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Flagellin is an immunodominant Ag in Crohn disease, with many patients showing anti-flagellin Abs. To study the clonality of flagellin-reactive CD4 cells in Crohn patients, we used a common CD154-based enrichment method following short-term Ag exposure to identify Ag-reactive CD4 cells. CD154 expression and cytokine production following Ag exposure compared with negative control responses (no Ag exposure) revealed that only a small fraction of CD154-enriched cells could be defined by Ag-reactive cytokine responses. This was especially true for low-frequency flagellin-reactive CD4 cells compared with polyclonal stimulation or Candida albicans Ag exposure. Moreover, we found that culture conditions used for the assay contributed to background CD40L (CD154) expression in the CD154-enriched CD4 cells. Using a cut-off rule based on flow cytometry results of the negative control CD154-enriched CD4 cells, we could reliably find the fraction of Ag-reactive cells in the CD154-enriched population. Ag-reactive CD4 cytokine production was restricted to CD4 cells with an effector memory phenotype and the highest levels of induced CD154 expression. This has important implications for identifying Ag-specific T cells of interest for single cell cloning, phenotyping, and transcriptomics.

Background: We studied the expression of important costimulatory molecules of lymphocyte activation and the presence of CD16+ cells on aspiration biopsies of kidney transplants, measured three soluble factors and when indicated tested their robustness in diagnosing acute rejection. Methods: Fine-needle aspiration biopsies were performed either on days seven or 14 - 30 post-transplantation among stable kidney transplants and on the day of acute rejection diagnosis, while a sample of peripheral blood was collected simultaneously. The cyto preparations were studied by the enzymatic avidin biotin complex staining. The immunocytochemistry was directed to CD16, CD28, CD152, ICOS, CD40, CD154, CD26 and CD27. We performed the analysis in the peripheral blood by ELISA for soluble(s) CD16, CD26, and CD154. Results: The group of acute rejection cases showed a significant up-regulated expression of CD16, CD26, ICOS and CD40 as compared to the group of stable cases. Both sCD16 and sCD154 were significantly higher in the blood samples of the group with acute rejection. Thymoglobulin down-regulated CD154 and sCD16. CD16, CD26 and ICOS exhibited very high sensitivity and specificity for acute rejection diagnosis. Conclusions: The presence of CD16+ cells inside the graft emerged as a distinct player in acute rejection, confirming other previous reports whereas we first document that in human kidney transplants, ICOS and CD26 are significantly up-regulated and both reached positive predictive values for acute rejection ≥ 80%. The other costimulatory molecules, with the exception of CD40, though widely known, did not show robust association with immune events.

The antiviral response to influenza virus is complex and multifaceted, involving many immune cell subsets. There is an urgent need to understand the role of CD4+ T cells, which orchestrate an effective antiviral response, to improve vaccine design strategies. In this study, we analyzed PBMCs from human participants immunized with influenza vaccine, using high-dimensional single-cell proteomic immune profiling by mass cytometry. Data were analyzed using a novel clustering algorithm, denoised ragged pruning, to define possible influenza virus–specific clusters of CD4+ T cells. Denoised ragged pruning identified six clusters of cells. Among these, one cluster (Cluster 3) was found to increase in abundance following stimulation with influenza virus peptide ex vivo. A separate cluster (Cluster 4) was found to expand in abundance between days 0 and 7 postvaccination, indicating that it is vaccine responsive. We examined the expression profiles of all six clusters to characterize their lineage, functionality, and possible role in the response to influenza vaccine. Clusters 3 and 4 consisted of effector memory cells, with high CD154 expression. Cluster 3 expressed cytokines like IL-2, IFN-γ, and TNF-α, whereas Cluster 4 expressed IL-17. Interestingly, some participants had low abundance of Clusters 3 and 4, whereas others had higher abundance of one of these clusters compared with the other. Taken together, we present an approach for identifying novel influenza virus–reactive CD4+ T cell subsets, a method that could help advance understanding of the immune response to influenza, predict responsiveness to vaccines, and aid in better vaccine design.

