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Standard chemotherapy agents, including carboplatin, have known immunogenic properties. We sought to determine how carboplatin may influence lymphocyte trafficking to tumor sites. Murine models of ovarian cancer were utilized to examine lymphocyte trafficking with common clinically used agents including carboplatin, anti-PD-1 antibody, or anti-VEGFR-2 antibody. Adhesion interactions of lymphocytes with tumor vasculature were measured using intravital microscopy, lymphocyte homing with immunohistochemistry, and treatment groups followed for overall survival. Carboplatin chemotherapy profoundly alters the tumor microenvironment to promote lymphocyte adhesive interactions with tumor vasculature and resultant improvement in lymphocyte trafficking. The measured results seen with carboplatin in the tumor microenvironment were superior to anti-PD-1 treatment or anti-VEGFR-2 which may have contributed to increased overall survival in carboplatin treated groups. These novel findings suggest a role for chemotherapeutic agents to broadly influence anti-tumor immune responses beyond the induction of immunogenic tumor cell death. • Carboplatin promotes lymphocyte adhesive interactions with tumor vasculature and increases lymphocyte trafficking. • Carboplatin was associated with increased vessel diameters and percentage of viable tumor vessels supporting blood flow. • The influence of carboplatin on the tumor microenvironment suggests synergy with existing immunotherapy approaches. [ABSTRACT FROM AUTHOR]

Krüppel-like factor 2 (KLF2) is a transcription factor with significant roles in development, maturation, differentiation, and proliferation of several cell types. In immune cells, KLF2 regulates maturation and trafficking of lymphocytes and monocytes. KLF2 participates in regulation of the nuclear factor kappa-lightchain-enhancer of activated B cells (NF-kB) pathway. Although pulmonary arterial hypertension (PAH) related to KLF2 genetic variant has been suggested, genetic role of KLF2 associated with immune dysregulation has not been described. We identified a family whose members suffered from lymphopenia, autoimmunity, and malignancy. Whole exome sequencing revealed a KLF2 p.(Glu318Argfs*87) mutation disrupting the highly conserved zinc finger domain. We show a reduced amount of KLF2 protein, defective nuclear localization and altered protein-protein interactome. The phenotypically variable positive cases presented with B and T cell lymphopenia and abnormalities in B and T cellmaturation including low naive T cell counts and low CD27+IgD-IgM-switched memory B cells. KLF2 target gene (CD62L) expression was affected. Although the percentage of (CD25+FOXP3+, CD25+CD127-) regulatory T cells (Treg) was high, the naive Treg cells (CD45RA+) were absent. Serum IgG1 levels were low and findings in one case were consistent with common variable immunodeficiency (CVID). Transcription of NF-kb pathway genes and p65/RelA phosphorylation were not significantly affected. Inflammasome activity, transcription of genes related with JAK/STAT pathway and interferon signature were also comparable to controls. Evidence of PAH was not found. In conclusion, KLF2 variant may be associated with familial immune dysregulation. Although the KLF2 deficient family members in our study suffered from lymphopenia, autoimmunity or malignancy, additional study cohorts are required to confirm our observations. [ABSTRACT FROM AUTHOR]

Krüppel-like factor 2 (KLF2) is a transcription factor with significant roles in development, maturation, differentiation, and proliferation of several cell types. In immune cells, KLF2 regulates maturation and trafficking of lymphocytes and monocytes. KLF2 participates in regulation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Although pulmonary arterial hypertension (PAH) related to KLF2 genetic variant has been suggested, genetic role of KLF2 associated with immune dysregulation has not been described. We identified a family whose members suffered from lymphopenia, autoimmunity, and malignancy. Whole exome sequencing revealed a KLF2 p.(Glu318Argfs*87) mutation disrupting the highly conserved zinc finger domain. We show a reduced amount of KLF2 protein, defective nuclear localization and altered protein-protein interactome. The phenotypically variable positive cases presented with B and T cell lymphopenia and abnormalities in B and T cell maturation including low naive T cell counts and low CD27+IgD-IgM- switched memory B cells. KLF2 target gene (CD62L) expression was affected. Although the percentage of (CD25+FOXP3+, CD25+CD127-) regulatory T cells (Treg) was high, the naive Treg cells (CD45RA+) were absent. Serum IgG1 levels were low and findings in one case were consistent with common variable immunodeficiency (CVID). Transcription of NF-κβ pathway genes and p65/RelA phosphorylation were not significantly affected. Inflammasome activity, transcription of genes related with JAK/STAT pathway and interferon signature were also comparable to controls. Evidence of PAH was not found. In conclusion, KLF2 variant may be associated with familial immune dysregulation. Although the KLF2 deficient family members in our study suffered from lymphopenia, autoimmunity or malignancy, additional study cohorts are required to confirm our observations.

