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Objectives Recent transcriptome analyses revealed that 15-fold expanded HLA-DR+ CD90+ synovial fibroblasts (SFs) are potential key mediators of inflammation in rheumatoid arthritis (RA). The reasons for the expansion of HLA-DR+ CD90+ SFs are unclear, but genetic signatures indicated a central role of IFNɣ in the generation of this fibroblast subset. In the present study, we investigated the generation of HLA-DR+ CD90+ SFs and their function. We hypothesized that infiltrating leukocytes such as NK cells become activated in situ, provide IFNɣ and thus contribute to the generation of arthritic HLA-DR+ CD90+ SFs. Methods We combined functional assays using primary human materials and focused bioinformatic analyses of mass cytometry and transcriptomics patient datasets. Results We detected enriched and activated FcɣRIIIA(CD16)+ NK cells in synovia from active RA. CD16 recognized immune complexes in synovial fluid, potentially contributing to NK cell activation in RA. In vitro, NK cell-derived IFNɣ induced HLA-DR and an inflammatory, cytokine secreting, HLA-DR+ phenotype in CD90+ SFs. HLA-DR+ CD90+ SFs consecutively activated CD4+ T cells upon receptor crosslinking via superantigens. HLA-DR+ CD90+ SFs also activated CD4+ T cells in absence of superantigens, an effect that was boosted by NK cell-derived IFNɣ and that was four times stronger in RA compared to osteoarthritis. Finally, JAK inhibition prevented HLA-DR induction and blocked pro-inflammatory signals to T cells. Conclusions HLA-DR+ CD90+ SFs are an activation state that can be induced by IFNɣ, likely provided from infiltrating leukocytes such as activated NK cells. The induction of these pro-inflammatory, IL-6 producing and likely antigen-presenting SFs can be targeted by JAK inhibition.

The integrin LFA-1 is crucial for T-cell/ APC interactions and sensitive recognition of antigens. Precise nanoscale organization and valency regulation of LFA-1 are mandatory for an appropriate function of the immune system. While the inside-out signals regulating the LFA-1 affinity are well described, the molecular mechanisms controlling LFA-1 avidity are still not fully understood. Here, we show that activation of the actin-bundling protein L-plastin (LPL) through phosphorylation at serine-5 enables the formation of clusters containing LFA-1 in high-affinity conformation. Phosphorylation of LPL is induced by an nPKC-MEK-p90RSK pathway and counter-regulated by the serine-threonine phosphatase PP2A. Interestingly, recruitment of LFA-1 into the T-cell/APC contact zone is not affected by LPL phosphorylation. Instead, for this process, activation of the actin-remodeling protein cofilin through dephosphorylation is essential. Together, this study reveals a dichotomic spatial regulation of LFA-1 clustering and microscale movement in T-cells by two different actin-binding proteins, LPL and cofilin.

The number and activity of T cell subsets in the atherosclerotic plaques are critical for the prognosis of patients with acute coronary syndrome. β2 Integrin activation is pivotal for T cell recruitment and correlates with future cardiac events. Despite this knowledge, differential regulation of adhesiveness in T cell subsets has not been explored yet. In this study, we show that in human T cells, SDF-1α–mediated β2 integrin activation is driven by a, so far, not-described reactive oxidative species (ROS)–regulated calcium influx. Furthermore, we show that CD4+CD28null T cells represent a highly reactive subset showing 25-fold stronger β2 integrin activation upon SDF-1α stimulation compared with CD28+ T cells. Interestingly, ROS-dependent Ca release was much more prevalent in the pathogenetically pivotal CD28null subset compared with the CD28+ T cells, whereas the established mediators of the classical pathways for β2 integrin activation (PKC, PI3K, and PLC) were similarly activated in both T cell subsets. Thus, interference with the calcium flux attenuates spontaneous adhesion of CD28null T cells from acute coronary syndrome patients, and calcium ionophores abolished the observed differences in the adhesion properties between CD28+ and CD28null T cells. Likewise, the adhesion of these T cell subsets was indistinguishable in the presence of exogenous ROS/H2O2. Together, these data provide a molecular explanation of the role of ROS in pathogenesis of plaque destabilization.

ObjectivesNeutrophils are typically the most abundant leukocyte in arthritic synovial fluid. We sought to understand changes that occur in neutrophils as they migrate from blood to joint.MethodsWe performed RNA sequencing of neutrophils from healthy human blood, arthritic blood, and arthritic synovial fluid, comparing transcriptional signatures with those from murine K/BxN serum transfer arthritis. We employed mass cytometry to quantify protein expression and sought to reproduce the synovial fluid phenotypeex vivoin cultured healthy blood neutrophils.ResultsBlood neutrophils from healthy donors and patients with active arthritis exhibited largely similar transcriptional signatures. By contrast, synovial fluid neutrophils exhibited more than 1,600 differentially expressed genes. Gene signatures identified a prominent response to interferon gamma (IFNγ), as well as to tumor necrosis factor, interleukin 6, and hypoxia, in both humans and mice. Mass cytometry also found healthy and arthritic donor blood neutrophils largely indistinguishable but revealed a range of neutrophil phenotypes in synovial fluid defined by downregulation of CXCR1 and upregulation of FcγRI, HLA-DR, PD-L1, ICAM-1 and CXCR4. Reproduction of key elements of this signature in cultured blood neutrophils required both IFNγ and prolonged culture.ConclusionsCirculating neutrophils from arthritis patients resemble those from healthy controls, but joint fluid cells exhibit a network of changes, conserved across species, that implicate IFNγ response and aging as complementary drivers of the synovial neutrophil phenotype.KEY MESSAGESWhat is already known about this subject?Neutrophils are central in the effector phase of inflammatory arthritis but their phenotypic heterogeneity in inflamed synovial fluid is poorly understood.What does this study add?RNA-seq and mass cytometry identify a hallmark phenotype of neutrophils in synovial fluid consisting of upregulated ICAM-1, HLA-DR, PD-L1, Fc receptors and CXCR4.Transcriptomics highlight an IFNγ response signature conserved across humans and mice.In vitro experiments implicate aging and IFNγ as complementary factors orchestrating the synovial fluid neutrophil phenotype.How might this impact on clinical practice or future developments?Understanding the specific features of neutrophils in the arthritic joint may disclose opportunities for safe therapeutic targeting of this lineage.

