional differences. Here, we define the existence of three murine macrophage subpopulations based on common life cycle properties and core gene signatures and provide a common starting point to understand tissue macrophage heterogeneity.

Dendritic cells (DCs) are the most specialized APCs that play a critical role in driving Th2 differentiation, but the mechanism is not fully understood. Here we show that vacuolar protein sorting 33B (Vps33B) plays an important role in this process. Mice with Vps33b -specific deletion in DCs, but not in macrophages or T cells, were more susceptible to Th2-mediated allergic lung inflammation than wild-type mice. Deletion of Vps33B in DCs led to enhanced CD4 + T cell proliferation and Th2 differentiation. Moreover, Vps33B specifically restrained reactive oxygen species production in conventional DC1s to inhibit Th2 responses in vitro, whereas Vps33B in monocyte-derived DCs and conventional DC2s was dispensable for Th2 development in asthma pathogenesis. Taken together, our results identify Vps33B as an important molecule that mediates the cross-talk between DCs and CD4 + T cells to further regulate allergic asthma pathogenesis., (Copyright © 2021 by The American Association of Immunologists, Inc.)

The loss of function of exocyst subunit EXO70B1 leads to autoimmunity, which is dependent on TIR-NBS2 (TN2), a truncated intracellular nucleotide-binding and leucine-rich repeat receptor (NLR). However, how TN2 triggers plant immunity and whether typical NLRs are required in TN2-activated resistance remain unclear. Through the CRISPR/Cas9 gene editing system and knockout analysis, we found that the spontaneous cell death and enhanced resistance in exo70B1-3 were independent of the full-length NLR SOC3 and its closest homolog SOC3-LIKE 1 (SOC3-L1). Additionally, knocking out SOC3-L1 or TN2 did not suppress the chilling sensitivity conferred by chilling sensitive 1-2 (chs1-2). The ACTIVATED DISEASE RESISTANCE 1 (ADR1) family and the N REQUIREMENT GENE 1 (NRG1) family have evolved as helper NLRs for many typical NLRs. Through CRISPR/Cas9 gene editing methods, we discovered that the autoimmunity of exo70B1-3 fully relied on ADR1s, but not NRG1s, and ADR1s contributed to the upregulation of TN2 transcript levels in exo70B1-3. Furthermore, overexpression of TN2 also led to ADR1-dependent autoimmune responses. Taken together, our genetic analysis highlights that the truncated TNL protein TN2-triggered immune responses require ADR1s as helper NLRs to activate downstream signaling, revealing the importance and complexity of ADR1s in plant immunity regulation., (© 2021 Society for Experimental Biology and John Wiley & Sons Ltd.)

Tumor cells evade T cell-mediated immunosurveillance via the interaction between programmed death-1 (PD-1) ligand 1 (PD-L1) on tumor cells and PD-1 on T cells. Strategies disrupting PD-1/PD-L1 have shown clinical benefits in various cancers. However, the limited response rate prompts us to investigate the molecular regulation of PD-L1. Here, we identify trafficking protein particle complex subunit 4 (TRAPPC4), a major player in vesicular trafficking, as a crucial PD-L1 regulator. TRAPPC4 interacts with PD-L1 in recycling endosomes, acting as a scaffold between PD-L1 and RAB11, and promoting RAB11-mediated recycling of PD-L1, thus replenishing its distribution on the tumor cell surface. TRAPPC4 depletion leads to a significant reduction of PD-L1 expression in vivo and in vitro. This reduction in PD-L1 facilitates T cell-mediated cytotoxicity. Overexpression of Trappc4 sensitizes tumor cells to checkpoint therapy in murine tumor models, suggesting TRAPPC4 as a therapeutic target to enhance anti-tumor immunity., (© 2021. The Author(s).)

Hepatocytes compose up to 80% of the total liver and have been indicated as important players in the induction of immunologic tolerance in this organ. We show that hepatocytes possess the molecular machinery required for the cross-presentation of extracellular antigens. Using a derivative of the model antigen ovalbumin (OVA) covalently modified with a polymer containing multiple N-acetylgalactosamine residues (pGal-OVA) that enhance extracellular antigen uptake by mimicking the glycome of apoptotic debris, we show efficient hepatocyte-dependent induction of cross-tolerance of both adoptively transferred OT-I cells and endogenous OVA-specific CD8 + T lymphocytes, for example inducing tolerance to OVA-expressing skin transplants. Our study confirms that hepatocytes are capable of inducing peripheral tolerogenesis and provides proof of concept that they may be a valuable candidate for in vivo targeted tolerogenic treatments., Competing Interests: The EPFL has filed for patent protection on the pGal-antigen delivery platform, and MD, DW, and JH are named as inventors on those patents. Anokion SA and Kanyos Bio, Inc., have licensed those patents, and JH and DW participate in equity in those companies. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Damo, Wilson, Watkins and Hubbell.)

Brain metastases (BM) are an ever-increasing challenge in oncology, threatening quality of life and survival of many cancer patients. The majority of BM originate from lung adenocarcinoma, and stage III patients have a risk of 40-50% to develop BM in the first years of disease onset. As therapeutic options are limited, prevention of their occurrence is an attractive concept. Here we investigated whether Nintedanib (BIBF 1120), a tyrosine kinase inhibitor (TKI) targeting the VEGF pathway approved for lung adenocarcinoma, and the dual anti-VEGF-A/Ang2 nanobody BI836880 have the potential to prevent BM formation. A mouse model of brain metastasis from lung adenocarcinoma was used in which tumor cells were injected intracardially. Metastases formation occurred inside and outside of the brain and was followed by MRI, IVIS, and immunohistochemistry. BM were reduced in volume and number by both Nintedanib and the dual anti-VEGF-A/Ang2 nanobody, which translated into improved survival. Both compounds were able to normalize cerebral blood vessels at the site of brain metastatic lesions. Extracranial metastases, however, were not reduced, and meningeal metastases only partially. Interestingly, unspecific control IgG also lead to brain vessel normalization and reduction of brain and meningeal metastases. This data indicates a brain-specific group effect of antiangiogenic compounds with respect to metastasis prevention, most likely by preventing an early angiogenic switch. Thus, Nintedanib and BI836880 are promising candidates for future BM preventive study concepts in lung adenocarcinoma patients.

Aims: Epstein-Barr virus (EBV) targets predominantly B cells and these cells could acquire new phenotype characteristics. Here we analyzed whether EBV-infected and -uninfected B cells from healthy subjects differ in proportion of dominant phenotypes, maturation stage, and homing receptors expression., Methods: EBV-infected and -uninfected cells were identified by flow cytometry using fluorophore-labeled EBV RNA-specific DNA probes combined with fluorophore-labeled antibody to surface lineage markers, integrins, chemokine receptors, and immunoglobulin isotypes, including intracellular ones., Results: Our results show that the trafficking characteristics of EBER pos B cells are distinct from EBER neg B cells with most dominant differences detected for α4β1 and α4β7 and CCR5 and CCR7. EBV-positive cells are predominantly memory IgM + B cells or plasmablasts/plasma cells (PB/PC) positive for IgA or less for IgM. In comparison to uninfected B cells, less EBV-positive B cells express α4β7 and almost no cells express α4β1. EBV-positive B cells contained significantly higher proportion of CCR5 + and CCR7 + cells in comparison to EBV-negative cells. In vitro exposure of blood mononuclear cells to pro-inflammatory cytokine IL-6 reduces population of EBV-positive B cell., Conclusion: Although EBV-infected B cells represent only a minor subpopulation, their atypical functions could contribute in predisposed person to development abnormities such as some autoimmune diseases or tumors. Using multi-parameter flow cytometry we characterized differences in migration of EBV-positive and -negative B cells of various maturation stage and isotype of produced antibodies particularly different targeting to mucosal tissues of gastrointestinal and respiratory tracts.

