Negative Costimulation Research Articles

ВЛИЯНИЕ ДЛИТЕЛЬНОГО КОСМИЧЕСКОГО ПОЛЕТА НА СТАНОВЛЕНИЕ И РАЗВИТИЕ Т-КЛЕТОЧНОГО ИММУНИТЕТА ЧЕЛОВЕКА

The authors present the results of studying the processes involved in maturation of dendritic cells (DCs) derived from CD14+-monocytes and TCR-activation of peripheral blood lymphocytes from 9 ISS Russian crew members. It was demonstrated that long-term habitation on low Earth's orbits brings about disorders both in DCs and Т-lymphocytes evidenced by reductions in mature DCs expressing the В7 family of co-stimulating molecules and also Т-lymphocytes expressing the molecules of positive CD28 co-stimulation. The investigation found an increased number of tolerogenic DCs with the CD80+CD86- immunophenotype and T-cells expressing the negative co-stimulation molecules CD152. TCR-stimulation of lymphocytes in vitro enabled detection of changes in the processes of associated with T-lymphocyte differentiation and synthesis of cytokines. The immune system reaction to prolonged exposure to the aggregate of spaceflight factors was distinctively individual.

Small Gene Networks Delineate Immune Cell States and Characterize Immunotherapy Response in Melanoma.

Single-cell technologies have elucidated mechanisms responsible for immune checkpoint inhibitor (ICI) response, but are not amenable to a clinical diagnostic setting. In contrast, bulk RNA sequencing (RNA-seq) is now routine for research and clinical applications. Our workflow uses transcription factor (TF)-directed coexpression networks (regulons) inferred from single-cell RNA-seq data to deconvolute immune functional states from bulk RNA-seq data. Regulons preserve the phenotypic variation in CD45+ immune cells from metastatic melanoma samples (n = 19, discovery dataset) treated with ICIs, despite reducing dimensionality by >100-fold. Four cell states, termed exhausted T cells, monocyte lineage cells, memory T cells, and B cells were associated with therapy response, and were characterized by differentially active and cell state-specific regulons. Clustering of bulk RNA-seq melanoma samples from four independent studies (n = 209, validation dataset) according to regulon-inferred scores identified four groups with significantly different response outcomes (P < 0.001). An intercellular link was established between exhausted T cells and monocyte lineage cells, whereby their cell numbers were correlated, and exhausted T cells predicted prognosis as a function of monocyte lineage cell number. The ligand-receptor expression analysis suggested that monocyte lineage cells drive exhausted T cells into terminal exhaustion through programs that regulate antigen presentation, chronic inflammation, and negative costimulation. Together, our results demonstrate how regulon-based characterization of cell states provide robust and functionally informative markers that can deconvolve bulk RNA-seq data to identify ICI responders.

Costimulators expressed on human endothelial cells modulate antigen-dependent recruitment of circulating T lymphocytes.

Endothelial cells (ECs) can present antigens to circulating effector memory T cells (TEM) and to regulatory T cells (T regs), triggering antigen-specific extravasation at specific sites where foreign antigens are introduced, e.g. by infection or transplantation. We model human antigen-induced transendothelial migration (TEM) using presentation of superantigen by cultured human dermal microvascular (HDM)ECs to isolated resting human peripheral blood T cell subpopulations or to T effector cells activated in vitro. T cell receptor (TCR)-mediated cytokine synthesis, a common assay of T cell activation by antigen, is modulated by antigen-independent signals provided by various positive or negative costimulator proteins (the latter known as checkpoint inhibitors) expressed by antigen presenting cells, including ECs. We report here that some EC-expressed costimulators also modulate TCR-TEM, but effects differ between TEM and cytokine production and among some T cell types. Blocking EC LFA-3 interactions with TEM CD2 boosts TEM but reduces cytokine production. Blocking EC ICOS-L interactions with TEM CD28 (but not ICOS) reduces both responses but these involve distinct CD28-induced signals. Activated CD4+ T effector cells no longer undergo TCR-TEM. Engagement of T cell CD28 by EC ICOS-L increases TCR-TEM by activated CD8 effectors while engagement of OX40 promotes TCR-TEM by activated CD4 T regs. B7-H3 mostly affects TEM of resting TEM and some checkpoint inhibitors affect cytokine synthesis or TEM depending upon subtype. Our data suggest that blockade or mimicry of costimulators/checkpoint inhibitors in vivo, clinically used to modulate immune responses, may act in part by modulating T cell homing.