The interplay between keratinocytes and immune cells, especially T cells, plays an important role in the pathogenesis of chronic inflammatory skin diseases. During psoriasis, keratinocytes attract T cells by releasing chemokines, while skin-infiltrating self-reactive T cells secrete proinflammatory cytokines, e.g., IFNγ and IL-17A, that cause epidermal hyperplasia. Similarly, in chronic graft-versus-host disease, allogenic IFNγ-producing Th1/Tc1 and IL-17-producing Th17/Tc17 cells are recruited by keratinocyte-derived chemokines and accumulate in the skin. However, whether keratinocytes act as nonprofessional antigen-presenting cells to directly activate naive human T cells in the epidermis remains unknown. Here, we demonstrate that under proinflammatory conditions, primary human keratinocytes indeed activate naive human T cells. This activation required cell contact and costimulatory signaling via CD58/CD2 and CD54/LFA-1. Naive T cells costimulated by keratinocytes selectively differentiated into Th1 and Th17 cells. In particular, keratinocyte-initiated Th1 differentiation was dependent on costimulation through CD58/CD2. The latter molecule initiated STAT1 signaling and IFNγ production in T cells. Costimulation of T cells by keratinocytes resulting in Th1 and Th17 differentiation represents a new explanation for the local enrichment of Th1 and Th17 cells in the skin of patients with a chronic inflammatory skin disease. Consequently, local interference with T cell–keratinocyte interactions may represent a novel strategy for the treatment of Th1 and Th17 cell-driven skin diseases.

Cytokines released during chronic inflammatory diseases induce pro-inflammatory properties in polymorphonuclear neutrophils (PMN). Here we show that in vitro cytokine treatment leads to the development of a subgroup of human PMN expressing CCR5, termed CCR5+ cytokine-induced PMN (CCR5+ cPMN). Auto/paracrine TNF signaling increases intracellular neutrophil elastase (ELANE) abundance and induces NETosis in CCR5+ cPMN. Triggering of CCR5 amplifies NETosis. Membranous TNF (mTNF) outside-in signaling induces the formation of reactive oxygen species, a known activator of NETosis. In vivo, we find an increased number of CCR5+ cPMN in the peripheral blood and inflamed lamina propria of patients with ulcerative colitis (UC) but not Crohn’s disease (CD). Notably, failure of anti-TNF therapy is associated with higher frequencies of CCR5+ cPMN. In conclusion, we identify a phenotype of pro-NETotic, CCR5 positive PMN present in inflamed tissue in vivo and inducible in vitro. These cells may reflect an important component of tissue damage during chronic inflammation and could be of diagnostic value.

The understanding of the tumor microenvironment (TME) has been expanding in recent years in the context of interactions among different cell types, through direct cell–cell communication as well as through soluble factors. It has become evident that the development of a successful antitumor response depends on several TME factors. In this context, the number, type, and subsets of immune cells, as well as the functionality, memory, and exhaustion state of leukocytes are key factors of the TME. Both the presence and functionality of immune cells, in particular T cells, are regulated by cellular and soluble factors of the TME. In this regard, one fundamental reason for failure of antitumor responses is hijacked immune cells, which contribute to the immunosuppressive TME in multiple ways. Specifically, reactive oxygen species (ROS), metabolites, and anti-inflammatory cytokines have central roles in generating an immunosuppressive TME. In this review, we focused on recent developments in the immune cell constituents of the TME, and the micromilieu control of antitumor responses. Furthermore, we highlighted the current challenges of T cell-based immunotherapies and potential future strategies to consider for strengthening their effectiveness.

The integrin LFA-1 is crucial for T-cell/ APC interactions and sensitive recognition of antigens. Precise nanoscale organization and valency regulation of LFA-1 are mandatory for an appropriate function of the immune system. While the inside-out signals regulating the LFA-1 affinity are well described, the molecular mechanisms controlling LFA-1 avidity are still not fully understood. Here, we show that activation of the actin-bundling protein L-plastin (LPL) through phosphorylation at serine-5 enables the formation of clusters containing LFA-1 in high-affinity conformation. Phosphorylation of LPL is induced by an nPKC-MEK-p90

NF-κB inducing kinase (NIK) is the key protein of the non-canonical NF-κB pathway and is important for the development of lymph nodes and other secondary immune organs. We elucidated the specific role of NIK in T cells using T-cell specific NIK-deficient (NIKΔT) mice. Despite showing normal development of lymphoid organs, NIKΔT mice were resistant to induction of CNS autoimmunity. T cells from NIKΔT mice were deficient in late priming, failed to up-regulate T-bet and to transmigrate into the CNS. Proteomic analysis of activated NIK-/- T cells showed de-regulated expression of proteins involved in the formation of the immunological synapse: in particular, proteins involved in cytoskeleton dynamics. In line with this we found that NIK-deficient T cells were hampered in phosphorylation of Zap70, LAT, AKT, ERK1/2 and PLCγ upon TCR engagement. Hence, our data disclose a hitherto unknown function of NIK in T-cell priming and differentiation.

The clearance of tumors or virus infected cells is a crucial task of the immune system. Cytotoxic T-cells (CTLs) are able to detect and to kill such altered host cells. Given the recent success of checkpoint inhibitors for tumor therapy, it becomes more and more important to understand the biology of T-cell mediated target cell killing. Tests that allow analyzing the biology of CTLs are either based on flow cytometry or fluorescence microscopy. Thus, they either lack image-based information or have a poor statistical robustness. Therefore, we describe an approach to quantify CTL-mediated cytotoxicity using imaging flow cytometry. Using activated primary human cytotoxic T-cells as CTLs and P815 as target cells, we show that both the evaluation of target cell death and the biology of CTLs can be evaluated in parallel. This enables to gain information about CTL-mediated cytotoxicity in samples from patients important for translational medicine. J. Cell. Biochem. 118: 2528-2533, 2017. © 2017 Wiley Periodicals, Inc.

Neutrophils or polymorphonuclear cells (PMN) eliminate bacteria via phagocytosis and/or NETosis. Apart from these conventional roles, PMN also have immune-regulatory functions. They can transdifferentiate and upregulate MHCII as well as ligands for costimulatory receptors which enables them to behave as antigen presenting cells (APC). The initial step for activating T-cells is the formation of an immune synapse between T-cells and antigen-presenting cells. However, the immune synapse that develops at the PMN/T-cell contact zone is as yet hardly investigated due to the non-availability of methods for analysis of large number of PMN interactions. In order to overcome these obstacles, we introduce here a workflow to analyse the immune synapse of primary human PMN and T-cells using multispectral imaging flow cytometry (InFlow microscopy) and super-resolution microscopy. For that purpose, we used CD3 and CD66b as the lineage markers for T-cells and PMN, respectively. Thereafter, we applied and critically discussed various "masks" for identification of T-cell PMN interactions. Using this approach, we found that a small fraction of transdifferentiated PMN (CD66b+CD86high) formed stable PMN/T-cell conjugates. Interestingly, while both CD3 and CD66b accumulation in the immune synapse was dependent on the maturation state of the PMN, only CD3 accumulation was greatly enhanced by the presence of superantigen. The actin cytoskeleton was weakly rearranged at the PMN side on the immune synapse upon contact with a T-cell in the presence of superantigen. A more detailed analysis using super-resolution microscopy (structured-illumination microscopy, SIM) confirmed this finding. Together, we present an InFlow microscopy based approach for the large scale analysis of PMN/T-cell interactions and - combined with SIM - a possibility for an in-depth analysis of protein translocation at the site of interactions.