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease affecting the joints and surrounding tissue. Identification of novel proteins associated with the progression of a disease is a prerequisite for understanding the pathogenesis of RA. The present study was undertaken to identify the potential biomarkers from a less explored biological sample such as synovial fluid (SF) cells which is specific for RA and to analyze their functional aspects using proteomic approach. Two-dimensional gel electrophoresis (2-DE) was performed using synovial fluid cells of RA and osteoarthritis (OA) patients, and 7 differentially expressed proteins were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS/MS). Αlpha-Taxilin ( α -Taxilin) has been found as one of the novel, significantly up regulated protein in RA. It has been validated in the synovium, synovial fluid (SF), SF cells, and plasma samples by Western blot, enzyme-linked immunosorbent assay (ELISA), fluorescence-activated cell sorting (FACS), immunohistochemistry (IHC), and real-time PCR. The identification of autoantibody against α -Taxilin and in silico studies has further helped us to understand its involvement in disease mechanism. The present study will therefore provide knowledge towards the etiology of RA that pave the way for suitable prognostic marker identification along with other clinical parameters., Competing Interests: The authors confirm that this article content has no conflicts of interest., (Copyright © 2020 Ashish Sarkar et al.)

Yellow head disease (YHD) is an infectious disease of Penaeus monodon which is caused by the yellow head virus (YHV). YHV infection invariably leads to 100% shrimp mortality within 3-5 days. Currently, an effective method to prevent or cure shrimp from YHV infection has not been elucidated. Therefore, the molecular mechanism underlying YHV infection should be examined. In this study, early endosome antigen 1 (EEA1) protein that was involved in the tethering step of the vesicle and early endosome fusion was investigated during YHV infection. The open reading frame of P. monodon EEA1 (PmEEA1) was cloned and sequenced (3000 bp). It encoded a putative protein of 999 amino acids and contained the zinc finger C 2 H 2 domain signature at the N-terminus and the FYVE domain at the C-terminus. Suppression of PmEEA1 by specific dsRNA in shrimp showed inhibition of YHV replication after 48 h post YHV injection (hpi). On the other hand, shrimp received only NaCl without any dsRNA showed high YHV levels at approximately one hundred thousand times at 24 hpi and 48 hpi. Moreover, silencing of PmEEA1 by specific dsRNA followed by YHV challenge demonstrated a delay in shrimp mortality from 60 hpi to 168 hpi when compared to the control. These results indicated that YHV required PmEEA1 for trafficking within the infected cells, strongly suggesting that PmEEA1 may be a potential target to control and prevent YHV infection in P. monodon., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

STING plays central roles in the innate immune response to pathogens that contain DNA. Sensing cytoplasmic DNA by cyclic GMP-AMP synthase produces cyclic GMP-AMP, which binds to and activates STING and induces STING translocation from the endoplasmic reticulum to the perinuclear microsome. However, this trafficking process has not been fully elucidated yet. In this study, we identified YIPF5 as a positive regulator of STING trafficking. YIPF5 is essential for DNA virus- or intracellular DNA-triggered production of type I IFNs. Consistently, knockdown of YIPF5 impairs cellular antiviral responses to DNA virus. Mechanistically, YIPF5 interacts with both STING and components of COPII, facilitating STING recruitment to COPII in the presence of cytoplasmic dsDNA. Furthermore, knockdown of components of COPII inhibits DNA virus-triggered production of type I IFNs, suggesting that COPII is involved in innate immune responses to DNA viruses. Collectively, our findings demonstrate that YIPF5 positively regulates STING-mediated innate immune responses by recruiting STING to COPII-coated vesicles and facilitating STING trafficking from the endoplasmic reticulum to Golgi, providing important insights into the molecular mechanisms of intracellular DNA-stimulated STING trafficking and activation., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Canine distemper virus (CDV) causes a fatal demyelinating leukoencephalitis in young dogs resembling human multiple sclerosis. Astrocytes are the main cellular target of CDV and undergo reactive changes already in pre-demyelinating brain lesions. Based on their broad range of beneficial and detrimental effects in the injured brain reactive astrogliosis is in need of intensive investigation. The aim of the study was to characterize astrocyte plasticity during the course of CDV-induced demyelinating leukoencephalitis by the aid of immunohistochemistry, immunofluorescence and gene expression analysis. Immunohistochemistry revealed the presence of reactive glial fibrillary acidic protein (GFAP) + astrocytes with increased survivin and reduced aquaporin 4, and glutamine synthetase protein levels, indicating disturbed blood brain barrier function, glutamate homeostasis and astrocyte maladaptation, respectively. Gene expression analysis revealed 81 differentially expressed astrocyte-related genes with a dominance of genes associated with neurotoxic A1-polarized astrocytes. Accordingly, acyl-coA synthetase long-chain family member 5 + /GFAP + , and serglycin + /GFAP + cells, characteristic of A1-astrocytes, were found in demyelinating lesions by immunofluorescence. In addition, gene expression revealed a dysregulation of astrocytic function including disturbed glutamate homeostasis and altered immune function. Observed findings indicate an astrocyte polarization towards a neurotoxic phenotype likely contributing to lesion initiation and progression in canine distemper leukoencephalitis.

Neutrophil chemotaxis is essential in responses to infection and underlies inflammation. In neutrophils, the small GTPase Rac1 has discrete functions at both the leading edge and in the retraction of the trailing structure at the cell's rear (uropod), but how Rac1 is regulated at the uropod is unknown. Here, we identified a mechanism mediated by the trafficking protein synaptotagmin-like 1 (SYTL1 or JFC1) that controls Rac1-GTP recycling from the uropod and promotes directional migration of neutrophils. JFC1-null neutrophils displayed defective polarization and impaired directional migration to N-formyl-methionine-leucyl-phenylalanine in vitro, but chemoattractant-induced actin remodeling, calcium signaling and Erk activation were normal in these cells. Defective chemotaxis was not explained by impaired azurophilic granule exocytosis associated with JFC1 deficiency. Mechanistically, we show that active Rac1 localizes at dynamic vesicles where endogenous JFC1 colocalizes with Rac1-GTP. Super-resolution microscopy (STORM) analysis shows adjacent distribution of JFC1 and Rac1-GTP, which increases upon activation. JFC1 interacts with Rac1-GTP in a Rab27a-independent manner to regulate Rac1-GTP trafficking. JFC1-null cells exhibited Rac1-GTP accumulation at the uropod and increased tail length, and Rac1-GTP uropod accumulation was recapitulated by inhibition of ROCK or by interference with microtubule remodeling. In vivo, neutrophil dynamic studies in mixed bone marrow chimeric mice show that JFC1 -/- neutrophils are unable to move directionally toward the source of the chemoattractant, supporting the notion that JFC1 deficiency results in defective neutrophil migration. Our results suggest that defective Rac1-GTP recycling from the uropod affects directionality and highlight JFC1-mediated Rac1 trafficking as a potential target to regulate chemotaxis in inflammation and immunity., (©2019 Society for Leukocyte Biology.)

NOD2 and TLR2 recognize components of bacterial cell wall peptidoglycan and direct defense against enteric pathogens. CD8 + T cells are important for immunity to such pathogens but how NOD2 and TLR2 induce antigen specific CD8 + T cell responses is unknown. Here, we define how these pattern recognition receptors (PRRs) signal in primary dendritic cells (DCs) to influence MHC class I antigen presentation. We show NOD2 and TLR2 phosphorylate PI31 via TBK1 following activation in DCs. PI31 interacts with TBK1 and Sec16A at endoplasmic reticulum exit sites (ERES), which positively regulates MHC class I peptide loading and immunoproteasome stability. Following NOD2 and TLR2 stimulation, depletion of PI31 or inhibition of TBK1 activity in vivo impairs DC cross-presentation and CD8 + T cell activation. DCs from Crohn's patients expressing NOD2 polymorphisms show dysregulated cross-presentation and CD8 + T cell responses. Our findings reveal unidentified mechanisms that underlie CD8 + T cell responses to bacteria in health and in Crohn's.