CD4dim CD8bright T cells are a mature population of CD8+ T cells that upon activation upregulate CD4 dimly on their surface. Expression of CD4 on these cells suggests that they can be an additional source of HIV neuroinvasion and persistence in the brain. We used HIV-infected NOD/SCID/IL-2rcγ-/- (NSG) humanized mice to track CD4dim CD8bright T cell homing to the brain and define their role in HIV dissemination into the brain. We report here that CD4dim CD8bright T cells are found in the brain at a median frequency of 2.6% and in the spleen at median frequency of 7.6% of CD3+ T cells. In the brain, 10 to 20% of CD4dim CD8bright T cells contain integrated provirus, which is infectious as demonstrated by viral outgrowth assay. CD4dim CD8bright T cells in the brain exhibited significantly higher expression of the brain homing receptors CX3CR1 and CXCR3 in comparison to their single-positive CD8+ T cell counterpart. Blocking lymphocyte trafficking into the brain of humanized mice via anti-VLA4 and anti-LFA1 antibodies reduced CD4dim CD8bright T cell trafficking into the brain by 60% and diminished brain HIV proviral DNA by 72%. Collectively, our findings demonstrate that CD4dim CD8bright T cells can home to the brain and support productive HIV replication. These studies also reveal for the first time that CD4dim CD8bright T cells are capable of HIV neuroinvasion and are a reservoir for HIV. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells protect against intracellular infection and cancer. These properties are exploited in oncolytic virus (OV) therapy, where antiviral responses enhance anti‐tumour immunity. We have analysed the mechanism by which reovirus, an oncolytic dsRNA virus, modulates human NK cell activity. Reovirus activates NK cells in a type I interferon (IFN‐I) dependent manner, inducing STAT1 and STAT4 signalling in both CD56dim and CD56bright NK cell subsets. Gene expression profiling revealed the dominance of IFN‐I responses and identified induction of genes associated with NK cell cytotoxicity and cell cycle progression, with distinct responses in the CD56dim and CD56bright subsets. However, reovirus treatment inhibited IL‐15 induced NK cell proliferation in an IFN‐I dependent manner and was associated with reduced AKT signalling. In vivo, human CD56dim and CD56bright NK cells responded with similar kinetics to reovirus treatment, but CD56bright NK cells were transiently lost from the peripheral circulation at the peak of the IFN‐I response, suggestive of their redistribution to secondary lymphoid tissue. Coupled with the direct, OV‐mediated killing of tumour cells, the activation of both CD56dim and CD56bright NK cells by antiviral pathways induces a spectrum of activity that includes the NK cell‐mediated killing of tumour cells and modulation of adaptive responses via the trafficking of IFN‐γ expressing CD56bright NK cells to lymph nodes. [ABSTRACT FROM AUTHOR]

High endothelial venules (HEVs) are specialized blood vessels mediating lymphocyte trafficking to lymph nodes (LNs) and other secondary lymphoid organs. By supporting high levels of lymphocyte extravasation from the blood, HEVs play an essential role in lymphocyte recirculation and immune surveillance for foreign invaders (bacterial and viral infections) and alterations in the body's own cells (neoantigens in cancer). The HEV network expands during inflammation in immune-stimulated LNs and is profoundly remodeled in metastatic and tumor-draining LNs. HEV-like blood vessels expressing high levels of the HEV-specific sulfated MECA-79 antigens are induced in non-lymphoid tissues at sites of chronic inflammation in many human inflammatory and allergic diseases, including rheumatoid arthritis, Crohn's disease, allergic rhinitis and asthma. Such vessels are believed to contribute to the amplification and maintenance of chronic inflammation. MECA-79+ tumor-associated HEVs (TA-HEVs) are frequently found in human tumors in CD3+ T cell-rich areas or CD20+ B-cell rich tertiary lymphoid structures (TLSs). TA-HEVs have been proposed to play important roles in lymphocyte entry into tumors, a process essential for successful antitumor immunity and lymphocyte-mediated cancer immunotherapy with immune checkpoint inhibitors, vaccines or adoptive T cell therapy. In this review, we highlight the phenotype and function of HEVs in homeostatic, inflamed and tumor-draining lymph nodes, and those of HEV-like blood vessels in chronic inflammatory diseases. Furthermore, we discuss the role and regulation of TA-HEVs in human cancer and mouse tumor models. [ABSTRACT FROM AUTHOR]

Abstract Background Lymphocytes circulate between peripheral lymphoid tissues via blood and lymphatic systems, and chemokine-induced migration is important in trafficking lymphocytes to distant sites. The small GTPase Rap1 is important in mediating lymphocyte motility, and Rap1-GEFs are involved in chemokine-mediated Rap1 activation. Here, we describe the roles and mechanisms of Rap1-GEFs in lymphocyte trafficking. Results In this study, we show that RA-GEF-1 and 2 (also known as Rapgef2 and 6) are key guanine nucleotide exchange factors (GEF) for Rap1 in lymphocyte trafficking. Mice harboring T cell-specific knockouts of Rapgef2/6 demonstrate defective homing and egress of T cells. Sphingosine-1-phosphate (S1P) as well as chemokines activates Rap1 in a RA-GEF-1/2-dependent manner, and their deficiency in T cells impairs Mst1 phosphorylation, cell polarization, and chemotaxis toward S1P gradient. On the other hand, B cell-specific knockouts of Rapgef2/6 impair chemokine-dependent retention of B cells in the bone marrow and passively facilitate egress. Phospholipase D2-dependent production of phosphatidic acid by these chemotactic factors determines spatial distribution of Rap1-GTP subsequent to membrane localization of RA-GEFs and induces the development of front membrane. On the other hand, basal de-phosphorylation of RA-GEFs is necessary for chemotactic factor-dependent increase in GEF activity for Rap1. Conclusions We demonstrate here that subcellular distribution and activation of RA-GEFs are key factors for a directional movement of lymphocytes and that phosphatidic acid is critical for membrane translocation of RA-GEFs with chemokine stimulation.

Sphingosine 1-phosphate (S1P) plays a role in lymphocyte egress from lymphoid organs. However, it remains unclear how S1P production and secretion are regulated. We show that under inflammatory conditions, α9 integrin, which is closely associated with activated β1 integrin, and its ligand, tenascin-C, colocalize on medullary and cortical sinuses of draining lymph nodes (dLNs), which is a gate for lymphocyte exit, and that inhibition of lymphocyte egress is evident by blockade of α9 integrin-mediated signaling at dLNs. Based on in vitro analysis using lymphatic endothelial cells obtained from mice embryos, we suggested the possibility that stimulation of lymphatic endothelial cells by tenascin-C enhances S1P secretion in an α9 integrin-dependent manner without affecting S1P synthesis and/or degradation. Blockade of α9 integrin-mediated signaling reduced lymphocyte egress from dLNs in several models, including experimental autoimmune encephalomyelitis, where it improved clinical scores and pathology. Therefore, manipulating α9 integrin function may offer a therapeutic strategy for treating various inflammatory disorders.