T-cells need to be tightly regulated during their activation and effector phase to assure an appropriate defence against cancer or pathogens and - vice versa - to avoid autoimmune reactions. Regulatory signals are provided via the immune synapse between T-cells and antigen-presenting cells (APCs) or target cells. The stability and kinetics of immune synapse formation is critical for proper T-cell functions. It requires dynamic rearrangements of the actin cytoskeleton necessary for organized spatio-temporal redistribution of receptors and adhesion molecules. We identified glucocorticoid-sensitive phosphorylation of serine 5 on the actin-bundling protein L-plastin as one important signalling event for this regulation. Using imaging flow cytometry as well as confocal and super-resolution microscopy we showed that L-plastin relocalizes to the immune synapse upon antigen encounter, where it associates with the β2-subunit of LFA-1 (CD11a/CD18). Interfering with L-plastin expression or activation leads to a defective LFA-1 recruitment and unstable T-cell/APC contacts. Consequently, the lack of L-plastin diminishes T-cell activation, proliferation and proximal effector responses such as cytokine production. On the other hand, a pro-oxidative milieu leads to prolonged activation of L-plastin resulting in a stronger enrichment of LFA-1 in the cytolytic immune synapse. Concomitant stabilization of conjugates formed by cytotoxic T-cells (CTLs) and their target cells impairs the ability of CTLs to kill more than one target cells (serial killing), which de facto leads to a downregulation of T-cell cytotoxicity. Together, we demonstrate that activation and spacial distribution of L-plastin regulates the maturation and stability of activating and cytolytic immune synapses important for T-cell activation and effector functions.

Background The enteric nervous system (ENS), a complex network of neurons and glial cells, coordinates major gastrointestinal functions. Impaired development or secondary aberrations cause severe enteric neuropathies. Neural crest-derived stem cells as well as enteric neuronal progenitor cells, which form enteric neurospheres, represent a promising tool to unravel molecular pathomechanisms and to develop novel therapy options. However, so far little is known about the detailed cellular composition and the proportional distribution of enteric neurospheres. Comprehensive knowledge will not only be essential for basic research but also for prospective cell replacement therapies to restore or to improve enteric neuronal dysfunction. Methods Human enteric neurospheres were generated from three individuals with varying age. For detailed molecular characterization, nCounter target gene expression analyses focusing on stem, progenitor, neuronal, glial, muscular, and epithelial cell markers were performed. Corresponding archived paraffin-embedded individuals' specimens were analyzed accordingly. Key results Our data revealed a remarkable molecular complexity of enteric neurospheres and archived specimens. Amongst the expression of multipotent stem cell, progenitor cell, neuronal, glial, muscle and epithelial cell markers, moderate levels for the pluripotency marker POU5F1 were observed. Furthermore, besides the interindividual variability, we identified highly distinct intraindividual expression profiles. Conclusions & inferences Our results emphasize the assessment of molecular signatures to be essential for standardized use, optimization of experimental approaches, and elimination of potential risk factors, as the formation of tumors. Our study pipeline may serve as a blueprint implemented into the characterization procedure of enteric neurospheres for various future applications.

The immune synapse is the area of communication between T cells and antigen-presenting cells (APCs). T cells polarize surface receptors and proteins towards the immune synapse to assure a stable binding and signal exchange. Classical confocal, TIRF, or super-resolution microscopy have been used to study the immune synapse. Since these methods require manual image acquisition and time-consuming quantification, the imaging of rare events is challenging. Here, we describe a workflow that enables the morphological analysis of tens of thousands of cells. Immune synapses are induced between primary human T cells in pan-leukocyte preparations and Staphylococcus aureus enterotoxin B (SEB)-loaded Raji cells as APCs. Image acquisition is performed with imaging flow cytometry, also called In-Flow microscopy, which combines features of a flow cytometer and a fluorescence microscope. A complete gating strategy for identifying T cell/APC couples and analyzing the immune synapses is provided. As this workflow allows the analysis of immune synapses in unpurified pan-leukocyte preparations and hence requires only a small volume of blood (i.e., 1 mL), it can be applied to samples from patients. Importantly, several samples can be prepared, measured, and analyzed in parallel.

Patients with the neurological disorder HSAN-I suffer frequent infections, attributed to a lack of pain sensation and failure to seek care for minor injuries. Whether protective CD8(+) T cells are affected in HSAN-I patients remains unknown. Here, we report that HSAN-I-associated mutations in serine palmitoyltransferase subunit SPTLC2 dampened human T cell responses. Antigen stimulation and inflammation induced SPTLC2 expression, and murine T-cell-specific ablation of Sptlc2 impaired antiviralT-cell expansion and effector function. Sptlc2 deficiency reduced sphingolipid biosynthetic flux and led to prolonged activation of the mechanistic target of rapamycin complex 1 (mTORC1), endoplasmic reticulum (ER) stress, and CD8(+) T cell death. Protective CD8(+) T cell responses in HSAN-I patient PBMCs and Sptlc2-deficient mice were restored by supplementing with sphingolipids and pharmacologically inhibiting ER stress-induced cell death. Therefore, SPTLC2 underpins protective immunity by translating extracellular stimuli into intracellular anabolic signals and antagonizes ER stress to promote T cell metabolic fitness.

// Matthias M. Gaida 1 , Christine Mayer 2 , Ulrike Dapunt 3 , Sabine Stegmaier 4 , Peter Schirmacher 1 , Guido H. Wabnitz 4 and G. Maria Hansch 4 1 Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany 2 Department for Gynecology and Obstetrics, University Hospital Heidelberg, Heidelberg, Germany 3 Department for Orthopedics, University Hospital Heidelberg, Heidelberg, Germany 4 Institute of Immunology, University Heidelberg, Heidelberg, Germany Correspondence to: Matthias M. Gaida, email: // Keywords : pancreatic cancer, bitter receptor, microbiome, ABCB1 Received : October 10, 2015 Accepted : January 24, 2016 Published : February 05, 2016 Abstract T2R38 belongs to the family of bitter receptors and was initially detected in cells of the oral cavity. We now describe expression of T2R38 in tumor cells in patients with pancreatic cancer and in tumor-derived cell lines. T2R38 is localized predominantly intracellular in association with lipid droplets, particularly with the lipid droplet membrane. The receptor can be activated by the bona fide ligand for T2R38, phenylthiourea (PTU), and by N-acetyl-dodecanoyl homoserine (AHL-12), a quorum sensing molecule of Pseudomonas aeruginosa , the latter is the only known natural ligand for T2R38. In response to PTU or AHL-12, key transcription factors are activated including phosphorylation of the MAP kinases p38 and ERK1/2, and upregulation of NFATc1. Moreover, we found increased expression of the multi-drug resistance protein 1 (also known as ABCB1), a transmembrane transporter molecule, participating in shuttling of a plethora of drugs, such as chemotherapeutics or antibiotics. In conclusion, our data indicate a new, additional function of the taste receptor T2R38 beyond sensing “bitter”. Moreover, because T2R38 can be stimulated by a bacteria-derived signaling molecule the receptor could link microbiota and cancer.