IFNγ-Stimulated B Cells Inhibit T Follicular Helper Cells and Protect Against Atherosclerosis.

B and T cells are interconnected in the T follicular helper—germinal center B cell (TFH-GC B cell) axis, which is hyperactive during atherosclerosis development and loss of control along this axis results in exacerbated atherosclerosis. Inhibition of the TFH–GC B cell axis can be achieved by providing negative co-stimulation to TFH cells through the PD-1/PD-L1 pathway. Therefore, we investigated a novel therapeutic strategy using PD-L1-expressing B cells to inhibit atherosclerosis. We found that IFNγ-stimulated B cells significantly enhanced PD-L1 expression and limited TFH cell development. To determine whether IFNγ-B cells can reduce collar-induced atherosclerosis, apoE−/− mice fed a Western-type diet were treated with PBS, B cells or IFNγ-B cells for a total of 5 weeks following collar placement. IFNγ-B cells significantly increased PD-L1hi GC B cells and reduced plasmablasts. Interestingly, IFNγ-B cells–treated mice show increased atheroprotective Tregs and T cell-derived IL-10. In line with these findings, we observed a significant reduction in total lesion volume in carotid arteries of IFNγ-B cells-treated mice compared to PBS-treated mice and a similar trend was observed compared to B cell-treated mice. In conclusion, our data show that IFNγ-stimulated B cells strongly upregulate PD-L1, inhibit TFH cell responses and protect against atherosclerosis.

A CTLA-4 blocking strategy based on Nanobody in dendritic cell-stimulated cytokine-induced killer cells enhances their anti-tumor effects

BackgroundCytokine-induced killer cells induced with tumor antigen-pulsed dendritic cells (DC-CIK) immunotherapy is a promising strategy for the treatment of malignant tumors. However, it sefficacy is restricted by the immunosuppression, which is mediated by the cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) pathway. In order to overcome the negative co-stimulation from these T cells, we screened a nanobody targeted for CTLA-4 (Nb36) and blocked the CTLA-4 signaling with Nb36.MethodsPeripheral blood mononuclear cells (PBMCs) were collected from healthy donors to beused to induce CIK cells in vitro, after which they were co-cultured with DC cells that had received tumor antigens. In addition, we tested whether blocking CTLA-4 signaling with Nb36 could promote in vitro DC-CIK cells proliferation, pro-inflammatory cytokine production and cytotoxicity, or not. For the in vivo experiments, we constructed a subcutaneously transplanted tumor model and placed it in NOD/SCID mice to verify the anti-tumor effect of this therapy.ResultsAfter stimulation with Nb36, the DC-CIK cells presented enhanced proliferation and production of IFN-γ in vitro, which strengthened the killing effect on the tumor cells. For the in vivo experiments, it was found that Nb36-treated DC-CIK cells significantly inhibited the growth of subcutaneously transplanted livercancer tumors, as well as reduced the tumor weight and prolonged the survival of tumor-bearing NOD/SCID mice.ConclusionsOur findings demonstrated that in response to CTLA-4 specific nanobody stimulation, DC-CIK cells exhibited a better anti-tumor effect. In fact, this Nb-based CTLA-4 blocking strategy achieved an anti-tumor efficacy close to that of monoclonal antibodies. Our findings suggest that DC-CIK cells + Nb36 have the potential to treat malignant tumors through in vivo adoptive therapy.