Tumor-induced remodeling of the microenvironment in lymph nodes (LNs) includes the formation of blood vessels, which goes beyond the regulation of metabolism, and shaping a survival niche for tumor cells. In contrast to solid tumors, which primarily rely on neo-angiogenesis, hematopoietic malignancies usually grow within pre-vascularized autochthonous niches in secondary lymphatic organs or the bone marrow. The mechanisms of vascular remodeling in expanding LNs during infection-induced responses have been studied in more detail; in contrast, insights into the conditions of lymphoma growth and lodging remain enigmatic. Based on previous murine studies and clinical trials in human, we conclude that there is not a universal LN-specific angiogenic program applicable. Instead, signaling pathways that are tightly connected to autochthonous and infiltrating cell types contribute variably to LN vascular expansion. Inflammation related angiogenesis within LNs relies on dendritic cell derived pro-inflammatory cytokines stimulating vascular endothelial growth factor-A (VEGF-A) expression in fibroblastic reticular cells, which in turn triggers vessel growth. In high-grade B cell lymphoma, angiogenesis correlates with poor prognosis. Lymphoma cells immigrate and grow in LNs and provide pro-angiogenic growth factors themselves. In contrast to infectious stimuli that impact on LN vasculature, they do not trigger the typical inflammatory and hypoxia-related stroma-remodeling cascade. Blood vessels in LNs are unique in selective recruitment of lymphocytes via high endothelial venules (HEVs). The dissemination routes of neoplastic lymphocytes are usually disease stage dependent. Early seeding via the blood stream requires the expression of the homeostatic chemokine receptor CCR7 and of L-selectin, both cooperate to facilitate transmigration of tumor and also of protective tumor-reactive lymphocytes via HEV structures. In this view, the HEV route is not only relevant for lymphoma cell homing, but also for a continuous immunosurveillance. We envision that HEV functional and structural alterations during lymphomagenesis are not only key to vascular remodeling, but also impact on tumor cell accessibility when targeted by T cell–mediated immunotherapies. [ABSTRACT FROM AUTHOR]

The STE20-like serine/threonine kinases MST1 and MST2 (MST1/2) are mammalian homologs of Hippo in flies. MST1/2 regulate organ size by suppressing the transcription factor YAP, which promotes proliferation. MST1 is predominantly expressed in immune cells, where it plays distinct roles. Here, we review the functions of MST1/2 in immune cells, uncovered by a series of recent studies, and discuss the connection between MST1/2 function and immune responses. MST1/2 regulate lymphocyte development, trafficking, survival, and antigen recognition by naive T cells. MST1/2 also regulate the function of regulatory T cells and effector T cell differentiation, thus acting to balance immune activation and tolerance. Interestingly, MST1/2 elicit these functions not by the “canonical” Hippo pathway, but by the non-canonical Hippo pathway or alternative pathways. In these pathways, MST1/2 regulates cellular processes relating to immune response, such as chemotaxis, cell adhesion, immunological synapse, gene transcriptions. Recent advances in our understanding of the molecular mechanisms of these processes have revealed important roles of MST1/2 in regulating cytoskeleton remodeling, integrin activation, and vesicular transport in lymphocytes. We discuss the significance of the MST1/2 signaling in lymphocytes in the regulation of organelle dynamics.

Background: Treatment of inflammatory bowel diseases (IBD) has tremendously improved during the last 20 years; however, a substantial fraction of patients does not respond to available therapies or lose response, and new strategies are needed. Summary: Two pharmacological principles have been successfully used for IBD treatment: inhibition of cellular signaling and interference with leukocyte trafficking. Besides tumor necrosis factor, interleukin (IL)-23 is a promising drug target, and antibodies for the combined inhibition of IL-23 and IL-12 (ustekinumab and briakinumab) or selective IL-23 inhibition (brazikumab, risankizumab, and mirikizumab) seem to be effective in Crohn's disease (CD) with emerging evidence also for ulcerative colitis (UC). Janus kinase (JAK) mediates intracellular signaling of a large number of cytokines. Tofacitinib is the first JAK inhibitor approved for UC, and the JAK inhibitors filgotinib and upadacitinib showed potential in CD. Leukocyte trafficking can be inhibited by interference with lymphocyte integrin-α4β7 or endothelial MadCAM-1. The α4β7 integrin inhibitor vedolizumab is an established treatment in IBD, and long-term data of pivotal studies are now available. Additional molecules with therapeutic potential are α4β7-specific abrilumab, β7-specific etrolizumab, and the α4-specific small molecule AJM300. PF-00547659, an antibody against endothelial MadCAM-1, also showed therapeutic potential in UC. Modulation of sphingosine-1-phosphate receptor (S1PR) activity is necessary for the egress of lymphocytes into the circulation, and S1PR modulation results in lymphocyte trapping in lymphatic organs. Ozanimod, an S1PR1 and S1PR5 inhibitor, has been successfully tested in initial studies in UC. Mesenchymal stem cell therapy has been approved for the treatment of complex, active CD fistula, and mesenchymal stem cell therapy might be a paradigm shift for this condition. Autologous stem cell transplantation (ASCT) has been successfully used in CD case series; however, in a randomized trial, a highly stringent endpoint was not met. However, considering positive effects in secondary endpoints, ASCT might be a future treatment of last resort in severe, refractory CD cases, provided that safer protocols can be provided. Key messages: New IBD treatments are successful for a significant fraction of patients. However, new strategies for patient selection, treatment combinations, and/or additional therapies must be developed to serve the need of all IBD patients. [ABSTRACT FROM AUTHOR]