The lymphatics fulfill a vital physiological function as the conduits through which leucocytes traffic between the tissues and draining lymph nodes for the initiation and modulation of immune responses. However, until recently many of the molecular mechanisms controlling such migration have been unclear. As a result of careful research, it is now apparent that the process is regulated at multiple stages from initial leucocyte entry and intraluminal crawling in peripheral tissue lymphatics, through to leucocyte exit in draining lymph nodes where the migrating cells either participate in immune responses or return to the circulation via efferent lymph. Furthermore, it is increasingly evident that most if not all leucocyte populations migrate in lymph and that such migration is not only important for immune modulation, but also for the timely repair and resolution of tissue inflammation. In this article, I review the latest research findings in these areas, arising from new insights into the distinctive ultrastructure of lymphatic capillaries and lymph node sinuses. Accordingly, I highlight the emerging importance of the leucocyte glycocalyx and its novel interactions with the endothelial receptor LYVE-1, the intricacies of endothelial chemokine secretion and sequestration that direct leucocyte trafficking and the significance of the process for normal immune function and pathology.

Most endosomal sorting complex required for transport (ESCRT)-III proteins are not fully functional when expressed as fusion of fluorescent or epitope tags, frequently making the use of specific antibodies the only available method for their detection. Heterologous expression of ESCRT-III proteins in bacteria often results in the formation of insoluble aggregates or inclusion bodies that interfere with their purification. However, inclusion bodies are usually pure protein aggregates with high antigenicity. In addition, since proteins within inclusion bodies are presented in a range of folding states, immunization with inclusion bodies can potentially result in antibodies with specificity for different folding states of the protein under study. We describe here a protocol to isolate bacterial inclusion bodies of plant ESCRT-III proteins for production of polyclonal antibodies. We also describe a nitrocellulose-based immunoaffinity purification method that allows the immobilization of ESCRT-III proteins and the subsequent isolation of specific antibodies from a crude serum.

Tool Like Receptors (TLR) are transmembrane proteins that play an important role in immune reactions associated with the recognition of pathogenic factors that cause infection. However, chronic inflammatory conditions associated with the activation of these receptors create favorable conditions for the development of cancerous processes. The relationship between nuclear PPARγ receptors and TLR receptors is also important, whose role and importance in the process of carcinogenesis is the subject of various studies.

Autophagy-related 10 (ATG10) is essential for autophagy since it promotes ATG5-ATG12 complex formation. Our previous study found that there are two isoforms of the ATG10 protein, ATG10 (a longer one) and ATG10S, which have identical sequences except an absence of a 36-amino acid fragment (peptide B) in ATG10S, yet exhibit distinct effects on HCV genome replication. Here, we report the existence of two amino acids, cysteine at residue 44 and 135 (Cys 44 and Cys 135 , respectively), in ATG10 being related to differential effects of ATG10 on HCV replication and autophagy flux. Through a series of ATG10 mutation experiments and protein modeling prediction, we found that Cys 44 was involved in the dual role of the two isoforms of ATG10 protein on HCV replication and autophagy flux, and that Cys 135 plays similar roles as Cys 44 , but the disulfide bond of Cys 44 -Cys 135 was not verified in the ATG10 protein. Further analyses by full HCV virion infection confirmed the roles of -SH of Cys 44 and Cys 135 on HCV replication. ATG10 with deleted or mutated Cys 44 and/or Cys 135 could activate expression of innate immunity-related genes, including il28a, irf-3, irf-7 , and promote complete autophagy by driving autophagosomes to interact with lysosomes via IL28A-mediation. Subcellular localization assay and chromatin immunoprecipitation assay showed that ATG10 with the sulfydryl deletion or substitution of Cys 44 and Cys 135 could translocate into the nucleus and bind to promoter of IL28A gene; the results indicated that ATG10 with Cys 44 and/or Cys 135 absence might act as transcriptional factors to trigger the expression of anti-HCV immunological genes, too. In conclusion, our findings provide important information for understanding the differential roles on HCV replication and autophagy flux between ATG10 and ATG10S, and how the structure-function relationship of ATG10 transformed by a single -SH group loss on Cys 44 and Cys 135 in ATG10 protein, which may be a new target against HCV replication.

Problem: The lymphatic vasculature controls leukocytes trafficking and limits the adaptive immune response. In previous models of preeclampsia (PE), defective immune function caused by disruption of lymphangiogenesis was shown to be involved in the disease pathophysiology. Especially, the dysfunction of regulatory T cells (Treg) at the maternal-fetal interface may be one of the causes of severe PE. In particular, activation of Tregs to obtain immune tolerance requires adequate antigen presentation through the lymphatic system. We hypothesized that impaired lymphangiogenesis and imbalanced Tregs at the maternal-fetal interface are associated with the pathophysiology of severe PE. However, the current research addressing this hypothesis is limited. Therefore, to compare differences in lymphangiogenesis in severe PE and normal conditions, we aimed to examine the location of lymphatics at the maternal-fetal interface and to investigate the association between lymphangiogenesis and Tregs in severe PE., Method of Study: We obtained entire uterus from normal pregnant mice. Placental and fetal membranes, including decidua, were obtained from 10 pregnant women with severe PE and 10 gestational age-matched controls. Immunohistochemistry for LYVE1 was used to localize the distribution of lymphatic vessels and CD4, CD25, and FOXP3 for Treg., Results: LYVE1-positive vessels were present in the uterine wall of mice. LYVE1-positive lymphatic vessels were localized on the human decidua. Tubular lymphatics were abundant in the control decidua, but significantly reduced in severe PE. Furthermore, lymphatic vessel density correlated with the number of decidual Tregs., Conclusion: Abnormal decidual lymphangiogenesis is associated with reduced numbers of decidual Tregs in severe PE., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Retromer complex plays a crucial role in intracellular protein trafficking and is conserved throughout the eukaryotes including malaria parasite, Plasmodium falciparum, where it is partially conserved. The assembly of retromer complex in RBC stages of malarial parasite is extremely difficult to explore because of its complicated physiology, small size, and intra-erythrocytic location. Nonetheless, understanding of retromer assembly may pave new ways for the development of novel antimalarials targeting parasite-specific protein trafficking pathways. Here, we investigated the assembly of retromer complex in P. falciparum, by an immunosensing method through highly sensitive Surface Plasmon Resonance (SPR) technique. After taking leads from the bioinformatics search and literature, different interacting proteins were identified and specific antibodies were raised against them. The sensor chip was prepared by covalently linking antibody specific to one component and the whole cell lysate was passed through it in order to trap the interacting complex. Antibodies raised against other interacting components were used to detect them in the trapped complex on the SPR chip. We were able to detect three different components in the retromer complex trapped by the immobilized antibody specific against a different component on a sensor chip. The assay was reproduced and validated in a different two-component CD74-MIF system in mammalian cells. We, thus, illustrate the assembly of retromer complex in P. falciparum through a bio-sensing approach that combines SPR with immunosensing requiring a very small amount of sample from the native source., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Immunotherapy has emerged as a major therapeutic modality in oncology. Currently, however, the majority of patients with cancer do not derive benefit from these treatments. Vascular abnormalities are a hallmark of most solid tumours and facilitate immune evasion. These abnormalities stem from elevated levels of proangiogenic factors, such as VEGF and angiopoietin 2 (ANG2); judicious use of drugs targeting these molecules can improve therapeutic responsiveness, partially owing to normalization of the abnormal tumour vasculature that can, in turn, increase the infiltration of immune effector cells into tumours and convert the intrinsically immunosuppressive tumour microenvironment (TME) to an immunosupportive one. Immunotherapy relies on the accumulation and activity of immune effector cells within the TME, and immune responses and vascular normalization seem to be reciprocally regulated. Thus, combining antiangiogenic therapies and immunotherapies might increase the effectiveness of immunotherapy and diminish the risk of immune-related adverse effects. In this Perspective, we outline the roles of VEGF and ANG2 in tumour immune evasion and progression, and discuss the evidence indicating that antiangiogenic agents can normalize the TME. We also suggest ways that antiangiogenic agents can be combined with immune-checkpoint inhibitors to potentially improve patient outcomes, and highlight avenues of future research.

Mycobacterium tuberculosis remains a global threat to human health, yet the molecular mechanisms regulating immunity remain poorly understood. Cytokines can promote or inhibit mycobacterial survival inside macrophages and the underlying mechanisms represent potential targets for host-directed therapies. Here we show that cytokine-STAT signalling promotes mycobacterial survival within macrophages by deregulating lipid droplets via ATG2 repression. In Drosophila infected with Mycobacterium marinum, mycobacterium-induced STAT activity triggered by unpaired-family cytokines reduces Atg2 expression, permitting deregulation of lipid droplets. Increased Atg2 expression or reduced macrophage triglyceride biosynthesis, normalizes lipid deposition in infected phagocytes and reduces numbers of viable intracellular mycobacteria. In human macrophages, addition of IL-6 promotes mycobacterial survival and BCG-induced lipid accumulation by a similar, but probably not identical, mechanism. Our results reveal Atg2 regulation as a mechanism by which cytokines can control lipid droplet homeostasis and consequently resistance to mycobacterial infection in Drosophila.