Therapeutic dendritic cell cancer vaccines in hematologic malignancies

AbstractTumor cells present antigen in the context of negative costimulation and immunosuppressive factors, resulting in the inhibition of T cell activation and immune tolerance. Dendritic cells (DCs) are a complex network of antigen presenting cells that play a critical role in maintaining the equilibrium between immune activation directed against pathogens and tolerance necessary to prevent damage mediated by autoreactive T cell clones. DCs uniquely induce primary immune responses through the constitutive and enhanced expression of positive costimulatory molecules and inflammatory cytokines necessary for T cell activation. In this context, the design of a cancer vaccine is based on the effective presentation tumor associated antigens to evoke an antigen specific activated T cell response, and importantly, immune memory. As such, DCs have played a major role in the development of cancer vaccine therapy as critical mediators of antigen presentation reversing a major component of tumor mediated immune suppression. DC based vaccines have involved the loading of individual tumor associated antigens or the use of whole tumor cells and have demonstrated potent induction of tumor specific immunity. The correlation of immune response with clinical outcome and integration of DC vaccines with other immune based therapy is currently being explored.

High CD200 Expression on T CD4+ and T CD8+ Lymphocytes as a Non-Invasive Marker of Idiopathic Pulmonary Hypertension–Preliminary Study

Pulmonary arterial hypertension (PAH) can develop subsequently to disorganized endothelial cell proliferation within the pulmonary arteriolar layers that provide mechanical limits to the pulmonary vascular bed. Although the actual factor triggering vascular endothelial proliferation remains unknown to date, genetic susceptibility, hypoxia, inflammation, as well as response to drugs and toxins have been proposed as possible contributors. Since inflammation contributes to vascular remodeling, the changed immune response is increasingly considered a plausible cause of this cardiovascular disease. The interaction of a membrane glycoprotein cluster of differentiation 200 (CD200) and its structurally similar receptor (CD200R) plays a crucial role in the modulation of the inflammatory response. Our previous studies have shown that the overexpression of the other negative co-stimulatory molecule (programmed death cell-PD-1) and its ligand-1 (PD-L1) is closely related to iPAH and the presence of Epstein-Barr virus (EBV) reactivation markers. Therefore, we considered it necessary to analyze the different types of PAH in terms of CD200 and CD200R expression and to correlate CD200/CD200R pathway expression with important clinical and laboratory parameters. The CD200/C200R-signaling pathway has not been subject to much research. We included 70 treatment-naïve, newly diagnosed patients with PAH in our study. They were further divided into subsets according to the pulmonary hypertension classification: chronic thromboembolic pulmonary hypertension (CTEPH) subset, pulmonary arterial hypertension associated with congenital heart disease (CHD-PAH), pulmonary arterial hypertension associated with connective tissue disease (CTD-PAH), and idiopathic pulmonary arterial hypertension (iPAH). The control group consisted of 20 healthy volunteers matched for sex and age. The highest percentages of T CD200+CD4+ and T CD200+CD8+ lymphocytes were observed in the group of patients with iPAH and this finding was associated with the presence of EBV DNA in the peripheral blood. Our assessment of the peripheral blood lymphocytes expression of CD200 and CD200R indicates that these molecules act as negative co-stimulators in the induction and persistence of PAH-associated inflammation, especially that of iPAH. Similar results imply that the dysregulation of the CD200/CD200R axis may be involved in the pathogenesis of several immune diseases. Our work suggests that CD200 and CD200R expression may serve to distinguish between PAH cases. Thus, CD200 and CD200R might be useful as markers in managing PAH and should be further investigated.

Role of PD-L1 in Gut Mucosa Tolerance and Chronic Inflammation.

The gastrointestinal (GI) mucosa is among the most complex systems in the body. It has a diverse commensal microbiome challenged continuously by food and microbial components while delivering essential nutrients and defending against pathogens. For these reasons, regulatory cells and receptors are likely to play a central role in maintaining the gut mucosal homeostasis. Recent lessons from cancer immunotherapy point out the critical role of the B7 negative co-stimulator PD-L1 in mucosal homeostasis. In this review, we summarize the current knowledge supporting the critical role of PD-L1 in gastrointestinal mucosal tolerance and how abnormalities in its expression and signaling contribute to gut inflammation and cancers. Abnormal expression of PD-L1 and/or the PD-1/PD-L1 signaling pathways have been observed in the pathology of the GI tract. We also discuss the current gap in our knowledge with regards to PD-L1 signaling in the GI tract under homeostasis and pathology. Finally, we summarize the current understanding of how this pathway is currently targeted to develop novel therapeutic approaches.