Background: Lymphocytes circulate between peripheral lymphoid tissues via blood and lymphatic systems, and chemokine-induced migration is important in trafficking lymphocytes to distant sites. The small GTPase Rap1 is important in mediating lymphocyte motility, and Rap1-GEFs are involved in chemokine-mediated Rap1 activation. Here, we describe the roles and mechanisms of Rap1-GEFs in lymphocyte trafficking. Results: In this study, we show that RA-GEF-1 and 2 (also known as Rapgef2 and 6) are key guanine nucleotide exchange factors (GEF) for Rap1 in lymphocyte trafficking. Mice harboring T cell-specific knockouts of Rapgef2/6 demonstrate defective homing and egress of T cells. Sphingosine-1-phosphate (S1P) as well as chemokines activates Rap1 in a RA-GEF-1/2-dependent manner, and their deficiency in T cells impairs Mst1 phosphorylation, cell polarization, and chemotaxis toward S1P gradient. On the other hand, B cell-specific knockouts of Rapgef2/6 impair chemokine-dependent retention of B cells in the bone marrow and passively facilitate egress. Phospholipase D2-dependent production of phosphatidic acid by these chemotactic factors determines spatial distribution of Rap1-GTP subsequent to membrane localization of RA-GEFs and induces the development of front membrane. On the other hand, basal de-phosphorylation of RA-GEFs is necessary for chemotactic factor-dependent increase in GEF activity for Rap1. Conclusions: We demonstrate here that subcellular distribution and activation of RA-GEFs are key factors for a directional movement of lymphocytes and that phosphatidic acid is critical for membrane translocation of RA-GEFs with chemokine stimulation. [ABSTRACT FROM AUTHOR]

The STE20-like serine/threonine kinases MST1 and MST2 (MST1/2) are mammalian homologs of Hippo in flies. MST1/2 regulate organ size by suppressing the transcription factor YAP, which promotes proliferation. MST1 is predominantly expressed in immune cells, where it plays distinct roles. Here, we review the functions of MST1/2 in immune cells, uncovered by a series of recent studies, and discuss the connection between MST1/2 function and immune responses. MST1/2 regulate lymphocyte development, trafficking, survival, and antigen recognition by naive T cells. MST1/2 also regulate the function of regulatory T cells and effector T cell differentiation, thus acting to balance immune activation and tolerance. Interestingly, MST1/2 elicit these functions not by the "canonical" Hippo pathway, but by the non-canonical Hippo pathway or alternative pathways. In these pathways, MST1/2 regulates cellular processes relating to immune response, such as chemotaxis, cell adhesion, immunological synapse, gene transcriptions. Recent advances in our understanding of the molecular mechanisms of these processes have revealed important roles of MST1/2 in regulating cytoskeleton remodeling, integrin activation, and vesicular transport in lymphocytes. We discuss the significance of the MST1/2 signaling in lymphocytes in the regulation of organelle dynamics. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease that affects more than 19 million people with incidence increasing rapidly worldwide. For T cells to effectively drive T1D, they must first traffic to the islets and extravasate through the islet vasculature. Understanding the cues that lead to T cell entry into inflamed islets is important because diagnosed T1D patients already have established immune infiltration of their islets. Here we show that CD11c+ cells are a key mediator of T cell trafficking to infiltrated islets in non-obese diabetic (NOD) mice. Using intravital 2-photon islet imaging we show that T cell extravasation into the islets is an extended process, with T cells arresting in the islet vasculature in close proximity to perivascular CD11c+ cells. Antigen is not required for T cell trafficking to infiltrated islets, but T cell chemokine receptor signaling is necessary. Using RNAseq, we show that islet CD11c+ cells express over 20 different chemokines that bind chemokine receptors expressed on islet T cells. One highly expressed chemokine-receptor pair is CXCL16-CXCR6. However, NOD. CXCR6−/− mice progressed normally to T1D and CXCR6 deficient T cells trafficked normally to the islets. Even with CXCR3 and CXCR6 dual deficiency, T cells trafficked to infiltrated islets. These data reinforce that chemokine receptor signaling is highly redundant for T cell trafficking to inflamed islets. Importantly, depletion of CD11c+ cells strongly inhibited T cell trafficking to infiltrated islets of NOD mice. We suggest that targeted depletion of CD11c+ cells associated with the islet vasculature may yield a therapeutic target to inhibit T cell trafficking to inflamed islets to prevent progression of T1D.

Background: Gram-negative infections of the peritoneal cavity result in profound modifications of peritoneal B cell populations and induce the migration of peritoneal B cells to distant secondary lymphoid organs. However, mechanisms controlling the egress of peritoneal B cells from the peritoneal cavity and their subsequent trafficking remain incompletely understood. Sphingosine-1-phosphate (S1P)-mediated signaling controls migratory processes in numerous immune cells. The present work investigates the role of S1P-mediated signaling in peritoneal B cell trafficking under inflammatory conditions. Methods: Differential S1P receptor expression after peritoneal B cell activation was assessed semi‑quantitatively using RT-PCR in vitro. The functional implications of differential S1P1 and S1P4 expression were assessed by transwell migration in vitro, by adoptive peritoneal B cell transfer in a model of sterile lipopolysaccharide (LPS)‑induced peritonitis and in the polymicrobial colon ascendens stent peritonitis (CASP) model. Results: The two sphingosine-1-phosphate receptors (S1PRs) expressed in peritoneal B cell subsets S1P1 and S1P4 are differentially regulated upon stimulation with the TLR4 agonist LPS, but not upon PMA/ionomycin or B cell receptor (BCR) crosslinking. S1P4 deficiency affects both the trafficking of activated peritoneal B cells to secondary lymphoid organs and the positioning of these cells within the functional compartments of the targeted organ. S1P4 deficiency in LPS-activated peritoneal B cells results in significantly reduced numbers of splenic innate response activator B cells. Conclusions: The S1P-S1PR system is implicated in the trafficking of LPS-activated peritoneal B cells. Given the protective role of peritoneal B1a B cells in peritoneal sepsis, further experiments to investigate the impact of S1P4-mediated signaling on the severity and mortality of peritoneal sepsis are warranted.