While several protein serine/threonine kinases control cytokine production by T cells, the roles of serine/threonine phosphatases are largely unexplored. Here, we analyzed the involvement of protein phosphatase 1α (PP1α) in cytokine synthesis following costimulation of primary human T cells. Small interfering RNA (siRNA)-mediated knockdown of PP1α (PP1(KD)) or expression of a dominant negative PP1α (D95N-PP1) drastically diminished interleukin-10 (IL-10) production. Focusing on a key transcriptional activator of human IL-10, we demonstrate that nuclear translocation of NF-κB was significantly inhibited in PP1(KD) or D95N-PP1 cells. Interestingly, knockdown of cofilin, a known substrate of PP1 containing a nuclear localization signal, also prevented nuclear accumulation of NF-κB. Expression of a constitutively active nonphosphorylatable S3A-cofilin in D95N-PP1 cells restored nuclear translocation of NF-κB and IL-10 expression. Subpopulation analysis revealed that defective nuclear translocation of NF-κB was most prominent in CD4(+) CD45RA(−) CXCR3(−) T cells that included IL-10-producing T(H)2 cells. Together these findings reveal novel functions for PP1α and its substrate cofilin in T cells namely the regulation of the nuclear translocation of NF-κB and promotion of IL-10 production. These data suggest that stimulation of PP1α could limit the overwhelming immune responses seen in chronic inflammatory diseases.

Abdominal aortic aneurysm (AAA) is heavily infiltrated with leukocytes, expressing the DNA sensor absent in melanoma 2 (AIM2) and other inflammasome components. Using multicolour flow cytometry, we here compared the expression of the inflammasome components AIM2, NLRP3, and ASC in different peripheral immune cells derived from AAA patients with those from non-AAA patients in a case–control study. In parallel, peripheral blood mononuclear cells (PBMC) of AAA patients and controls were stimulated in vitro with poly-dA:dT or lipopolysaccharide (LPS) to analyze inflammasome activation. AIM2 expression was significantly increased in peripheral granulocytes (P = 0.026), monocytes (P = 0.007), B lymphocytes (P

Plasma fibronectin is a circulating protein that facilitates phagocytosis by connecting bacteria to immune cells. A fibronectin isoform, which includes a sequence of 90 AA called extra-domain B (EDB), is synthesized de novo at the messenger RNA (mRNA) level in immune cells, but the reason for its expression remains elusive. We detected an 80-fold increase in EDB-containing fibronectin in the cerebrospinal fluid of patients with bacterial meningitis that was most pronounced in staphylococcal infections. A role for this isoform in phagocytosis was further suggested by enhanced EDB fibronectin release after internalization of Staphylococcus aureus in vitro. Using transgenic mouse models, we established that immune cell production of fibronectin contributes to phagocytosis, more so than circulating plasma fibronectin, and that accentuated release of EDB-containing fibronectin by immune cells improved phagocytosis. In line with this, administration of EDB fibronectin enhanced in vitro phagocytosis to a larger extent than plasma fibronectin. This enhancement was mediated by αvβ3 integrin as shown using inhibitors or cells from β3 integrin knockout mice. Thus, we identified both a novel function for EDB fibronectin in augmenting phagocytosis over circulating plasma fibronectin, as well as the mediating receptor. Our data also establish for the first time, a direct role for β3 integrin in bacterial phagocytosis in mammals. Key messages • Fibronectin containing an extra domain called EDB is released in bacterial meningitis. • EDB-containing fibronectin enhances phagocytosis more than plasma fibronectin. • The enhancement is mediated by activation of αvβ3 integrin in the presence of EDB. Electronic supplementary material The online version of this article (doi:10.1007/s00109-015-1373-0) contains supplementary material, which is available to authorized users.

The actin cytoskeleton is a main component to preserve the cell shape. It represents a cellular machinery that enables morphological changes and orchestrates important dynamic cellular functions. Thereby, it supports T-cell migration, immune synapse formation, activation and execution of effector functions. The analysis of actin rearrangements in T-cells is therefore an important field of basic and clinical research. Actin reorganization is traditionally performed using flow cytometry or confocal microscopy. However, while flow cytometry lacks spatial and structural information, confocal microscopy is time consuming and not feasible for the characterization of rare events or of un-purified primary cell populations. Here we describe a methodology to analyze actin rearrangements using InFlow microscopy, which is a hybrid technique consisting of flow cytometric and microscopic features. We show that InFlow microscopy is a valuable tool for quantification of the amount and distribution of F-actin in human T-cells after stimulation with chemokines or antigen-presenting cells.

Innate immune cells can sense hepatitis C virus (HCV)-infected cells and respond with anti-viral actions including secretion of interferons (IFNs). In previous studies, the response of individual innate immune cells against HCV was analyzed in detail. We hypothesized that interaction of multiple innate immune cells increases the magnitude of the immune response and eventually leads to clearance of HCV-infected cells. To investigate this, we co-cultured Huh-7 HCV subgenomic replicon (SGR) cells with peripheral blood mononuclear cells (PBMCs). We confirm secretion of IFNα by plasmacytoid dendritic cells (pDCs) and IFNγ by natural killer (NK) cells in the co-culture setup. Moreover, we observed that also monocytes contribute to the anti-viral response. Flow cytometry and ImageStream analysis demonstrated that monocytes take up material from HCV SGR cells in co-culture with PBMCs. Preceding the uptake, PBMCs caused apoptosis of HCV SGR cells by tumor necrosis factor-related apoptosis inducing ligand (TRAIL) expression on NK cells. We observed that only the interplay of monocytes, pDCs, and NK cells resulted in efficient clearance of HCV SGR cells, while these cell populations alone did not kill HCV SGR cells. Despite similar TRAIL receptor expression on Huh-7 control cells and HCV SGR cells, HCV activated PBMCs specifically killed HCV SGR cells and did not target Huh-7 control cells. Finally, we showed that HCV replicating cells per se are sensitive toward TRAIL-induced apoptosis. Our results highlight the importance of the interplay of different innate immune cells to initiate an efficient, rapid, and specific response against HCV-infected cells.