Success of dendritic cell (DC) therapy in treating malignancies is depending on the DC capacity to attract immune effector cells, considering their reciprocal crosstalk is partially regulated by cell-contact-dependent mechanisms. Although critical for therapeutic efficacy, immune cell recruitment is a largely overlooked aspect regarding optimization of DC vaccination. In this paper we have made a head-to-head comparison of interleukin (IL)-15-cultured DCs and conventional IL-4-cultured DCs with regard to their proficiency in the recruitment of (innate) immune effector cells. Here, we demonstrate that IL-4 DCs are suboptimal in attracting effector lymphocytes, while IL15 DCs provide a favorable chemokine milieu for recruiting CD8+ T cells, natural killer (NK) cells and gamma delta (γδ) T cells. Gene expression analysis revealed that IL-15 DCs exhibit a high expression of chemokines involved in antitumor immune effector cell attraction, while IL-4 DCs display a more immunoregulatory profile characterized by the expression of Th2 and regulatory T cell-attracting chemokines. This is confirmed by functional data indicating an enhanced recruitment of granzyme B+ effector lymphocytes by IL-15 DCs, as compared to IL-4 DCs, and subsequent superior killing of tumor cells by the migrated lymphocytes. Elevated CCL4 gene expression in IL-15 DCs and lowered CCR5 expression on both migrated γδ T cells and NK cells, led to validation of increased CCL4 secretion by IL15 DCs. Moreover, neutralization of CCR5 prior to migration resulted in an important inhibition of γδ T cell and NK cell recruitment by IL-15 DCs. These findings further underscore the strong immunotherapeutic potential of IL-15 DCs.

Influenza A virus (IAV) matrix protein 2 (M2) plays multiple roles in the early and late phases of viral infection. Once synthesized, M2 is translocated to the endoplasmic reticulum (ER), travels to the Golgi apparatus, and is sorted at the trans-Golgi network (TGN) for transport to the apical plasma membrane, where it functions in virus budding. We hypothesized that M2 trafficking along with its secretory pathway must be finely regulated, and host factors could be involved in this process. However, no studies examining the role of host factors in M2 posttranslational transport have been reported. Here, we used a yeast two-hybrid (Y2H) system to screen for host proteins that interact with the M2 protein and identified transport protein particle complex 6A (TRAPPC6A) as a potential binding partner. We found that both TRAPPC6A and its N-terminal internal-deletion isoform, TRAPPC6A delta (TRAPPC6AΔ), interact with M2. Truncation and mutation analyses showed that the highly conserved leucine residue at position 96 of M2 is critical for mediating this interaction. The role of TRAPPC6AΔ in the viral life cycle was investigated by the knockdown of endogenous TRAPPC6AΔ with small interfering RNA (siRNA) and by generating a recombinant virus that was unable to interact with TRAPPC6A/TRAPPC6AΔ. The results indicated that TRAPPC6AΔ, through its interaction with M2, slows M2 trafficking to the apical plasma membrane, favors viral replication in vitro, and positively modulates virus virulence in mice., Importance: The influenza A virus M2 protein regulates the trafficking of not only other proteins but also itself along the secretory pathway. However, the host factors involved in the regulation of the posttranslational transport of M2 are largely unknown. In this study, we identified TRAPPC6A and its N-terminal internal-deletion isoform, TRAPPC6AΔ, as interacting partners of M2. We found that the leucine (L) residue at position 96 of M2 is critical for mediating this interaction, which leads us to propose that the high level of conservation of 96L is a consequence of M2 adaptation to its interacting host factor TRAPPC6A/TRAPPC6AΔ. Importantly, we discovered that TRAPPC6AΔ can positively regulate viral replication in vitro by modulating M2 trafficking to the plasma membrane., (Copyright © 2016 Zhu et al.)

Introduction: Lymphangiogenesis is the formation of new vessels from pre-existing lymphatic vessels. Data on lymphangiogenesis in the placenta of HIV-infected pre-eclamptics are sparse and the findings are conflicting. The aim of this novel study was to evaluate LYVE-1 immunoexpression in the placenta of HIV infected normotensive versus pre-eclamptic women., Methods: Placental tissue was obtained from normotensive and pre-eclamptic women stratified according to their HIV status. The pre-eclamptic group was divided into early (<34 weeks) and late (>34 weeks) onset. Immunohistochemistry utilized mouse anti-human LYVE-1 antibody and was morphometrically evaluated., Results: LYVE-1 immunostaining was localized within endothelium of the arterial supply and venous drainage of both conducting and exchange villi as well as within medial cells of arteries. LYVE-1 immunostained macrophage-like cells were observed within the fetal and maternal circulation. LYVE-1 immunoexpression was higher (p=0.0001) in HIV positive cohort, regardless of pregnancy and villous type. Irrespective of HIV status and pregnancy type, LYVE-1 immunoexpression was significantly elevated in the conducting compared to the exchange villi (p=0.01). LYVE-1 immunoexpression was higher in N and LOPE compared to EOPE groups for both conducting and exchange villi types respectively (p=0.0001 and p=0.006). There is a decrease of LYVE-1 expression in EOPE+ (conducting villi) and EOPE- (exchange villi) compared to N and LOPE subgroups., Conclusion: This study provides a novel insight into an up-regulation of LYVE-1 expression in the fetal circulation of conducting and exchange villi of HIV-infected pre-eclamptics., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The TALE-class homeoprotein MEIS1 specifically collaborates with HOXA9 to drive myeloid leukemogenesis. Although MEIS1 alone has only a moderate effect on cell proliferation in vitro, it is essential for the development of HOXA9-induced leukemia in vivo. Here, using murine models of leukemogenesis, we have shown that MEIS1 promotes leukemic cell homing and engraftment in bone marrow and enhances cell-cell interactions and cytokine-mediated cell migration. We analyzed global DNA binding of MEIS1 in leukemic cells as well as gene expression alterations in MEIS1-deficent cells and identified synaptotagmin-like 1 (Sytl1, also known as Slp1) as the MEIS1 target gene that cooperates with Hoxa9 in leukemogenesis. Replacement of SYTL1 in MEIS1-deficent cells restored both cell migration and engraftment. Further analysis revealed that SYTL1 promotes cell migration via activation of the CXCL12/CXCR4 axis, as SYTL1 determines intracellular trafficking of CXCR4. Together, our results reveal that MEIS1, through induction of SYTL1, promotes leukemogenesis and supports leukemic cell homing and engraftment, facilitating interactions between leukemic cells and bone marrow stroma.