A Nanobody Against Cytotoxic T-Lymphocyte Associated Antigen-4 Increases the Anti-Tumor Effects of Specific CD8+ T Cells.

Adoptive cell-based immunotherapy typically utilizes cytotoxic T lymphocytes (CTLs), expanding these cells ex vivo. Such expansion is traditionally accomplished through the use of autologous APCs that are capable of interactions with T cells. However, incidental inhibitory program such as CTLA-4 pathway can impair T cell proliferation. We therefore designed a nanobody which is specific for CTLA-4 (CTLA-4 Nb 16), and we then used this molecule to assess its ability to disrupt CTLA-4 signaling and thereby overcome negative costimulation of T cells. With CTLA-4 Nb16 stimulation, dendritic cell/hepatocellular carcinoma fusion cells (DC/HepG2-FCs) enhanced autologous CD8+ T cell proliferation and production of IFN-γ in vitro, thereby leading to enhanced killing of tumor cells. Using this approach in the context of adoptive CD8+ immunotherapy led to a marked suppression of tumor growth in murine NOD/SCID hepatocarcinoma or breast cancer xenograft models. We also observed significantly increased tumor cell apoptosis, and corresponding increases in murine survival. These findings thus demonstrate that in response to nanobody stimulation, DC/tumor cells-FC-induced specific CTLs exhibit superior anti-tumor efficacy, making this a potentially valuable means of achieving better adoptive immunotherapy outcomes in cancer patients.

Lower T cell inhibitory receptor level in mononuclear cells from cord blood compared with peripheral blood.

T cell inhibitory receptors play important role in maintaining T cell homeostasis. The feature of such negative costimulator signal transduction pathway in cord blood (CB) T cells remains unclear. In this study, the expression levels of T cell inhibitory receptors including programmed death-1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), T cell immunoglobulin mucin-3 (Tim-3), lymphocyte activation gene-3 (LAG-3) and B and T lymphocyte attenuator (BTLA) were characterized in CB and compared with peripheral blood (PB). Significant lower expression of PD-1, CTLA-4, LAG-3 and BTLA was found in CB, while similar expression level of Tim-3 was showed between CB and PB. Together, different expression pattern of such T cell inhibitory receptor in CB is worthy to further discuss their role on immune response when CB is used in cord blood stem cell transplantation as well as allogeneic chimeric antigen receptor T-cell producing.

Pembrolizumab-Induced Seronegative Arthritis and Fasciitis in a Patient with Lung Adenocarcinoma

Background: Immune checkpoint inhibitors (CPIs) are new promising anti-cancer drugs that block negative costimulation of T-cells leading to an enhanced anti-tumor immune response. Pembrolizumab, an a monoclonal antibody, targeting the programmed cell death protein 1 (PD-1) pathway. CPIs have been associated with a number of immune-related adverse events (AEs), including musculoskeletal and rheumatic disease.Objective: To present a case with lung adenocarcinoma treated with pembrolizumab, which developed inflammatory arthritis and fasciitis.Case Report: A 73-year-old male patient was referred to the rheumatology outpatient clinic with complaints of pain in the pretibial area, pain and swelling in both ankles joints and the right fırst metacarpophalangeal (MCP) joint. Three months ago he had diagnosed with lung adenocarcinoma and pembrolizumab was started. Locomotor system complaints were started after receiving two infusions of pembrolizumab. Physical examination revealed both ankle arthritis, mild edema in the pretibial region, tenderness in the muscles and arthritis in the right fırst MCP joint. Laboratory examinations showed mild acute phase reactants elevation. Lower extremity MRI showed diffuse edema in both gastrocnemius muscle and fascia, compatible with fasciitis. Pembrolizumab-related fasciitis and seronegative arthritis were diagnosed. Low dose corticosteroid was started and a significant regression was observed in the patient's complaints.Conclusion: Inflammatory myositis with fasciitis and inflammatory arthritis in lower extremities appears to be a new adverse effect of pembrolizumab therapy.