Type 1 diabetes (T1D) is a T cell mediated autoimmune disease that affects more than 19 million people with incidence increasing rapidly worldwide. For T cells to effectively drive T1D, they must first traffic to the islets and extravasate through the islet vasculature. Understanding the cues that lead to T cell entry into inflamed islets is important because diagnosed T1D patients already have established immune infiltration of their islets. Here we show that CD11c+ cells are a key mediator of T cell trafficking to infiltrated islets in non-obese diabetic (NOD) mice. Using intravital 2-photon islet imaging we show that T cell extravasation into the islets is an extended process, with T cells arresting in the islet vasculature in close proximity to perivascular CD11c+ cells. Antigen is not required for T cell trafficking to infiltrated islets, but T cell chemokine receptor signaling is necessary. Using RNAseq, we show that islet CD11c+ cells express over 20 different chemokines that bind chemokine receptors expressed on islet T cells. One highly expressed chemokine-receptor pair is CXCL16-CXCR6. However, NOD. CXCR6−/− mice progressed normally to T1D and CXCR6 deficient T cells trafficked normally to the islets. Even with CXCR3 and CXCR6 dual deficiency, T cells trafficked to infiltrated islets. These data reinforce that chemokine receptor signaling is highly redundant for T cell trafficking to inflamed islets. Importantly, depletion of CD11c+ cells strongly inhibited T cell trafficking to infiltrated islets of NOD mice. We suggest that targeted depletion of CD11c+ cells associated with the islet vasculature may yield a therapeutic target to inhibit T cell trafficking to inflamed islets to prevent progression of T1D. [ABSTRACT FROM AUTHOR]

Porcine epidemic diarrhea virus (PEDV) is a highly virulent re-emerging enteric coronavirus that causes acute diarrhea, dehydration, and up to 100% mortality in neonatal suckling piglets. Despite this, a safe and effective PEDV vaccine against highly virulent strains is unavailable, making PEDV prevention and control challenging. Lactogenic immunity induced via the gut-mammary gland-secretory IgA (sIgA) axis, remains the most promising and effective way to protect suckling piglets from PEDV. Therefore, a successful PEDV vaccine must induce protective maternal IgA antibodies that passively transfer into colostrum and milk. Identifying variables that influence lymphocyte migration and IgA secretion during gestation and lactation is imperative for designing maternal immunization strategies that generate the highest amount of lactogenic immune protection against PEDV in suckling piglets. Because pregnancy-associated immune alterations influence viral pathogenesis and adaptive immune responses in many different species, a better understanding of host immune responses to PEDV in pregnant swine may translate into improved maternal immunization strategies against enteric pathogens for multiple species. In this review, we discuss the role of host factors during pregnancy on antiviral immunity and their implications for generating protective lactogenic immunity in suckling neonates.

The skin represents a specialized site for immune surveillance consisting of resident, inflammatory and memory populations of lymphocytes. The entry and retention of T cells, B cells, and ILCs is tightly regulated to facilitate detection of pathogens, inflammation and tumors cells. Loss of individual or multiple populations in the skin may break tolerance or increase susceptibility to tumor growth and spread. Studies have significantly advanced our understanding of the role of skin T cells and ILCs at steady state and in inflammatory settings such as viral challenge, atopy, and autoimmune inflammation. The knowledge raised by these studies can benefit to our understanding of immune cell trafficking in primary melanoma, shedding light on the mechanisms of tumor immune surveillance and to improve immunotherapy. This review will focus on the T cells, B cells, and ILCs of the skin at steady state, in inflammatory context and in melanoma. In particular, we will detail the core chemokine and adhesion molecules that regulate cell trafficking to and within the skin, which may provide therapeutic avenues to promote tumor homing for a team of lymphocytes.

The skin represents a specialized site for immune surveillance consisting of resident, inflammatory and memory populations of lymphocytes. The entry and retention of T cells, B cells, and ILCs is tightly regulated to facilitate detection of pathogens, inflammation and tumors cells. Loss of individual or multiple populations in the skin may break tolerance or increase susceptibility to tumor growth and spread. Studies have significantly advanced our understanding of the role of skin T cells and ILCs at steady state and in inflammatory settings such as viral challenge, atopy, and autoimmune inflammation. The knowledge raised by these studies can benefit to our understanding of immune cell trafficking in primary melanoma, shedding light on the mechanisms of tumor immune surveillance and to improve immunotherapy. This review will focus on the T cells, B cells, and ILCs of the skin at steady state, in inflammatory context and in melanoma. In particular, we will detail the core chemokine and adhesion molecules that regulate cell trafficking to and within the skin, which may provide therapeutic avenues to promote tumor homing for a team of lymphocytes. [ABSTRACT FROM AUTHOR]

We investigated the mechanisms by which CD8+ T‐cell trafficking in placenta contributes to perinatal brain injury by studying effects of maternal CD8+ T‐cell depletion (DEP) in a mouse model of intrauterine inflammation (IUI). Maternal CD8+ T cells were depleted with anti‐CD8+ antibodies. IUI was induced with lipopolysaccharide (LPS). DEP was confirmed using flow cytometry. Preterm birth rate was evaluated. Offspring neurologic sequelae were assessed by Nissl staining, immune arrays, confirmatory individual TaqMan® gene assays, and neurobehavioral tests. DEP did not significantly prevent LPS‐induced preterm birth but improved neurobehavioral performance (P < .001) and increased cortical neuronal density (P < .05) in LPS‐exposed pups compared to controls. These changes were associated with decreased CCL3 and CXCL10 and increased CCL5 in DEP LPS‐exposed mice. We demonstrate that DEP reduces perinatal brain injury following IUI. This supports a role for maternal CD8+ T‐cell trafficking in placenta in mediating perinatal brain injury separate from preterm birth mechanisms. [ABSTRACT FROM AUTHOR]