Although the major autoantigens in classic pemphigus are desmogleins, sera from various types of pemphigus react with a number of other molecules, including desmocollins and plakin proteins. However, other novel pemphigus-related autoantigens remain to be identified. In this study, immunoblotting for serum from an atypical autoimmune bullous disease patient identified an unknown 175 kDa protein. Subsequent studies using two-dimensional gel electrophoresis, immunoblotting and mass-spectrometry identified the 175 kDa protein as early endosome antigen 1 (EEA1). This finding was confirmed by subsequent immunological studies, including indirect immunofluorescence of skin and cultured keratinocytes, two-dimensional gel electrophoresis and immunoblotting with anti-EEA1 polyclonal antibody, and preabsorption with EEA1 recombinant protein. Finally, we developed a novel BIOCHIP assay using full-length EEA1 recombinant protein to detect anti-EEA1 antibodies. However, none of 35 sera from various types of pemphigus showed anti-EEA1 antibodies in the BIOCHIP assay, with the exception of the serum from the index case. In addition, various findings in the index case did not suggest pathogenic role of anti-EEA1 autoantibodies. Therefore, although we successfully identified the 175 kDa protein reacted by a serum of an atypical pemphigus-like patient as EEA1, novel BIOCHIP study for other pemphigus sera indicated that EEA1 is not a common and pathogenic autoantigen in pemphigus., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Mutations in the autophagy gene EPG5 are linked to the multisystem human disease Vici syndrome, which is characterized in part by pulmonary abnormalities, including recurrent infections. We found that Epg5-deficient mice exhibited elevated baseline innate immune cellular and cytokine-based lung inflammation and were resistant to lethal influenza virus infection. Lung transcriptomics, bone marrow transplantation experiments, and analysis of cellular cytokine expression indicated that Epg5 plays a role in lung physiology through its function in macrophages. Deletion of other autophagy genes including Atg14, Fip200, Atg5, and Atg7 in myeloid cells also led to elevated basal lung inflammation and influenza resistance. This suggests that Epg5 and other Atg genes function in macrophages to limit innate immune inflammation in the lung. Disruption of this normal homeostatic dampening of lung inflammation results in increased resistance to influenza, suggesting that normal homeostatic mechanisms that limit basal tissue inflammation support some infectious diseases., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background/aims: Dysfunction of autophagy has been associated with loss of intestinal homeostasis. Lipopolysaccharide (LPS) from Gram-negative bacteria is known to be a major initiator of intestinal epithelial cell (IEC) autophagy. Although probiotics have been recognized to be involved in many therapeutic properties and participate in host defense responses, the molecular mechanisms by which probiotics exert these positive effects remain unknown. This study assessed the effect of probiotics on LPS-induced physical barrier dysfunction and the underlying mechanism of probiotic action in IECs with a focus on autophagy., Methods: A LPS-induced autophagic model was established in rat IEC18 cells wherein cells were treated with culture medium supernatants of Bifidobacteria following LPS intervention at indicated times. Autophagosomes in IEC18 cells were visualized by confocal microscopy after transfection with a tandem GFP-mCherry-LC3 construct and also by transmission electron microscopy. Autophagy-associated protein levels were analyzed by western blot and transepithelial electrical resistance (TEER) was measured using an epithelial voltohmmeter., Results: Probiotic treatment could effectively inhibit LPS-induced autophagy, as evidenced by the decreased ratio of microtubule-associated light chain 3 (LC3)-II/LC3-I, fewer autophagic vacuoles, and reduced punctate distribution of GFP-mCherry-LC3. In addition, probiotics prevented chloroquine (CQ) inhibition of autophagic flux and autophagolysosomal fusion as indicated by a failure to recruit LAMP1 and cathepsin D to lysosomes. Interestingly, ATG16L1 knockdown did not inhibit the effect of probiotics on LPS-induced autophagy. Furthermore, the diminished barrier function could be prevented by probiotics., Conclusions: We provide evidence that autophagy mediation by probiotics may be involved in enteroprotection against LPS-induced intestinal epithelial toxicity, and could serve as a novel mechanism through which probiotics promote and maintain gut homeostasis., (© 2016 The Author(s) Published by S. Karger AG, Basel.)

Objective: Giant cell arteritis (GCA) is pathologically characterized by dysfunctional angiogenesis and inflammatory cell infiltration. Acute-phase serum amyloid A (A-SAA) is an acute-phase reactant, but is also produced at sites of inflammation and may contribute to vascular inflammation in atherosclerosis. This study was undertaken to examine the effect of A-SAA on proinflammatory pathways and angiogenesis in GCA, using a novel ex vivo temporal artery tissue explant model., Methods: Serum A-SAA levels were measured by enzyme-linked immunosorbent assay (ELISA). Temporal artery explants and peripheral blood mononuclear cell (PBMC) cultures were established from patients with GCA. Temporal artery explant morphology, viability, and spontaneous release of proinflammatory mediators following 24-hour culture were assessed by hematoxylin and eosin, calcein viability staining, and ELISA. Temporal artery explants and PBMC cultures were stimulated with A-SAA (10 μg/ml), and interleukin-6 (IL-6), IL-8, vascular endothelial growth factor, Ang2, and matrix metalloproteinase 2 (MMP-2)/MMP-9 were quantified by ELISA and gelatin zymography. The effect of conditioned medium from temporal artery explants on angiogenesis was assessed using endothelial cell Matrigel tube-formation assays. Temporal artery explants were also embedded in Matrigel, and myofibroblast outgrowth was assessed., Results: Serum A-SAA levels were significantly higher in GCA patients versus healthy controls (P < 0.0001). Intact tissue morphology, cell viability, and spontaneous cytokine secretion were demonstrated in temporal artery explants. A-SAA treatment induced a significant increase in the levels of IL-6 and IL-8 from temporal artery explants (P < 0.05) and IL-8 from PBMCs (P < 0.05) compared to basal conditions. Conditioned medium from A-SAA-treated explants significantly induced angiogenic tube formation (P < 0.05 versus basal controls). Finally, A-SAA induced myofibroblast outgrowth and MMP-9 activation., Conclusion: Our findings demonstrate a functional role for A-SAA in regulating temporal artery inflammation, angiogenesis, and invasion, all key processes in the pathogenesis of GCA., (© 2015, American College of Rheumatology.)

Context: Central diabetes insipidus (CDI) can be caused by several diseases, but in about half of the patients the etiological diagnosis remains unknown. Lymphocytic infundibulo-neurohypophysitis (LINH) is an increasingly recognized entity among cases of idiopathic CDI; however, the differential diagnosis from other pituitary diseases including tumors can be difficult because of similar clinical and radiological manifestations. The definite diagnosis of LINH requires invasive pituitary biopsy., Objective: The study was designed to identify the autoantigen(s) in LINH and thus develop a diagnostic test based on serum autoantibodies., Design: Rat posterior pituitary lysate was immunoprecipitated with IgGs purified from the sera of patients with LINH or control subjects. The immunoprecipitates were subjected to liquid chromatography-tandem mass spectrometry to screen for pituitary autoantigens of LINH. Subsequently, we made recombinant proteins of candidate autoantigens and analyzed autoantibodies in serum by Western blotting., Results: Rabphilin-3A proved to be the most diagnostically useful autoantigen. Anti-rabphilin-3A antibodies were detected in 22 of the 29 (76%) patients (including 4 of the 4 biopsy-proven samples) with LINH and 2 of 18 (11.1%) patients with biopsy-proven lymphocytic adeno-hypophysitis. In contrast, these antibodies were absent in patients with biopsy-proven sellar/suprasellar masses without lymphocytic hypophysitis (n = 34), including 18 patients with CDI. Rabphilin-3A was expressed in posterior pituitary and hypothalamic vasopressin neurons but not anterior pituitary., Conclusions: These results suggest that rabphilin-3A is a major autoantigen in LINH. Autoantibodies to rabphilin-3A may serve as a biomarker for the diagnosis of LINH and be useful for the differential diagnosis in patients with CDI.

Brucella species replicate within host cells in the form of endoplasmic reticulum (ER)-derived vacuoles. The mechanisms by which the bacteria are sequestered into such vacuoles and obtain a continuous membrane supply for their replication remain to be elucidated. In the present study, we provided several lines of evidence that demonstrate the mechanism by which B. abortus acquires the ER-derived membrane. First, during Brucella infection, the IRE1 pathway, but not the PERK and ATF6 pathways, of the unfolded protein response (UPR) was activated in a time-dependent manner, and the COPII vesicle components Sar1, Sec23, and Sec24D were upregulated. Second, a marked accretion of ER-derived vacuoles was observed around replicating bacteria using fluorescent microscopy and electron microscopy. Third, we identified a novel host factor, Yip1A, for the activation of the IRE1 pathway in response to both tunicamycin treatment and infection with B. abortus. We found that Yip1A is responsible for the phosphorylation of IRE1 through high-order assembly of Ire1 molecules at ER exit sites (ERES) under the UPR conditions. In Yip1A-knockdown cells, B. abortus failed to generate the ER-derived vacuoles, and remained in endosomal/lysosomal compartments. These results indicate that the activation of the IRE1 pathway and the subsequent formation of ER-derived vacuoles are critical for B. abortus to establish a safe replication niche, and that Yip1A is indispensable for these processes. Furthermore, we showed that the autophagy-related proteins Atg9 and WIPI1, but not DFCP1, were required for the biogenesis of the ER-derived membrane compartments. 　On the basis of our findings, we propose a model for intracellular Brucella replication that exploits the host UPR and ER-derived vacuole formation machineries, both of which depend on Yip1A-mediated IRE1 activation.