Negative Co-stimulation Constrains T Cell Differentiation by Imposing Boundaries on Possible Cell States

Co-stimulation regulates Tcell activation, but it remains unclear whether co-stimulatory pathways also control Tcell differentiation. We used mass cytometry to profile Tcells generated in the genetic absence of the negative co-stimulatory molecules CTLA-4 and PD-1. Our data indicate that negative co-stimulation constrains the possible cell states that peripheral Tcells can acquire. CTLA-4 imposes major boundaries on CD4+ Tcell phenotypes, whereas PD-1 subtly limits CD8+ Tcell phenotypes. By computationally reconstructing Tcell differentiation paths, we identified protein expression changes that underlied the abnormal phenotypic expansion and pinpointed when lineage choice events occurred during differentiation. Similar alterations in Tcell phenotypes were observed after anti-CTLA-4 and anti-PD-1 antibody blockade. These findings implicate negative co-stimulation as a key regulator and determinant of Tcell differentiation and suggest that checkpoint blockade might work in part by altering the limits of Tcell phenotypes.

Genome-wide analysis identifies NR4A1 as a key mediator of T cell dysfunction.

T cells become dysfunctional when they encounter self antigens or are exposed to chronic infection or to the tumour microenvironment1. The function of T cells is tightly regulated by a combinational co-stimulatory signal, and dominance of negative co-stimulation results in T cell dysfunction2. However, the molecular mechanisms that underlie this dysfunction remain unclear. Here, using an in vitro T cell tolerance induction system in mice, we characterize genome-wide epigenetic and gene expression features in tolerant T cells, and show that they are distinct from effector and regulatory T cells. Notably, the transcription factor NR4A1 is stably expressed at high levels in tolerant T cells. Overexpression of NR4A1 inhibits effector T cell differentiation, whereas deletion of NR4A1 overcomes T cell tolerance and exaggerates effector function, as well as enhancing immunity against tumour and chronic virus. Mechanistically, NR4A1 is preferentially recruited to binding sites of the transcription factor AP-1, where it represses effector-gene expression by inhibiting AP-1 function. NR4A1 binding also promotes acetylation of histone 3 at lysine 27 (H3K27ac), leading to activation of tolerance-related genes. This study thus identifies NR4A1 as a key general regulator in the induction of T cell dysfunction, and a potential target for tumour immunotherapy.

Enhancement of Cytomegalovirus-Specific Cytokine Production after Modulation of the Costimulation in Kidney Transplant Patients.

Kidney transplantation is the therapy of choice for patients with end stage renal disease. Due to immunosuppressive treatment, patients are at risk for opportunistic infections. Cytomegalovirus (CMV) reactivation is highly relevant in kidney transplant recipients because it occurs—depending on the serological constellation of the donor and recipient—in more than half of the patients and influences patient outcome. Patients with CMV reactivation show decreased allograft and overall survival. Previous studies could demonstrate that transplant patients often show weak CMV-specific immunity. Besides immunosuppressive treatment, additional mechanisms may reduce CMV-specific immunocompetence such as enhanced negative costimulation. Hence, the aim of this study was to investigate if the function of CMV-specific cells of kidney transplant recipients could be restored by a modulation of costimulatory molecules. To address this question, lymphocytes of kidney transplant patients were stimulated with CMV-specific antigens and incubated with programmed death-ligand 1 (PD-L1), programmed cell death protein 1 (PD-1), or B- and T-lymphocyte attenuator (BTLA) antibodies. Afterwards, the IFN-γ, IL-21, and IL-17A production was measured by the ELISpot assay. It could be shown that a blockade of the ligand PD-L1 resulted in an increased CMV-specific IFN-γ, IL-21, and IL-17A secretion. The blockade of the receptor PD-1 distinctly enhanced the production of IL-21. BTLA antibodies, however, led only to a marginal increase of CMV-specific IFN-γ and of IL-21 production. Experiments in healthy controls could confirm the results of the kidney transplant recipients. Furthermore, they could demonstrate that treatment with the immunosuppressive drug tacrolimus resulted in decreased CMV-specific IFN-γ and of IL-21 production. Thus, our study could show for the first time that the blockade of the PD-L1/PD-1 pathway also modulates CMV-specific Th21 and Th17 cell function in kidney transplant recipients. Further studies are mandatory to clarify the role of Th21 and Th17 cells in CMV control of these patients.