Introduction: Sphingosine-1-phosphate (S1P) regulates the migration of follicular B cells (B2 cells) and directs the positioning of Marginal zone B cells (MZ B cells) within the spleen. The function of S1P signalling in the third B cell lineage, B1 B cells, mainly present in the pleural and peritoneal cavity, has not yet been determined. Methods: S1P receptor expression was analysed in peritoneal B cells by real-time polymerase chain reaction (qPCR). The chemotactic response to S1P was studied in vitro. The role of S1P signalling was further explored in a s1p4−/− mouse strain. Results: Peritoneal B cells expressed considerable amounts of the S1P receptors 1 and 4 (S1P1 and S1P4, respectively). S1P1 showed differential expression between the distinct peritoneal B cell lineages. While B2 cells showed no chemotactic response to S1P, B1 B cells showed a migration response to S1P. s1p4−/− mice displayed significant alterations in the composition of peritoneal B cell populations, as well as a significant reduction of mucosal immunoglobulin A (IgA) in the gut. Discussion: S1P signalling influences peritoneal B1 B cell migration. S1P4 deficiency alters the composition of peritoneal B cell populations and reduces secretory IgA levels. These findings suggest that S1P signalling may be a target to modulate B cell function in inflammatory intestinal pathologies. [ABSTRACT FROM AUTHOR]

Advances in imaging technologies have greatly increased our understanding of cellular and molecular interactions in humans and their corresponding animal models of infectious diseases. In the HIV/SIV field, imaging has provided key insights into mucosal viral transmission, local and systemic virus spread, host-virus dynamics, and chronic inflammation/immune activation and the resultant immunopathology. Recent developments in imaging applications are yielding physical, spatial, and temporal measurements to enhance insight into biological functions and disease processes, while retaining important cellular, microenvironmental, organ, and intact organism contextual details. Taking advantage of the latest advancements in imaging technologies may help answer important questions in the HIV field. The Global HIV Vaccine Enterprise in collaboration with the National Institutes of Health (NIH) sponsored a meeting on May 8 and 9, 2017 to provide a platform to review state-of-the-art imaging technologies and to foster multidisciplinary collaborations in HIV/AIDS research. The meeting covered applications of imaging in studies of early events and pathogenesis, reservoirs, and cure, as well as in vaccine development. In addition, presentations and discussions of imaging applications from non-HIV biomedical research areas were included. This report summarizes the presentations and discussions at the meeting. [ABSTRACT FROM AUTHOR]

Lymphotoxin-beta receptor (LTbR) present on stromal cells engages the noncanonical NF-κB pathway to mediate RelB-dependent expressions of homeostatic chemokines, which direct steady-state ingress of naïve lymphocytes to secondary lymphoid organs (SLOs). In this pathway, NIK promotes partial proteolysis of p100 into p52 that induces nuclear translocation of the RelB NF-jB heterodimers. Microbial infections often deplete homeostatic chemokines; it is thought that infection-inflicted destruction of stromal cells results in the downregulation of these chemokines. Whether inflammation per se also regulates these processes remains unclear. We show that TNF accumulated upon noninfectious immunization of mice similarly downregulates the expressions of these chemokines and consequently diminishes the ingress of naïve lymphocytes in inflamed SLOs. Mechanistically, TNF inactivated NIK in LTbR-stimulated cells and induced the synthesis of Nfkb2 mRNA encoding p100; these together potently accumulated unprocessed p100, which attenuated the RelB activity as inhibitory IjBd. Finally, a lack of p100 alleviated these TNF-mediated inhibitions in inflamed SLOs of immunized Nfkb2-/- mice. In sum, we reveal that an inhibitory TNF-p100 pathway modulates the adaptive compartment during immune responses. [ABSTRACT FROM AUTHOR]

Sphingosine-1-phosphate receptor 1 (S1P1) modulators sequester circulating lymphocytes within lymph nodes, thereby preventing potentially pathogenic autoimmune cells from exiting into the blood stream and reaching inflamed tissues. S1P1 receptor modulation may thus offer potential to treat various autoimmune diseases. The first nonselective S1P1-5 receptor modulator FTY720/fingolimod/Gilenya® has successfully demonstrated clinical efficacy in relapsing forms of multiple sclerosis. However, cardiovascular, hepatic, and respiratory side-effects were reported and there is a need for novel S1P1 receptor modulators with better safety profiles. Here, we describe the discovery of cenerimod, a novel, potent and selective S1P1 receptor modulator with unique S1P1 receptor signaling properties and absence of broncho- and vasoconstrictor effects ex vivo and in vivo. Cenerimod dose-dependently lowered circulating lymphocyte counts in rats and mice after oral administration and effectively attenuated disease parameters in a mouse experimental autoimmune encephalitis (EAE) model. Cenerimod has potential as novel therapy with improved safety profile for autoimmune diseases with high unmet medical need. [ABSTRACT FROM AUTHOR]