The cellular prion protein (PrP(C)) is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein on the cell surface. Previous studies have demonstrated contradictory roles for PrP(C) in connection with the phagocytic ability of macrophages. In the present work, we investigated the function of PrP(C) in phagocytosis and cytokine expression in bone marrow-derived macrophages infected with Escherichia coli. E. coli infection induced an increase in the PRNP mRNA level. Knockout of PrP(C) promoted bacterial uptake; upregulated Rab5, Rab7, and Eea1 mRNA expression; and increased the recruitment of lysosomal-associated membrane protein-2 to phagosomes, suggesting enhanced microbicidal activity. Remarkably, knockout of PrP(C) suppressed the proliferation of internalized bacteria and increased the expression of cytokines such as interleukin-1β. Collectively, our data reveal an important role of PrP(C) as a negative regulator for phagocytosis, phagosome maturation, cytokine expression, and macrophage microbicidal activity.

Zona pellucida-based induction of acrosome reaction (AR) is a popular and well-accepted hypothesis. However, this hypothesis is being challenged in recent years and it has been proposed that the cumulus cells might be the site of AR. In our previous study, we reported the presence of a synaptic protein Liprin α3 on sperm acrosome, and proposed its role in AR. This study was designed to understand the role of Liprin α3 and its interacting proteins in regulation of AR. It is observed that the presence of anti-Liprin α3 antibody inhibits the process of AR. Colocalization experiments demonstrate the coexistence of leucocyte antigen related (LAR) protein, Rab-interacting molecule (RIM) and Liprin α3 on sperm acrosome thereby completing the identification of all the members of RIM/MUNC/Rab3A/liprinα complex required for membrane fusion. This study demonstrates the effect of LAR ligands such as Syndecans, Nidogens and LAR wedge domain peptide on AR. We could see an increase in AR in presence of these ligands. On the basis of these data, we speculate that in presence of ligands or wedge peptide, LAR undergoes dimerization leading to inhibition of phosphatase activity and increase in AR. The presence of one of the ligands Syndecan-1 on cumulus cells led us to hypothesize that it is Syndecan which induces AR in vivo and thus another site of AR could lie in cumulus., (© 2013 American Society of Andrology and European Academy of Andrology.)

Purpose of Review: The purpose of this review is to summarize pathogenic mechanisms and clinical implications of the most illustrative genetic entities of congenital neutropenia syndromes., Recent Findings: Congenital neutropenia comprise monogenetic entities with or without additional immunologic and extrahaematopoietic syndromatic features. Continuous careful explorations of known entities such as ELANE, GFI1, HAX1, G6PC3 deficiency and XLN help to define principles controlling differentiation and function of neutrophil granulocytes. Furthermore, the identification of novel genetic defects associated with congenital neutropenia, such as VPS45 deficiency, broadens our understanding of neutrophil biology. Pathogenic mechanisms imply protein and vesicle mistrafficking, endoplasmic reticulum stress, the unfolded protein response, destabilization of the mitochondrial membrane potential, disturbed energy metabolism, dysglycosylation and deregulated actin polymerization., Summary: Advanced genetic and biochemical techniques have helped to expand our knowledge of congenital neutropenia syndromes. Known and novel genetic entities shed light on fundamental biological processes important for the homeostatis and functioning not only of the neutrophil granulocyte but as well of the entire haematopoietic system. Furthermore, treatment decisions become more tailored and might pave the road towards personalized molecular medicine.

Purpose: Inflammation and immune cells regulate choroidal neovascularization (CNV) and could become therapeutic targets in age-related macular degeneration (AMD). Lymphangiogenesis is a key component of various inflammatory diseases. Whether lymphangiogenesis and lymph node-mediated immunity are involved in the pathogenesis of AMD is not understood., Methods: To investigate lymphangiogenesis in CNV, we generated CNV in animals by laser and studied surgically removed CNV membranes from uveitis and AMD patients. Immunohistochemistry was performed with lymphatic vessel endothelial hyaluronate receptor 1 (LYVE-1) and podoplanin antibodies. VEGF-C and VEGFR-3 expressions were examined with immunohistochemistry and Western blotting. To examine the role of lymph node in CNV, we lasered lymphotoxin alpha-deficient mice (LTα-/-) and measured the CNV volume., Results: Immunohistochemistry showed that LYVE-1(+) macrophages infiltrated in acutely induced CNV, although lymphatic tubes did not form. CNV membranes from patients did not show LYVE-1(+)podoplanin(+) vessels, suggesting the lack of lymphangiogenesis in AMD and uveitis. Western blots and immunostaining revealed VEGF-C and VEGFR-3 expression in CNV lesions, mainly in macrophages and angiogenic endothelial cells. Using fluorescent microsphere tracers, we show a path for cellular migration from the eye to the cervical lymph nodes (LNs) during CNV. However, CNV injury did not cause LN swelling. CNV volume did not differ between wild-type and LN-deficient mice, suggesting that LN is not a key component of early CNV formation., Conclusions: Laser-induced CNV is not primarily dependent on acquired immunity, nor does the fundus injury affect peripheral LNs. Our results reveal a previously unknown cellular connection between the ocular fundus and the cervical LNs. This connection that in function resembles lymphatics is actively utilized in CNV.

Phagocytes such as dendritic cells (DC) and macrophages employ phagocytosis to take up pathogenic bacteria into phagosomes, digest the bacteria and present the bacteria-derived peptide antigens to the adaptive immunity. Hence, efficient antigen presentation depends greatly on a well-regulated phagocytosis process. Lipids, particularly phosphoinositides, are critical components of the phagosomes. Phosphatidylinositol-3,4,5-triphosphate [PI(3,4,5)P3 ] is formed at the phagocytic cup, and as the phagosome seals off from the plasma membrane, rapid disappearance of PI(3,4,5)P3 is accompanied by high levels of phosphatidylinositol-3-phosphate (PI3P) formation. The sorting nexin (SNX) family consists of a diverse group of Phox-homology (PX) domain-containing cytoplasmic and membrane-associated proteins that are potential effectors of phosphoinositides. We hypothesized that SNX3, a small sorting nexin that contains a single PI3P lipid-binding PX domain as its only protein domain, localizes to phagosomes and regulates phagocytosis in DC. Our results show that SNX3 recruits to nascent phagosomes and silencing of SNX3 enhances phagocytic uptake of bacteria by DC. Furthermore, SNX3 competes with PI3P lipid-binding protein, early endosome antigen-1 (EEA1) recruiting to membranes. Our results indicate that SNX3 negatively regulates phagocytosis in DC possibly by modulating recruitment of essential PI3P lipid-binding proteins of the phagocytic pathways, such as EEA1, to phagosomal membranes., (© 2012 Blackwell Publishing Ltd.)

Abstract LYVE-1 is a marker expressed by lymphatic endothelial cells (LECs) that line the lymphatic endothelium. Through studies designed to examine potential changes in expression of LYVE-1 in cynomolgus macaque colon tissues during the course of simian immunodeficiency virus (SIV) infection, we discovered that LYVE-1 was expressed by heterogenous populations of cells. As revealed by in situ hybridization (ISH), LYVE-1 mRNA levels in colon were decreased in macaques with AIDS compared with acutely infected or uninfected macaques. In the submucosal layer of the colon, approximately half of the LYVE-1-expressing cells co-expressed the dendritic cell (DC) marker, DC-SIGN/CD209, and this percentage did not change appreciably during infection. Subsets of cells expressing LYVE-1 also co-expressed macrophage markers, such as CD68 and the macrophage mannose receptor (MMR)/CD206, in both the colon and lymph nodes. LECs, DCs, and macrophages that co-expressed LYVE-1 were observed in colon and lymph node from uninfected, healthy animals as well as in tissues with SIV-driven inflammation. These findings provide further definition of the phenotypic overlap between LECs and antigen presenting cells, reveal the heterogeneity within the population of cells expressing the lymphatic marker LYVE-1, and show that SIV modulates this population of cells in a mucosal surface across which the virus is acquired.