Interaction of short-wavelength free-electron laser (FEL) beams with matter is undoubtedly a subject to extensive investigation in last decade. During the interaction various exotic states of matter, such as warm dense matter, may exist for a split second. Prior to irreversible damage or ablative removal of the target material, complicated electronic processes at the atomic level occur. As energetic photons impact the target, electrons from inner atomic shells are almost instantly photo-ionized, which may, in some special cases, cause bond weakening, even breaking of the covalent bonds, subsequently result to so-called non-thermal melting. The subject of our research is ablative damage to lead tungstate (PbWO4) induced by focused short-wavelength FEL pulses at different photon energies. Post-mortem analysis of complex damage patterns using the Raman spectroscopy, atomic-force (AFM) and Nomarski (DIC) microscopy confirms an existence of non-thermal melting induced by high-energy photons in the ionic monocrystalline target. Results obtained at Linac Coherent Light Source (LCLS), Free-electron in Hamburg (FLASH), and SPring-8 Compact SASE Source (SCSS) are presented in this Paper.

The clearance of tumors or virus infected cells is a crucial task of the immune system. Cytotoxic T-cells (CTLs) are able to detect and to kill such altered host cells. Given the recent success of checkpoint inhibitors for tumor therapy, it becomes more and more important to understand the biology of T-cell mediated target cell killing. Tests that allow analyzing the biology of CTLs are either based on flow cytometry or fluorescence microscopy. Thus, they either lack image-based information or have a poor statistical robustness. Therefore, we describe an approach to quantify CTL-mediated cytotoxicity using imaging flow cytometry. Using activated primary human cytotoxic T-cells as CTLs and P815 as target cells, we show that both the evaluation of target cell death and the biology of CTLs can be evaluated in parallel. This enables to gain information about CTL-mediated cytotoxicity in samples from patients important for translational medicine. J. Cell. Biochem. 118: 2528-2533, 2017. © 2017 Wiley Periodicals, Inc.

Silicon crystalline samples were exposed to intense single pulses of XUV radiation ( λ =13.5 nm) what lead to melting and ablation of the surface material. The deformation field around craters along the whole thickness of silicon wafers was observed by means of the synchrotron transmission section topography using the beam perpendicular to the surface of the sample. The geometrical shape and depth extension around craters was evaluated based on numerous, dense series of section topographs spaced by 10 µm. In the topographs we observed the direct image connected with the boundary of the crater associated with some deformation of the Kato fringes. The evaluated depth extension, different for individual craters, was in the range of 30–100 µm. The depth values were confirmed also by evaluations based on the Bragg case section topographs. It was possible to reproduce the contrast of the craters in transmission section topographs by numerical simulation based on integration of the Takagi–Taupin equations. The damage of the crystal defects connected with craters was approximated as droplet-like inclusions.

Cofilin is an actin-binding protein that depolymerizes and/or severs actin filaments. This dual function of cofilin makes it one of the major regulators of actin dynamics important for T-cell activation and migration. The activity of cofilin is spatio-temporally regulated. Its main control mechanisms comprise a molecular toolbox of phospho-, phospholipid, and redox regulation. Phosphorylated cofilin is inactive and represents the dominant cofilin fraction in the cytoplasm of resting human T cells. A fraction of dephosphorylated cofilin is kept inactive at the plasma membrane by binding to phosphatidylinositol 4,5-bisphosphate. Costimulation via the T-cell receptor/CD3 complex (signal 1) together with accessory receptors (signal 2) or triggering through the chemokine SDF1α (stromal cell-derived factor 1α) induce Ras-dependent dephosphorylation of cofilin, which is important for immune synapse formation, T-cell activation, and T-cell migration. Recently, it became evident that cofilin is also highly sensitive for microenvironmental changes, particularly for alterations in the redox milieu. Cofilin is inactivated by oxidation, provoking T-cell hyporesponsiveness or necrotic-like programmed cell death. In contrast, in a reducing environment, even phosphatidylinositol 4,5-bisphosphate -bound cofilin becomes active, leading to actin dynamics in the vicinity of the plasma membrane. In addition to the well-established three signals for T-cell activation, this microenvironmental control of cofilin delivers a modulating signal for T-cell-dependent immune reactions. This fourth modulating signal highly impacts both initial T-cell activation and the effector phase of T-cell-mediated immune responses.

Immune cells need to communicate with each other via direct cell contact formation. The contact zone has similar functions as a neuronal synapse and is therefore named immune synapse. Supramolecular activation clusters consisting of a variety of surface receptors and cytoplasmic proteins are formed within the immune synapse, which are pivotal for T-cell activation. Thus, a malfunction of immune synapse formation has detrimental effects on the healthiness of the individual.Classical confocal microscopy to analyze the supramolecular cluster formation and maturation of the immune synapse between primary human T-cells and antigen-presenting cells is time consuming and the number of cells that can be analyzed is limited. Therefore, we have established an InFlow microscopy approach for the analysis of immune synapses. InFlow microscopy is a hybrid method combining fluorescence microscopy and flow cytometry. Our InFlow microscopy method allows quantifying protein distribution in immune synapses of several hundred or even thousand cell couples in one sample. Importantly, comparisons of different samples with a strong statistical power are possible with InFlow microcopy.

Cytotoxic T-cells (CTLs) play an important role in many immune-mediated inflammatory diseases. Targeting cytotoxicity of CTLs would allow to interfere with immune-mediated tissue destruction. Here we demonstrate that WF-10, a pro-oxidative compound, inhibits CTL-mediated cytotoxicity. WF-10 did not influence early steps of target-cell killing, but impaired the ability of CTLs to detach from the initial target cell and to move to a second target cell. This reduced serial killing was accompanied by stronger enrichment of the adhesion molecule LFA-1 in the cytolytic immune synapse. LFA-1 clustering requires activation of the actin-bundling protein L-plastin and was accordingly diminished in L-plastin knockdown cells. Interestingly, WF-10 likely acts through regulating L-plastin: (I) It induced L-plastin activation through phosphorylation leading to enhanced LFA-1-mediated cell adhesion, and, importantly, (II) WF-10 lost its influence on target-cell killing in L-plastin knockdown cells. Finally, we demonstrate that WF-10 can improve immunosuppression by conventional drugs. Thus, while cyclosporine A alone had no significant effect on cytotoxicity of CTLs, a combination of cyclosporine A and WF-10 blocked target-cell killing synergistically. Together, our findings suggest that WF-10 – either alone or in combination with conventional immunosuppressive drugs – may be efficient to control progression of diseases, in which CTLs are crucially involved.