Background: In recent years, therapies with CD4+CD25highFoxP3+ regulatory T cells (Tregs) have been successfully tested in many clinical trials. The important issue regarding the use of this treatment in autoimmune conditions remains the specificity toward particular antigen, as because of epitope spread, there are usually multiple causative autoantigens to be regulated in such conditions. Methods: Here we show a method of generation of Tregs enriched with antigen-reactive clones that potentially covers the majority of such autoantigens. In our research, Tregs were expanded with anti-CD28 and anti-CD154 antibodies and autologous monocytes and loaded with a model peptide, such as whole insulin or insulin β chain peptide 9–23. The cells were then sorted into cells recognizing the presented antigen. The reactivity was verified with functional assays in which Tregs suppressed proliferation or interferon gamma production of autologous effector T cells (polyclonal and antigen-specific) used as responders challenged with the model peptide. Finally, we analyzed clonotype distribution and TRAV gene usage in the specific Tregs. Results: Altogether, the applied technique had a good yield and allowed us to obtain a Treg product enriched with a specific subset, as confirmed in the functional tests. The product consisted of many clones; nevertheless, the content of these clones was different from that found in polyclonal or unspecific Tregs. Conclusions: The presented technique might be used to generate populations of Tregs enriched with cells reactive to any given peptide, which can be used as a cellular therapy medicinal product in antigen-targeted therapies.

SummaryDecreasing graft rejection and increasing graft and patient survival are great challenges facing liver transplantation (LT). Different T cell subsets participate in the acute cellular rejection (ACR) of the allograft. Cell-mediated immunity markers of the recipient could help to understand the mechanisms underlying acute rejection. This study aimed to analyse different surface antigens on T cells in a cohort of adult liver patients undergoing LT to determine the influence on ACR using multi-parametric flow cytometry functional assay. Thirty patients were monitored at baseline and during 1 year post-transplant. Two groups were established, with (ACR) and without (NACR) acute cellular rejection. Leukocyte, total lymphocyte, percentages of CD4+CD154+ and CD8+CD154+ T cells, human leukocyte antigen (HLA) mismatch between recipient–donor and their relation with ACR as well as the acute rejection frequencies were analysed. T cells were stimulated with concanavalin A (Con-A) and surface antigens were analysed by fluorescence activated cell sorter (FACS) analysis. A high percentage of CD4+CD154+ T cells (P = 0·001) and a low percentage of CD8+CD154+ T cells (P = 0·002) at baseline were statistically significant in ACR. A receiver operating characteristic analysis determined the cut-off values capable to stratify patients at high risk of ACR with high sensitivity and specificity for CD4+CD154+ (P = 0·001) and CD8+CD154+ T cells (P = 0·002). In logistic regression analysis, CD4+CD154+, CD8+CD154+ and HLA mismatch were confirmed as independent risk factors to ACR. Post-transplant percentages of both T cell subsets were significantly higher in ACR, despite variations compared to pretransplant. These findings support the selection of candidates for LT based on the pretransplant percentages of CD4+CD154+ and CD8+CD154+ T cells in parallel with other transplant factors.

Immunological memory is a critical characteristic of a successful long-term adaptive immune response. During the initial phases of antigen:B lymphocyte interactions, B cells participate in the germinal center reaction, in which T-B cell interactions take place. CD154 on T cells acts as a ligand that binds to the CD40 receptor on B cells and facilitates the differentiation of B cells to memory B cells. However, cell fate determinants controlled by CD40 signal for cellular differentiation are unclear. In this study, we explored miRNA and miRNA-targets as cell fate determinants in CD40 signaled B cells. We selected candidate miRNAs based on their involvement in the regulation of B cell development, activation, and differentiation. We found that CD40 signal reduced transcript levels of miR150-5p, 17-5p, 146a-5p, 26a-5p and increased levels of miR292a-5p. Gene set enrichment analyses of previously submitted microarray data revealed accordant changes in levels of gene targets of these miRNA. Gene ontology analysis of miRNA-targets showed enrichment of genes participating in pathways such as DNA damage response, RNA/protein metabolism, and cell cycle regulation. Subsequently, studies on candidate miRNA-targets showed a CD40 signal driven differential regulation of Ccnd2, Pten, Traf6, c-Myb, and Btla. Further, 'gain of function' studies using mimics of the downregulated miRNAs, confirmed a predicted reduction in miRNA responsive targets; such as reduction of Ccnd2 levels in mimic treated groups of miR146a-5p, 26a-5p, and 17-5p. In conclusion, our study reveals that CD40 signal modulates levels of selected miRNAs as well as their cognate targets, whose enriched participation in diverse processes may help delineate downstream cell fate decisions.