CD56-negative NK cells with impaired effector function expand in CMV and EBV co-infected healthy donors with age.

Natural killer cells lacking expression of CD56 (CD56neg NK cells) have been described in chronic HIV and hepatitis C virus infection. Features and functions of CD56neg NK cells in the context of latent infection with CMV and / or EBV with age are not known. In a cohort of healthy donors >60 years of age, we found that co-infection with CMV and EBV drives expansion of CD56neg NK cells. Functionally, CD56neg NK cells displayed reduced cytotoxic capacity and IFN-γ production, a feature that was enhanced with CMV / EBV co-infection. Further, the frequency of CD56neg NK cells correlated with accumulation of end-stage-differentiated T cells and a reduced CD4 / CD8 T cell ratio, reflecting an immune risk profile. CD56neg NK cells had a mature phenotype characterized by low CD57 and KIR expression and lacked characteristics of cell senescence. No changes in their activating NK cell receptor expression, and no upregulation of the negative co-stimulation receptors PD-1 or TIM-3 were observed. In all, our data identify expansion of dysfunctional CD56neg NK cells in CMV+EBV+ elderly individuals suggesting that these cells may function as shape-shifters of cellular immunity and argue for a previously unrecognized role of EBV in mediating immune risk in the elderly.

Molecular Dynamics of Co-signal Molecules in T-Cell Activation.

T-cell activation is induced through the TCR microcluster (TCR-MC), which is generated by dynamically recruiting the TCR, kinases, and adaptors to trigger the full activation signal. Co-stimulation receptors also accumulate, mostly at the TCR-MC, and induce signals that positively and negatively modulate the direction and magnitude of T-cell activation. CD28 initially colocalizes with the TCR-MC but then migrates to a distinct region of the cSMAC called the signaling cSMAC, where it recruits and associates with PKCθ, CARMA1, and Rltpr to induce sustainedco-stimulation signals leading to NF-kB activation. Although CTLA-4 and PD-1 mediate inhibitory functions in T-cell activation, their molecular dynamics are quite different. Both are expressed only after activation, when they function as feedback inhibition of T-cell activation. Whereas PD-1 initially accumulates in the TCR-MC and then moves to the cSMAC, CTLA-4 directly accumulates at the cSMAC. PD-1 inhibits activation by inducing dephosphorylation of TCR-upstream signaling molecules by transiently recruiting SHP2, whereas CTLA-4 competes with CD28 for CD80/86binding within the signaling cSMAC. In general, for both positive and negative co-stimulation, these co-stimulation receptors are also clustered in a ligand-dependent fashion, and their colocalization with the TCR-MC is required to mediate co-stimulation signals.

PD-1 and PD-L1 regulate cellular immunity in canine visceral leishmaniasis.

PD-1 is a negative costimulator of chronic infectious diseases In this study, we investigated the expression of PD-1 and its ligands in the spleen of dogs with visceral leishmaniasis and lymphoproliferative response to soluble antigen, in lymph node cells in the presence or absence of antibodies blocking PD-1 and its ligands. Our results showed expression of PD-1 and its ligands is higher after L. infantum infection and in the spleen of infected dogs, PD-1 blockage was able to restore the antigen-dependent lymphoproliferative response and regulated production of the cytokines IL-4 and IL-10 and NO production. We concluded that L. infantum infection modulates PD-1 and its ligands expression in canine VL and that blockage of PD-1 restores the immune response. Thus, blockage of PD-1 is a target for therapeutic drug development.