Fibronectin is a multidomain protein secreted by various cell types. It forms a network of fibers within the extracellular matrix and impacts intracellular processes by binding to various molecules, primarily integrin receptors on the cells. Both the presence of several isoforms and the ability of the various domains and isoforms to bind to a variety of integrins result in a wide range of effects. In vivo findings suggest that fibronectin isoforms produced by the osteoblasts enhance their differentiation. Here we report that the isoform characterized by the presence of extradomain A activates α4β1 integrin and augments osteoblast differentiation. In addition, the isoform containing extradomain B enhances the binding of fibronectin through the RGD sequence to β3-containing integrin, resulting in increased mineralization by and differentiation of osteoblasts. Our study thus reveals novel functions for two fibronectin isoforms and the mediating receptors in osteoblast differentiation.

Unlike activated CD4(+) T cells, resting CD4(+) T cells are highly resistant to productive HIV-1 infection. Early after HIV-1 entry, a major block limits reverse transcription of incoming viral genomes. Here we show that the deoxynucleoside triphosphate triphosphohydrolase SAMHD1 prevents reverse transcription of HIV-1 RNA in resting CD4(+) T cells. SAMHD1 is abundantly expressed in resting CD4(+) T cells circulating in peripheral blood and residing in lymphoid organs. The early restriction to infection in unstimulated CD4(+) T cells is overcome by HIV-1 or HIV-2 virions into which viral Vpx is artificially or naturally packaged, respectively, or by addition of exogenous deoxynucleosides. Vpx-mediated proteasomal degradation of SAMHD1 and elevation of intracellular deoxynucleotide pools precede successful infection by Vpx-carrying HIV. Resting CD4(+) T cells from healthy donors following SAMHD1 silencing or from a patient with Aicardi-Goutières syndrome homozygous for a nonsense mutation in SAMHD1 were permissive for HIV-1 infection. Thus, SAMHD1 imposes an effective restriction to HIV-1 infection in the large pool of noncycling CD4(+) T cells in vivo. Bypassing SAMHD1 was insufficient for the release of viral progeny, implicating other barriers at later stages of HIV replication. Together, these findings may unveil new ways to interfere with the immune evasion and T cell immunopathology of pandemic HIV-1.

SummarySignal transduction to nuclear factor-kappa B (NF-κB) involves multiple kinases and phosphorylated target proteins, but little is known about signal termination by dephosphorylation. By RNAi screening, we have identified protein phosphatase 4 regulatory subunit 1 (PP4R1) as a negative regulator of NF-κB activity in T lymphocytes. PP4R1 formed part of a distinct PP4 holoenzyme and bridged the inhibitor of NF-κB kinase (IKK) complex and the phosphatase PP4c, thereby directing PP4c activity to dephosphorylate and inactivate the IKK complex. PP4R1 expression was triggered upon activation and proliferation of primary human T lymphocytes and deficiency for PP4R1 caused sustained and increased IKK activity, T cell hyperactivation, and aberrant NF-κB signaling in NF-κB-addicted T cell lymphomas. Collectively, our results unravel PP4R1 as a previously unknown activation-associated negative regulator of IKK activity in lymphocytes whose downregulation promotes oncogenic NF-κB signaling in a subgroup of T cell lymphomas.

The amino acid arginine is fundamentally involved in the regulation of the immune response during infection, inflammatory diseases and tumor growth. Arginine deficiency (e.g. due to the myeloid cell enzyme arginase) inhibits proliferation and effector functions of activated T lymphocytes. Here, we studied intracellular mechanisms mediating this suppression of human T lymphocytes. Our proteomic analysis revealed an impaired dephosphorylation of the actin-binding protein cofilin upon T-cell activation in the absence of arginine. We show that this correlates with alteration of actin polymerization and impaired accumulation of CD2 and CD3 in the evolving immunological synapse in T cell-antigen presenting cells conjugates. In contrast, T-cell cytokine synthesis is differentially regulated in human T lymphocytes in the absence of arginine. While the production of certain cytokines (e.g. IFN-γ) is severely reduced, T lymphocytes produce other cytokines (e.g. IL-2) independent of extracellular arginine. MEK and PI3K activity are reciprocally regulated in association with impaired cofilin dephosphorylation. Finally, we show that impaired cofilin dephosphorylation is also detectable in human T cells activated in a granulocyte-dominated purulent micromilieu due to arginase-mediated arginine depletion. Our novel results identify cofilin as a potential regulator of human T-cell activation under conditions of inflammatory arginine deficiency.

An important problem in the experiments performed with the intense fourth generation X-ray sources is the damages of the examined samples caused by the high energy impact. The effect introduced by the beam from the FLASH source in crystalline silicon samples was studied through synchrotron white beam projection and section topography, enabling the evaluation of the strain field associated with the damages. The topographs indicated the existence of deformed field of cylindrical symmetry providing the dark contrast. It was also shown that some of the Bragg-case section images of spots in silicon correspond well to the simulated images of rod-like inclusions.

Activation of naïve T cells requires costimulation via TCR/CD3 plus accessory receptors, which enables the dynamic rearrangement of the actin cytoskeleton and immune synapse maturation. Signaling events induced following costimulation may thus be valuable targets for therapeutic immunosuppression. Phosphorylation of the actin-bundling protein L-plastin represents such a costimulatory signal in primary human T cells. Phosphorylated L-plastin has a higher affinity toward F-actin. However, the importance of the L-plastin phosphorylation for actin cytoskeleton regulation upon antigen recognition remained unclear. Here, we demonstrate that phosphorylation of L-plastin is important for immune synapse maturation. Thus, expression of nonphosphorylatable L-plastin in untransformed human peripheral blood T cells leads to reduced accumulation of LFA-1 in the immune synapse and to a diminished F-actin increase upon T-cell activation. Interestingly, L-plastin phosphorylation is inhibited by the glucocorticoid dexamethasone. In line with this finding, dexamethasone treatment leads to a reduced F-actin content in stimulated T cells and prevents maturation of the immune synapse. This inhibitory effect of dexamethasone could be reverted by expression of a phospho-mimicking L-plastin mutant. In conclusion, our data introduce costimulation-induced L-plastin phosphorylation as an important event for immune synapse formation and its inhibition by dexamethasone as a novel mode of function of this immunosuppressive glucocorticoid.