WASH is an Arp2/3 activator of the Wiskott-Aldrich syndrome protein superfamily that functions during endosomal trafficking processes in collaboration with the retromer and sorting nexins, but its in vivo function has not been examined. To elucidate the physiological role of WASH in T cells, we generated a WASH conditional knockout (WASHout) mouse model. Using CD4(Cre) deletion, we found that thymocyte development and naive T cell activation are unaltered in the absence of WASH. Surprisingly, despite normal T cell receptor (TCR) signaling and interleukin-2 production, WASHout T cells demonstrate significantly reduced proliferative potential and fail to effectively induce experimental autoimmune encephalomyelitis. Interestingly, after activation, WASHout T cells fail to maintain surface levels of TCR, CD28, and LFA-1. Moreover, the levels of the glucose transporter, GLUT1, are also reduced compared to wild-type T cells. We further demonstrate that the loss of surface expression of these receptors in WASHout cells results from aberrant accumulation within the collapsed endosomal compartment, ultimately leading to degradation within the lysosome. Subsequently, activated WASHout T cells experience reduced glucose uptake and metabolic output. Thus, we found that WASH is a newly recognized regulator of TCR, CD28, LFA-1, and GLUT1 endosome-to-membrane recycling. Aberrant trafficking of these key T cell proteins may potentially lead to attenuated proliferation and effector function.

Variations in lipopolysaccharide (LPS), a bacterial outer membrane component, determine virulence of the obligate intracellular bacterium Coxiella burnetii, but the underlying mechanisms are unknown. We find that while avirulent C. burnetii LPS (avLPS) stimulates host p38α-MAPK signaling required for proper trafficking of bacteria containing compartments to lysosomes for destruction, pathogenic C. burnetii LPS (vLPS) does not. The defect in vLPS and pathogenic C. burnetii targeting to degradative compartments involves an antagonistic engagement of TLR4 by vLPS, lack of p38α-MAPK-driven phosphorylation, and block in recruitment of the homotypic fusion and protein-sorting complex component Vps41 to vLPS-containing vesicles. An upstream activator of p38α-MAPK or phosphomimetic mutant Vps41-S796E expression overrides the inhibition, allowing vLPS and pathogenic C. burnetii targeting to phagolysosomes. Thus, p38α-MAPK and its crosstalk with Vps41 play a central role in trafficking bacteria to phagolysosomes. Pathogenic C. burnetii has evolved LPS variations to evade this host response and thrive intracellularly., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Mast cell (MC) granules contain large amounts of proteases of the chymase, tryptase and carboxypeptidase A (MC-CPA) type that are stored in complex with serglycin,a proteoglycan with heparin side chains. Hence, serglycinprotease complexes are released upon MC degranulation and may influence local inflammation. Here we explored the possibility that a serglycin-protease axis may regulate levels of IL-13, a cytokine involved in allergic asthma. Indeed, we found that wild-type MCs efficiently degraded exogenous or endogenously produced IL-13 upon degranulation,whereas serglycin −/− MCs completely lacked this ability.Moreover, MC-mediated IL-13 degradation was blocked both by a serine protease inhibitor and by a heparin antagonist,which suggests that IL-13 degradation is catalyzed by serglycin-dependent serine proteases and that optimal IL-13 degradation is dependent on both the serglycin and the protease component of the serglycin-protease complex.Moreover, IL-13 degradation was abrogated in MC-CPA −/−MC cultures, but was normal in cultures of MCs with an inactivating mutation of MC-CPA, which suggests that the IL-13-degrading serine proteases rely on MC-CPA protein.Together, our data implicate a serglycin-serine protease axis in the regulation of extracellular levels of IL-13. Reduction of IL-13 levels through this mechanism possibly can provide a protective function in the context of allergic inflammation.

The authors established a chromogen-based, double immunolabeling method using antibodies from the same species without any unwanted cross-reactivity. In addition, time-consuming staining steps were shortened by using polymer-based secondary antibodies. Taking advantage of the nature of the chromogen 3-amino-9-ethylcarbazole (AEC), which is used as a horseradish peroxidase substrate for antibody detection, the AEC-derived signals in the first color development were easily eliminated by alcohol treatment. Therefore, the signals from the first staining did not interfere with those from the subsequent second staining, which used the chromogen 3,3'-diaminobenzidine. The co-localization of antigens within the same cell could be confirmed using this method, because cell images of the individual dye staining steps could be obtained and developed. The images from each step could be expressed in pseudo-colors in a dark field by using a computer. As a result, merged images could be constructed that resembled the images acquired by the fluorescent immunolabeling technique. The resolution of this method enabled analysis of the coexpression of two antigens in the same cell in the same section. The authors have named this staining technique the elucidation of the coexpression of two antigens in a cell using antibodies from the same species (ECSS).

TMF/ARA160 is a Golgi-associated protein with several cellular functions, among them direction of the NF-κB subunit, p65 RelA, to ubiquitination and proteasomal degradation in stressed cells. We sought to investigate the role of TMF/ARA160 under imposed stress conditions in vivo. TMF(-/-) and wild-type (WT) mice were treated with the ulcerative agent dextran sulfate sodium (DSS), and the severity of the inflicted acute colitis was determined. TMF(-/-) mice were found to be significantly less susceptible to DSS-induced colitis, with profoundly less bacterial penetration into the colonic epithelia. Surprisingly, unlike in WT mice, no bacterial colonies were visualized in colons of healthy untreated TMF(-/-) mice, indicating the constitutive resistance of TMF(-/-) colonic mucus to bacterial retention and penetration. Gene expression analysis of colon tissues from unchallenged TMF(-/-) mice revealed 5-fold elevated transcription of the muc2 gene, which encodes the major component of the colonic mucus gel, the MUC2 mucin. Accordingly, the morphology of the colonic mucus in TMF(-/-) mice was found to differ from the mucus structure in WT colons. The NF-κB subunit, p65, a well known transcription inducer of muc2, was up-regulated significantly in TMF(-/-) intestinal epithelial cells. However, this did not cause spontaneous inflammation or increased colonic crypt cell proliferation. Collectively, our findings demonstrate that absence of TMF/ARA160 renders the colonic mucus refractory to bacterial colonization and the large intestine less susceptible to the onset of colitis.

Cross-presentation is the presentation by MHC class I of antigenic peptides from exogenous proteins that have been internalized and processed by professional antigen-presenting cells, e.g. dendritic cells. We have investigated the influence of particle size and antigen load on cross-presentation following antigen delivery on microspheres (MS). Cross-presentation from small particles (0·8-μm) is sensitive to proteasome inhibition and the blockade of endoplasmic reticulum-resident MHC class I complex export, whereas cross-presentation from larger particles (aggregated clumps of 0·8-μm MS) is resistant to these antagonists. This observation may have been overlooked previously, because of the heterogeneity of particle size and MS uptake in unsorted dendritic cell populations. Larger particles carry more antigen, but we show that antigen load does not influence the cross-presentation pathway used. Whereas early endosome autoantigen 1 (EEA1) could be observed in all phagosomes, we observed endoplasmic reticulum SNARE of molecular weight 24 000 (ERS24) and cathepsin S in association with 3·0-μm and aggregated 0·8-μm MS, but not individual 0·8-μm MS. A potential mechanism underlying our observations may be the activation of β-catenin by disruption of E-cadherin-mediated adhesion. Activated β-catenin was detected in the cytoplasm of cells after phagocytosis of MS (highest levels for the largest particles). We propose that particle size can direct the use of different pathways for the cross-presentation of an identical antigen. Furthermore, these pathways have differing yields of MHC class I-peptide complexes, which is an important variable in designing vaccination strategies for maximal antigen expression and CD8(+) T-cell priming., (© 2012 The Authors. Immunology © 2012 Blackwell Publishing Ltd.)