Idiopathic pneumonia syndrome (IPS) is a noninfectious inflammatory disorder of the lungs that occurs most often after fully myeloablative allogeneic hematopoietic stem cell transplantation (HSCT). IPS can be severe and is associated with high 1-year mortality rates despite existing therapies. The canonical nuclear factor-(NF) κB signaling pathway has previously been linked to several inflammatory disorders of the lung, including asthma and lung allograft rejection. It has never been specifically targeted as a novel IPS treatment approach, however. Here, we report that the IκB kinase 2 (IKK2) antagonist BAY 65-5811 or “compound A,” a highly potent and specific inhibitor of the NF-κB pathway, was able to improve median survival times and recipient oxygenation in a well-described mouse model of IPS. Compound A impaired the production of the proinflammatory chemokines CCL2 and CCL5 within the host lung after transplantation. This resulted in significantly lower numbers of donor lung infiltrating CD4 + and CD8 + T cells and reduced pulmonary inflammatory cytokine production after allograft. Compound A's beneficial effects appeared to be specific for limiting pulmonary injury, as the drug was unable to improve outcomes in a B6 into B6D2 haplotype-matched murine HSCT model in which recipient mice succumb to lethal acute graft-versus-host disease of the gastrointestinal tract. Collectively, our data suggest that the targeting of the canonical NF-κB pathway with a small molecule IKK2 antagonist may represent an effective and novel therapy for the specific management of acute lung injury that can occur after allogeneic HSCT. [ABSTRACT FROM AUTHOR]

The nervous and immune systems are the principal organ systems that sense internal and external environments, and evoke adaptive responses to maintain homeostasis. Studies in the past few decades discovered commonalities between the two organ systems. They share many functional molecules and respond to various stimuli with high specificity. Additionally, it has long been suggested that there is also cross-talk between the nervous and immune systems. However, the cellular and molecular basis for neuroimmune interactions has emerged only in the past decade. Adrenergic nerves constitute the efferent arc of the sympathetic nervous system and coordinate organ functions in the entire body. Recently, studies have shown that adrenergic nerves regulate the trafficking of myeloid and lymphoid immune cells through distinct molecular mechanisms. In the present review, we focus on the role of adrenergic nerves in the control of lymphocyte trafficking and adaptive immune responses in physiological and pathological conditions. [ABSTRACT FROM AUTHOR]

Summary The interaction between oxysterols and the G protein-coupled receptor Epstein-Barr virus-induced gene 2 (EBI2) fine-tunes immune cell migration, a mechanism efficiently targeted by several disease-modifying treatments developed to treat multiple sclerosis (MS), such as natalizumab. We previously showed that memory CD4 + T lymphocytes migrate specifically in response to 7α,25-dihydroxycholesterol (7α,25-OHC) via EBI2 in the MS murine model experimental autoimmune encephalomyelitis. However, the EBI2 expression profile in human lymphocytes in both healthy and MS donors is unknown. Here, we characterize EBI2 biology in human lymphocytes. We observed that EBI2 is functionally expressed on memory CD4 + T cells and is enhanced under natalizumab treatment. These data suggest a significant role for EBI2 in human CD4 + T cell migration, notably in patients with MS. Better knowledge of EBI2 involvement in autoimmunity may therefore lead to an improved understanding of the physiopathology of MS. [ABSTRACT FROM AUTHOR]

B cells play a central role in multiple sclerosis (MS) pathology. B and plasma cells may contribute to disease activity through multiple mechanisms: antigen presentation, cytokine secretion, or antibody production. Molecular analyses of B cell populations in MS patients have revealed significant overlaps between peripheral lymphoid and clonally expanded central nervous system (CNS) B cell populations indicating that B cell trafficking may play a critical role in driving MS exacerbations. In this review, we will assess our current knowledge of the mechanisms and pathways governing B cell migration into the CNS and examine evidence for and against a compartmentalized B cell response driving progressive MS pathology.

Introduction: Sphingosine-1-phosphate (S1P) regulates the migration of follicular B cells (B2 cells) and directs the positioning of Marginal zone B cells (MZ B cells) within the spleen. The function of S1P signalling in the third B cell lineage, B1 B cells, mainly present in the pleural and peritoneal cavity, has not yet been determined. Methods: S1P receptor expression was analysed in peritoneal B cells by real-time polymerase chain reaction (qPCR). The chemotactic response to S1P was studied in vitro. The role of S1P signalling was further explored in a s1p4−/− mouse strain. Results: Peritoneal B cells expressed considerable amounts of the S1P receptors 1 and 4 (S1P1 and S1P4, respectively). S1P1 showed differential expression between the distinct peritoneal B cell lineages. While B2 cells showed no chemotactic response to S1P, B1 B cells showed a migration response to S1P. s1p4−/− mice displayed significant alterations in the composition of peritoneal B cell populations, as well as a significant reduction of mucosal immunoglobulin A (IgA) in the gut. Discussion: S1P signalling influences peritoneal B1 B cell migration. S1P4 deficiency alters the composition of peritoneal B cell populations and reduces secretory IgA levels. These findings suggest that S1P signalling may be a target to modulate B cell function in inflammatory intestinal pathologies.

Sphingosine 1-phosphate (S1P) is a sphingosine containing lipid intermediate obtained from ceramide. S1P is known to be an important signaling molecule and plays multiple roles in the context of immunity. This lysophospholipid binds and activates G-protein-coupled receptors (GPCRs) known as S1P receptors 1–5 (S1P1–5). Once activated, these GPCRs mediate signaling that can lead to alterations in cell proliferation, survival or migration, and can also have other effects such as promoting angiogenesis. In this review, we will present evidence demonstrating a role for S1P in lymphocyte migration, inflammation and infection, as well as in cancer. The therapeutic potential of targeting S1P receptors, kinases and lyase will also be discussed. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a progressive autoimmune disease of the CNS with its underlying mechanisms not fully understood. In the present study, we tested the hypothesis that caveolin-1, a major membrane scaffolding protein, plays a critical role in the pathogenesis of experimental autoimmune encephalomyelitis, a laboratory murine model of MS. We found increased expression of caveolin-1 in serum and spinal cord tissues in association with disease incidence and severity in wild-type mice with active encephalomyelitis. After immunization, Cav-1 knock-out mice showed remarkable disease resistance with decreased incidence and clinical symptoms. Furthermore, Cav-1 knock-out mice had alleviated encephalitogenic T cells trafficking into the CNS with decreased expressions of adhesion molecules ICAM-1 and VCAM-1 within the lesions. In agreement with in vivo studies, in vitro knockdown of caveolin-1 compromised the upregulation of ICAM-1 in endothelial cells, leading to the amelioration of the transendothelial migration of pathogenic TH1 and TH17 cells. Together, those results indicate that caveolin-1 serves as an active modulator of CNS-directed lymphocyte trafficking and could be a therapeutic target for neuroinflammatory diseases, such as multiple sclerosis. [ABSTRACT FROM AUTHOR]