We report a comprehensive investigation of the electronically excited states of helium clusters and droplets of sizes ranging from a few to several 10(7) atoms using time-resolved fluorescence excitation spectroscopy and quantum chemical ab initio calculations. We employ various approaches for our analysis considering the lifetime-dependence of the fluorescence intensity, spectral shifts, intensity scaling with cluster size, isotopic dependence, and density-dependence of the calculated electron wave function radii. A unique feature of helium clusters and droplets is their radially varying particle density. Our results show that short-lived fluorescence is sensitive to regions of increased density and probes excitations located in the bulk volume, whereas long-lived fluorescence is sensitive to regions of reduced density such as for small clusters or for the surface of large droplets. Spectra of (3)He droplets serve as a reference for low density, but are free from contributions of small clusters. This allows us to distinguish regions of reduced density as these can be due to both surface states or small clusters. Our analysis reveals a picture where spectral features are related to regions of different density due to isotopic composition, cluster size, and surface or bulk volume location of the excitations. The 2s and 2p related excitations appear as blue-shifted wings for small clusters or for excited atoms within the surface layer, whereas in the bulk-volume of large droplets, they appear as distinct bands with large intensities, dominating the entire spectrum. Excitations at energies higher than 23 eV are unambiguously assigned to regions of low and medium density location within the deeper parts of the surface layer but show no relation to the bulk volume. Our findings support the idea that in liquid helium high-lying states and, in particular, Rydberg states are quenched in favor of the 2s and 2p excitations.

The atomic force microscopy (AFM) is a powerful tool to analyze forces generated on cellular interactions on the single-cell level. This highly sensitive device can record changes in force in the pico-Newton range, which equals single molecule bonds. Here, we have used single-cell force spectroscopy by AFM to investigate the interaction between T cells and tumor cells that is induced by the bispecific antibody HEA125xOKT3 (specificity anti-EpCAMxCD3). We show that HEA125xOKT3 induces a specific increase in adhesion force between T cells and cancer cells. The adhesive force that is generated on cell-cell contact is dependent on the applied force on initial contact and the duration of this initial contact. In summary, HEA125xOKT3 has been found to mediate contact formation by distinct processes. It induces direct cell-cell interaction, which results in the activation of T-cell signaling, facilitates the formation of supramolecular activation clusters and ultimately of an immune synapse.

Dendritic cells (DCs) are key components of the adaptive immune system contributing to initiation and regulation of T cell responses. T cells continuously scan DCs in lymphoid organs for the presence of foreign antigen. However, little is known about the functional consequences of these frequent T cell–DC interactions without cognate antigen. Here we demonstrate that these contacts in the absence of foreign antigen serve an important function, namely, induction of a basal activation level in T cells required for responsiveness to subsequent encounters with foreign antigens. This basal activation is provided by self-recognition of MHC molecules on DCs. Following DC depletion in mice, T cells became impaired in TCR signaling and immune synapse formation, and consequently were hyporesponsive to antigen. This process was reversible, as T cells quickly recovered when the number of DCs returned to a normal level. The extent of T cell reactivity correlated with the degree of DC depletion in lymphoid organs, suggesting that a full DC compartment guarantees optimal T cell responsiveness. These findings indicate that DCs are specialized cells that not only present foreign antigen, but also promote a “tonic” state in T cells for antigen responsiveness.

Bacteria organised in biofilms are a common cause of relapsing or persistent infections, particularly in patients receiving medical implants such as ventilation tubes, indwelling catheters, artificial heart valves, endoprostheses, or osteosynthesis materials. Bacteria in biofilms are relatively resistant towards antibiotics and biocides, and--according to the current dogma--towards the host defence mechanisms as well. In that context, we addressed the question, how polymorphonuclear neutrophils (PMN), the "first line defence" against bacterial infection, would interact with Staphylococcus aureus biofilms generated in vitro. By time-lapse video microscopy and confocal laser scan microscopy we observed a migration of PMN towards and into the biofilms, as well as clearance of biofilms by phagocytosis. By labelling the bacteria within the biofilm with (3)H thymidine, and by cytofluorometry we could confirm and quantify clearance and phagocytosis of biofilm as well. Of note, the extent of biofilm clearance depended on its maturation state: developing "young" biofilms were more sensitive towards the attack by PMN compared to mature biofilms. In conclusion, contrary to the current dogma, S. aureus biofilms are not inherently protected against the host defence.

SummaryOxidative stress leads to impaired T cell activation. A central integrator of T cell activation is the actin-remodelling protein cofilin. Cofilin is activated through dephosphorylation at Ser3. Activated cofilin enables actin dynamics through severing and depolymerization of F-actin. Binding of cofilin to actin is required for formation of the immune synapse and T cell activation. Here, we showed that oxidatively stressed human T cells were impaired in chemotaxis- and costimulation-induced F-actin modulation. Although cofilin was dephosphorylated, steady-state F-actin levels increased under oxidative stress conditions. Mass spectrometry revealed that cofilin itself was a target for oxidation. Cofilin oxidation induced formation of an intramolecular disulfide bridge and loss of its Ser3 phosphorylation. Importantly, dephosphorylated oxidized cofilin, although still able to bind to F-actin, did not mediate F-actin depolymerization. Impairing actin dynamics through oxidation of cofilin provides a molecular explanation for the T cell hyporesponsiveness caused by oxidative stress.

We investigated tolerability and efficacy of ezetimibe treatment (10 mg/d) in 25 heart allograft recipients already on stable statin therapy. Total cholesterol (TC), low-density cholesterol (LDL-C), high-density cholesterol (HDL-C), triglycerides (TG), immunosuppressant drug levels, laboratory and clinical parameters were assessed before, four months and one yr after initiation of ezetimibe treatment. Mean equivalent statin dose was 53.5 +/- 12.3 mg of pravastatin, remaining unchanged throughout the study period. Ezetimibe was generally well tolerated, only two patients (8%) discontinued ezetimibe due to stomach pain or headache. Mean TC decreased from 231.8 +/- 6.4 mg/dL before therapy to 202.2 +/- 8.8 mg/dL after four months and 192.9 +/- 7.0 mg/dL after one yr (p < 0.001). Mean LDL-C decreased from 143.1 +/- 5.4 mg/dL to 121.4 +/- 7.9 mg/dL (month 4; p < 0.05) and 107.1 +/- 5.6 mg/dL (one yr; p < 0.001). TG decreased from 182 +/- 14.3 mg/dL to 173.3 +/- 17.5 mg/dL after one yr (p < 0.05), whereas HDL-C was unchanged. Initial LDL-C and cardiac diagnosis before transplantation were identified as predictors of absolute LDL-C reduction. Immunosuppressant drug doses and blood concentrations were unchanged as well as other laboratory and clinical parameters. Ezetimibe appears safe and effective for further reduction of TC and LDL-C in heart allograft recipients already on stable statin therapy. Extent of pre-treatment LDL-C and cardiac disorder prior to transplantation appear to correlate with the efficacy of ezetimibe therapy.