A proline to serine substitution at position 56 in the gene encoding vesicle-associated membrane protein-associated protein B (VAPB) causes some dominantly inherited familial forms of motor neuron disease including amyotrophic lateral sclerosis (ALS) type-8. VAPB is an integral endoplasmic reticulum (ER) protein whose amino-terminus projects into the cytosol. Overexpression of ALS mutant VAPBP56S disrupts ER structure but the mechanisms by which it induces disease are not properly understood. Here we show that VAPB interacts with the outer mitochondrial membrane protein, protein tyrosine phosphatase-interacting protein 51 (PTPIP51). ER and mitochondria are both stores for intracellular calcium (Ca(2+)) and Ca(2+) exchange between these organelles occurs at regions of ER that are closely apposed to mitochondria. These are termed mitochondria-associated membranes (MAM). We demonstrate that VAPB is a MAM protein and that loss of either VAPB or PTPIP51 perturbs uptake of Ca(2+) by mitochondria following release from ER stores. Finally, we demonstrate that VAPBP56S has altered binding to PTPIP51 and increases Ca(2+) uptake by mitochondria following release from ER stores. Damage to ER, mitochondria and Ca(2+) homeostasis are all seen in ALS and we discuss the implications of our findings in this context.

Background: Wiskott-Aldrich Syndrome (WASP) family proteins participate in many cellular processes involving rearrangements of the actin cytoskeleton. To the date, four WASP subfamily members have been described in Drosophila: Wash, WASp, SCAR, and Whamy. Wash, WASp, and SCAR are essential during early Drosophila development where they function in orchestrating cytoplasmic events including membrane-cytoskeleton interactions. A mutant for Whamy has not yet been reported., Results: We generated monoclonal antibodies that are specific to Drosophila Wash, WASp, SCAR, and Whamy, and use these to describe their spatial and temporal localization patterns. Consistent with the importance of WASP family proteins in flies, we find that Wash, WASp, SCAR, and Whamy are dynamically expressed throughout oogenesis and embryogenesis. For example, we find that Wash accumulates at the oocyte cortex. WASp is highly expressed in the PNS, while SCAR is the most abundantly expressed in the CNS. Whamy exhibits an asymmetric subcellular localization that overlaps with mitochondria and is highly expressed in muscle., Conclusions: All four WASP family members show specific expression patterns, some of which reflect their previously known roles and others revealing new potential functions. The monoclonal antibodies developed offer valuable new tools to investigate how WASP family proteins regulate actin cytoskeleton dynamics., (Copyright © 2012 Wiley Periodicals, Inc.)

Targeting antigens to dendritic cell (DC)-specific receptors, such as DC-SIGN, induces potent T cell-mediated immune responses. DC-SIGN is a transmembrane C-type lectin receptor with a long extracellular neck region and a carbohydrate recognition domain (CRD). Thus far, only antibodies binding the CRD have been used to target antigens to DC-SIGN. We evaluated the endocytic pathway triggered by antineck antibodies as well as their intracellular routing and ability to induce CD8(+) T-cell activation. In contrast to anti-CRD antibodies, antineck antibodies induced a clathrin-independent mode of DC-SIGN internalization, as demonstrated by the lack of colocalization with clathrin and the observation that silencing clathrin did not affect antibody internalization in human DCs. Interestingly, we observed that anti-neck and anti-CRD antibodies were differentially routed within DCs. Whereas anti-CRD antibodies were mainly routed to late endosomal compartments, anti-neck antibodies remained associated with early endosomal compartments positive for EEA-1 and MHC class I for up to 2 hours after internalization. Finally, cross-presentation of protein antigen conjugated to antineck antibodies was approximately 1000-fold more effective than nonconjugated antigen. Our studies demonstrate that anti-neck antibodies trigger a distinct mode of DC-SIGN internalization that shows potential for targeted vaccination strategies.

Major histocompatibility complex (MHC) class II (MHCII) is constitutively expressed by immature dendritic cells (DC), but has a short half-life as a consequence of its transport to and degradation in lysosomes. For its transfer to lysosomes, MHCII is actively sorted to the intraluminal vesicles (ILV) of multivesicular bodies (MVB), a process driven by its ubiquitination. ILV have, besides their role as an intermediate compartment in lysosomal transfer, also been proposed to function as a site for MHCII antigen loading and temporal storage. In that scenario, DC would recruit antigen-loaded MHCII to the cell surface in response to a maturation stimulus by allowing ILV to fuse back with the MVB delimiting membrane. Other studies, however, explained the increase in cell surface expression during DC maturation by transient upregulation of MHCII synthesis and reduced sorting of newly synthesized MHCII to lysosomes. Here, we have characterized the relative contributions from the biosynthetic and endocytic pathways and found that the vast majority of antigen-loaded MHCII that is stably expressed at the plasma membrane by mature DC is synthesized after exposure to inflammatory stimuli. Pre-existing endosomal MHCII contributed only when it was not yet sorted to ILV at the moment of DC activation. Together with previous records, our current data are consistent with a model in which passage of MHCII through ILV is not required for antigen loading in maturing DC and in which sorting to ILV in immature DC provides a one-way ticket for lysosomal degradation., (© 2011 John Wiley & Sons A/S.)

Serglycin (SG) is a proteoglycan expressed by hematopoietic cells and is constitutively secreted by multiple myeloma (MM) cells. SG participates in the regulation of various inflammatory events. We found that SG secreted by human MM cell lines inhibits both the classical and lectin pathways of complement, without influencing alternative pathway activity. The inhibitory effect of SG is due to direct interactions with C1q and mannose-binding lectin (MBL). C1q-binding is mediated through the glycosaminoglycan moieties of SG, whereas MBL binds additionally to SG protein core. Interactions between SG and C1q as well as MBL are diminished in the presence of chondroitin sulfate type E. In addition, we localized the SG-binding site to the collagen-like stalk of C1q. Interactions between SG and C1q as well as MBL are ionic in character and only the interaction with MBL was found to be partially dependent on the presence of calcium. We found the serum levels of SG to be elevated in patients with MM compared to healthy controls. Moreover, we found that SG expressed from myeloma plasma cells protects these cells from complement activation induced by treatment with anti-thymocyte immunoglobulins. This might protect myeloma cells during immunotherapy and promote survival of malignant cells., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

When evaluating candidate prophylactic HIV and cancer vaccines, intracellular cytokine staining (ICS) assays that measure the frequency and magnitude of antigen-specific T-cell subsets are one tool to monitor immunogen performance and make product advancement decisions. To assess the inter-laboratory assay variation among multiple laboratories testing vaccine candidates, the NIH/NIAID/DAIDS in collaboration with BD Biosciences implemented an ICS Quality Assurance Program (QAP). Seven rounds of testing have been conducted in which 16 laboratories worldwide participated. In each round, IFN-γ, IL-2 and/or TNF-α responses in CD4+ and CD8+ T-cells to CEF or CMV pp65 peptide mixes were tested using cryopreserved peripheral blood mononuclear cells (PBMC) from CMV seropositive donors. We found that for responses measured above 0.2%, inter-laboratory %CVs were, on average, 35%. No differences in inter-laboratory variation were observed if a 4-color antibody cocktail or a 7-color combination was used. Moreover, the data allowed identification of important sources of variability for flow cytometry-based assays, including: number of collected events, gating strategy and instrument setup and performance. As a consequence, in this multi-site study we were able to define pass and fail criteria for ICS assays, which will be adopted in the subsequent rounds of testing and could be easily extrapolated to QAP for other flow cytometry-based assays., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Regulation of endosomal trafficking by Rab GTPases depends on selective interactions with multivalent effectors, including EEA1 and Rabenosyn-5, which facilitate endosome tethering, sorting, and fusion. Both EEA1 and Rabenosyn-5 contain a distinctive N-terminal C(2)H(2) zinc finger that binds Rab5. How these C(2)H(2) zinc fingers recognize Rab GTPases remains unknown. Here, we report the crystal structure of Rab5A in complex with the EEA1 C(2)H(2) zinc finger. The binding interface involves all elements of the zinc finger as well as a short N-terminal extension but is restricted to the switch and interswitch regions of Rab5. High selectivity for Rab5 and, to a lesser extent Rab22, is observed in quantitative profiles of binding to Rab family GTPases. Although critical determinants are identified in both switch regions, Rab4-to-Rab5 conversion-of-specificity mutants reveal an essential requirement for additional substitutions in the proximal protein core that are predicted to indirectly influence recognition through affects on the structure and conformational stability of the switch regions.