During nasal immune responses, lymphocytes activated in the nasopharynx-associated lymphoid tissue (NALT) are thought to traffic to the nasal mucosa. Here we found a prominent infiltration of CD4 + memory T cells into the nasal mucosa in a mouse model of allergic rhinitis. CCR3 and CCR10 mRNA was increased in the NALT, and CCR3- or CCR10-expressing CD4 + T cells were present in the nasal mucosa. CCL28, a chemokine ligand for CCR3 and CCR10, was upregulated in nasal epithelial cells. Our results suggest that memory CD4 + T cells traffic to the nasal mucosa in a process that may involve CCL28 and its receptors CCR3 and CCR10. [ABSTRACT FROM AUTHOR]

Staging of oral squamous cell carcinoma is based on the tumour-node-metastasis (TNM) system, which has been deemed insufficient for prognostic purposes. Hence, better prognostic tools are needed to reflect the biological diversity of these cancers. Previously, high numbers of specialized blood vessels called high-endothelial venules have been reported to be associated with prolonged survival in patients with breast cancer. In this study, we analysed the prognostic value and morphological characteristics of tumour-associated high-endothelial venules in oral cancer. The presence of tumour-associated high-endothelial venules was evaluated by immunohistochemistry in 75 patients with oral squamous cell carcinoma and analysed with correlation to clinicopathological parameters, patients' survival and vessel morphology. Ten of the samples were analysed at multiple levels to evaluate intratumoural heterogeneity. The presence of tumour-associated high-endothelial venules was found to be associated with lower disease-specific death in multivariate regression analyses ( P = 0.002). High-endothelial venules were present in all ( n = 53) T1-T2 tumours, but only in two thirds ( n = 14) of the T3-T4 tumours. The morphology of high-endothelial venules was heterogeneous and correlated with lymphocyte density. High-endothelial venules were found to be distributed homogeneously within the tumours. We found the presence of tumour-associated high-endothelial venules to be an easy-to-use, robust, and independent positive prognostic factor for patients with oral cancer. Absence of these vessels in advanced-stage tumours might identify patients with more aggressive disease. Evaluating the presence of tumour-associated high-endothelial venules might help to tailor the treatment of oral cancer patients to their individual needs. [ABSTRACT FROM AUTHOR]

Peritoneal B-1a cells are characterized by their expression of CD5 and enrichment for germline-encoded IgM B cell receptors. Early studies showing expression of a diverse array of VDJ sequences among purified B-1a cells provided a molecular basis for understanding the heterogeneity of the B-1a cell repertoire. Antigen-driven positive selection and the identification of B-1a specific progenitors suggest multiple origins of B-1a cells. The introduction of new markers such as PD-L2, CD25, CD73, and PC1 (plasma cell alloantigen 1, also known as ectonucleotide phosphodiesterase/pyrophosphatase 1) further helped to identify phenotypically and functionally distinct B-1a subsets. Among many B-1a subsets defined by these new markers, PC1 is unique in that it subdivides B-1a cells into PC1hi and PC1lo subpopulations with distinct functions, such as production of natural IgM and gut IgA, response to the pneumococcal antigen PPS-3, secretion of interleukin-10, and support for T helper 1 (TH1) cell differentiation. RNA sequencing of these subsets revealed differential expression of genes involved in cellular movement and immune cell trafficking. We will discuss these new insights underlying the heterogeneous nature of the B-1a cell repertoire. [ABSTRACT FROM AUTHOR]

B cells play a central role in multiple sclerosis (MS) pathology. B and plasma cells may contribute to disease activity through multiple mechanisms: antigen presentation, cytokine secretion, or antibody production. Molecular analyses of B cell populations in MS patients have revealed significant overlaps between peripheral lymphoid and clonally expanded central nervous system (CNS) B cell populations, indicating that B cell trafficking may play a critical role in driving MS exacerbations. In this review, we will assess our current knowledge of the mechanisms and pathways governing B cell migration into the CNS and examine evidence for and against a compartmentalized B cell response driving progressive MS pathology. [ABSTRACT FROM AUTHOR]

[Display omitted] • CAR-T cell therapies exhibit distinct cellular kinetic profiles that influence clinical outcomes. • CAR-T cellular kinetics are less favorable in solid tumor settings. • Mathematical modeling methods are commonly applied to assess, characterize, and predict the cellular kinetics of CAR-T cells and their relationship to tumor killing. • The clonal heterogeneity of CAR-T cell therapies may confound direct linking of cellular kinetics to efficacy. To the extent that pharmacokinetics influence the effectiveness of nonliving therapeutics, so too do cellular kinetics influence the efficacy of Chimeric Antigen Receptor (CAR) -T cell therapy. Like conventional therapeutics, CAR-T cell therapies undergo a distribution phase upon administration. Unlike other therapeutics, however, this distribution phase is followed by subsequent phases of expansion, contraction, and persistence. The magnitude and duration of these phases unequivocally influence clinical outcomes. Furthermore, the "pharmacodynamics" of CAR-T cells is truly dynamic, as cells can rapidly become exhausted and lose their therapeutic efficacy. Mathematical models are among the translational tools commonly applied to assess, characterize, and predict the complex cellular kinetics and dynamics of CAR-T cells. Here, we provide a focused review of the cellular kinetics of CAR-T cells, the mechanisms underpinning their complexity, and the mathematical modeling approaches used to interrogate them. [ABSTRACT FROM AUTHOR]