Negative costimulation constrains T cell differentiation

Abstract T cell costimulation is a principal mechanism by which T cell activation is regulated, but it remains unclear whether costimulatory pathways also control T cell differentiation. This unresolved question is germane to our understanding of how T cell function is controlled and has therapeutic implications in the context of cancer immunotherapy. Using a mass cytometry based systems approach and murine models we investigated whether negative costimulation regulates T cell differentiation as well as activation. Unsupervised population identification reveals 30 T cell subsets in Ctla-4−/− and littermate control mice including 6 CD8, 3 Treg, 14 CD4 effector T cell populations. Expectedly, loss of CTLA-4 led to dramatic changes in the relative frequency of CD8 and CD4 T cell subsets. Strikingly, however, loss of CTLA-4 led to the generation of multiple non-canonical T cell populations outside of the normal boundaries of T cell phenotypes, which interestingly, were all in the CD4 T compartment. To determine if the role of negative costimulation in differentiation may be a generalizable phenomenon, we performed similar analyses of Pdcd-1−/− mice. This profiling revealed that loss of PD-1 leads to a subtle expansion of CD8 T cell phenotypes in addition to changes in the relative frequencies of CD4 and CD8 T cell populations. These observations indicate that CTLA-4 restricts CD4 T cell phenotypes while PD-1 restricts CD8 T cell phenotypes. Consistent with this model, loss of CTLA-4 differentially affects the expression of individual markers in CD4 and CD8 T cells. Together these findings indicate that in addition to attenuating T cell activation, negative costimulation acts to constrain T cell differentiation.

B7-H1 Expression Is Required for Human Endometrial Regenerative Cells in the Prevention of Transplant Vasculopathy in Mice.

Vasculopathy is one of the primary pathological changes in chronic rejection of vascularized allograft transplantation. Endometrial regenerative cells (ERCs) are mesenchymal-like stromal cells with immunosuppressive effect. B7-H1 is a negative costimulator that mediates active immune suppression. The aim of this study was to investigate the requirement of B7-H1 in the immunoregulation of ERCs in preventing transplant vasculopathy of aorta allografts. The results showed that B7-H1 expression on ERCs was upregulated by IFN-γ in a dose-dependent manner and it was required for ERCs to inhibit the proliferation of peripheral blood mononuclear cells (PBMCs) in vitro. ERCs could alleviate transplant vasculopathy, as the intimal growth of transplanted aorta was limited, and the preventive effects were correlated with an increase in the percentages of CD11c+MHC class IIlowCD86low dendritic cells, CD68+CD206+ macrophages, and CD4+CD25+Foxp3+ T cells, as well as a decrease in the percentages of CD68+ macrophages, CD3+CD4+ T cells, CD3+CD8+ T cells, and donor-reactive IgM and IgG antibodies. Moreover, overexpression of B7-H1 by IFN-γ can promote the immunosuppressive effect of ERCs. These results suggest that overexpression of B7-H1 stimulated by IFN-γ is required for ERCs to prevent the transplant vasculopathy, and this study provides a theoretical basis for the future clinical use of human ERCs.

Decreased blood CD4+PD-1+ and CD8+PD-1+ T cells in psoriatic patients with and without arthritis.

IntroductionPsoriasis with and without arthritis have common immunological mechanisms which among others involve the interactions between cytokines produced by T cells, including Th1, Th17 and Th22. Although quite a lot is known about psoriasis pathogenesis, the cause of chronic immune activation and response in the disease remains unclear. One of the negative regulators of the immune system is programmed death 1 (PD-1).AimTo assess the expression level of PD-1 in the peripheral T cells of psoriatic patients with and without arthritis.Material and methodsThe study included 23 psoriatic patients with arthritis, 52 psoriatic patients without arthritis and 52 healthy controls. The percentages of CD3+, CD4+, CD8+, CD4+PD-1+ and CD8+PD-1+ T cells were analyzed using flow cytometry.ResultsThe percentages of CD4+PD-1+ as well as CD8+PD-1+ T cells in the psoriatic patients both with and without arthritis were significantly lower than in the control group. The percentages of CD4+PD-1+ as well as CD8+PD-1+T cells were not significantly different between the psoriatic patients with and without arthritis. A significant positive correlation between PD-1 expression on the CD4+ and CD8+ T cells was found in the psoriatic patients without arthritis.ConclusionsImpairment of the negative co-stimulation from PD-1 may be another common characteristic of psoriasis both with and without arthritis.