Dynamic analysis of redox-based processes in living cells is now restricted by the lack of appropriate redox biosensors. Conventional redox-sensitive GFPs (roGFPs) are limited by undefined specificity and slow response to changes in redox potential. In this study we demonstrate that the fusion of human glutaredoxin-1 (Grx1) to roGFP2 facilitates specific real-time equilibration between the sensor protein and the glutathione redox couple. The Grx1-roGFP2 fusion protein allowed dynamic live imaging of the glutathione redox potential (E(GSH)) in different cellular compartments with high sensitivity and temporal resolution. The biosensor detected nanomolar changes in oxidized glutathione (GSSG) against a backdrop of millimolar reduced glutathione (GSH) on a scale of seconds to minutes. It facilitated the observation of redox changes associated with growth factor availability, cell density, mitochondrial depolarization, respiratory burst activity and immune receptor stimulation.

Fluorescence molecular brain imaging is a new modality allowing the detection of specific contrast agents down to very low concentration ranges (picomolar) in disease models. Here we demonstrate a first noninvasive application of fluorescence imaging in the human brain, where concentrations down to about 100 nM of a nonspecific dye were detected. We argue that due to its high sensitivity, optical molecular imaging of the brain is feasible, which – together with its bedside applicability – makes it a promising technique for use in patients.

We review development of multimillijoule X-ray lasers and of applications of these new laboratory sources carried out recently at the PALS facility. A backbone of this development is the neon-like zinc laser providing saturated output at 21.2 nm, with up to 10 mJ of energy per pulse. This represents currently the most energetic soft X-ray laboratory source. Recent improvements in its operation include better control of the beam shape, and more complete understanding of the prepulse pumping. The laser at 21.2 nm has been employed for a number of application experiments reviewed in this paper. They include transmission measurements of intense soft X-ray radiation, studies of fundamental processes of soft X-ray ablation, ablation micropatterning, feasibility study of soft X-ray Thomson scattering from dense plasmas, visualization of nanometric transient perturbation of optical surfaces, measurements of ablation rates of foils heated by IR pulses, and studies of 2D plasma hydrodynamics in the regime of sequen...

Rearrangements in the actin cytoskeleton play a pivotal role for costimulation-induced formation of the immunological synapse and T cell activation. Yet, little is known about the actin-binding proteins that link costimulation to rearrangements in the actin cytoskeleton. Here we demonstrate that phosphorylation of the actin bundling protein L-plastin in response to costimulation through TCR/CD3 plus CD2 or CD28, respectively, is important for the activation of human peripheral blood T lymphocytes (PBT). Mass spectrometry and site-directed mutagenesis revealed that Ser5 represents the only phospho-acceptor site of L-plastin in PBT. Wild-type L-plastin (wt-LPL) and a non-phosphorylatable 5A-L-plastin (5A-LPL) equally relocalized to the immunological synapse between PBT and APC. Yet importantly, cells expressing 5A-LPL showed a significantly lower expression of the T cell activation molecules CD25 and CD69 on the cell surface than cells expressing wt-LPL. This effect is due to a failure in the transport of CD25 and CD69 to the cell surface since the total amount of these proteins within the cells remained unchanged. In conclusion, phosphorylation of the actin bundling protein L-plastin represents a so-far-unknown mechanism by which costimulation controls the transport of activation receptors to the T cell surface.

Summary Objectives : The study of neurovascular coupling greatly benefits from combined measurements of neuronal and vascular signals. Two-step signal processing is developed to extract parameters describing the coupling. Methods : Using a magnetometer in an extremely well shielded room a broadband magnetoencephalogram was simultaneously measured with time-resolved nearinfrared spectroscopy during a motor activity paradigm. The raw MEG and NIRS data were denoised separately using independent component analysis. Results : After averaging the resulting signals showed motor activity-related changes. The temporal correspondence between MEG and NIRS was assessed plotting a combined trajectory and calculating a crosscorrelation. Compared to the MEG signal, at movement onset the NIRS signal showed an onsetdelay in the range of seconds. Conclusions : Multi-variate signal pre-processing followed by temporal delay estimates demonstrated the extraction of neurovascular coupling parameters.

The leukocyte specific actin-binding protein L-plastin is aberrantly expressed in several nonhematopoetic malignant tumors. However, little is known about the functional consequences of L-plastin expression. Here, we investigated the function of L-plastin in human malignant melanoma cells. Knock-down of endogenous L-plastin by siRNA treatment reduced migration of the melanoma cell line IF6. However, in melanoma patients, no correlation existed between L-plastin expression and tumor stages. This implied that additional factors such as phosphorylation of L-plastin may influence its function in tumor cells. To investigate this further, EGFP-tagged wild-type L-plastin (wt-LPL-EGFP) and a mutated, nonphosphorylatable L-plastin protein (5A7A-LPL-EGFP), were expressed in the L-plastin negative melanoma cell line MV3. Biochemical analysis revealed that wt-LPL-EGFP is phosphorylated in MV3 cells while 5A7A-LPL-EGFP is not. Although both wt-LPL-EGFP and 5A7A-LPL-EGFP were targeted to, and promote the formation of, vinculin-containing adhesion sites, static adhesion to either Matrigel or isolated extracellular matrix molecules was neither influenced by expression of wt-LPL-EGFP nor by expression of 5A7A-LPL-EGFP when compared with EGFP expressing control cells. In contrast, haptotactic, but not chemotactic, migration of melanoma cells towards either Matrigel or isolated extracellular matrix molecules was similarly enhanced, if either 5A7A-LPL-EGFP or wt-LPL-EGFP were expressed in MV3 cells. Interestingly, only cells expressing the phosphorylatable wt-LPL-EGFP protein showed enhanced invasion into Matrigel. In line with these findings the in vivo metastatic capacity of mouse B16 melanoma cells correlates with expression and phosphorylation of L-plastin. These data show that an increase in melanoma cell invasiveness requires not only expression but also phosphorylation of L-plastin.

Immune cells need to communicate with each other via direct cell contact formation. The contact zone has similar functions as a neuronal synapse and is therefore named immune synapse. Supramolecular activation clusters consisting of a variety of surface receptors and cytoplasmic proteins are formed within the immune synapse, which are pivotal for T-cell activation. Thus, a malfunction of immune synapse formation has detrimental effects on the healthiness of the individual.Classical confocal microscopy to analyze the supramolecular cluster formation and maturation of the immune synapse between primary human T-cells and antigen-presenting cells is time consuming and the number of cells that can be analyzed is limited. Therefore, we have established an InFlow microscopy approach for the analysis of immune synapses. InFlow microscopy is a hybrid method combining fluorescence microscopy and flow cytometry. Our InFlow microscopy method allows quantifying protein distribution in immune synapses of several hundred or even thousand cell couples in one sample. Importantly, comparisons of different samples with a strong statistical power are possible with InFlow microcopy.