Antagonism of the CD154/CD40 pathway is a highly effective means of inducing long-term graft survival in pre-clinical models. Using a fully allogeneic murine transplant model, we found that CD154 blockade was more effective in prolonging graft survival than was CD40 blockade, raising the possibility that CD154 binds a second receptor. To test this, we queried the impact of CD154 antagonism in the absence of CD40. Data indicated that anti-CD154 functioned to reduce graft-infiltrating CD8(+) T cells in both WT and CD40(−/−) hosts. Because it has recently been reported that CD154 can ligate CD11b, we addressed the impact of blocking CD154-CD11b interactions during transplantation. We utilized a specific peptide antagonist that prevents CD154 binding of CD11b but has no effect on CD154-CD40 interactions. CD154:CD11b antagonism significantly increased the efficacy of anti-CD40 in prolonging allograft survival as compared to anti-CD40+control peptide. Mechanistically, CD154:CD11b antagonism functioned to reduce the frequency of graft-infiltrating CD8(+) T cells and innate immune cells. These data therefore demonstrate that blocking CD154 interactions with both CD40 and CD11b is required for optimal inhibition of alloimmunity, and provide an explanation for why CD40 blockers may be less efficacious than anti-CD154 reagents for the inhibition of allograft rejection.

Background Waldenström macroglobulinemia (WM) is a subset of lymphoplasmacytic lymphoma (LPL) with bone marrow (BM) involvement and an IgM monoclonal gammopathy of any level. We aimed to identify the clinical, laboratory, and BM findings of patients with WM and to evaluate the usefulness of CD154 for the diagnosis and prognosis of WM. Methods We reviewed the medical records and BM studies and/or flow cytometric immunotyping of 31 patients with untreated WM. Semiquantitative immunohistochemistry (CD20, CD138, tryptase, and CD154) of BM was performed. Results Only six patients presented with symptoms of hyperviscosity syndrome. Eleven patients had solid cancer and/or another hematologic malignancy. Mast cells (MC) increased in all samples, with some in close contact with tumor cells. Tryptase-positive MC (17.1/ high-power fields [HPF], 1.2–72.0/HPF) and CD154-positive MC (8.6/HPF, 0.1–31.1/HPF) were observed. The high CD154-positive MC (≥8.6/HPF) group showed a lower overall five-year survival rate than the low CD154-positive MC (

Summary CD40 and its ligand CD40L (CD154) belong to the tumor necrosis factor receptor superfamily and are expressed by a variety of immune and non-immune cells. CD40L plays a central role in co-stimulation and regulation of the immune response via activation of cells expressing CD40. Imbalance of the CD40–CD40L co-stimulatory pathway has been reported in many autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and Sjogren's syndrome, thus supporting its role in the breach of immune tolerance that is typical of these diseases. Targeting CD40–CD40L signalling might represent a novel therapeutic option for several autoimmune disorders.

Although CD4+ CD45RA- Foxp3l ° cytokine-secreting T cells (Fr.III cells) have been reported to be increased in systemic lupus erythematosus (SLE), their function and effects on response of B cells are still unclear. Here, we dissect how BACH2 regulates Fr.III cells function and promotes B-cell response in active SLE patients. We measured cytokines and BACH2 expression, and found that Fr.III cells from SLE patients produce much more inflammatory cytokines and were more able to promote B- cell proliferation, IgG, IgA, and TNF-α production than controls in a co-culture system. Fr.III cells expressed high levels of ICOS and CD154, but a low level of Tfr and BACH2, BACH2 expression was negatively correlated with SLE Disease Activity Index. Overexpressed of BACH2 in Fr.III cells, decreased cytokines expression and reduced B-cell response. Furthermore, we identified a reduction of H3K27ac level binding at the BACH2 locus in the SLE Fr.III cells and SLE serum stimulation decreased H3K27ac binding at the BACH2 locus, which could be restored using trichostatin A (TSA). In conclusion, BACH2 was associated with SLE disease activity, regulated the function of Fr.III cells, and promoted B-cells response. Targeting BACH2 may be a new immune intervention therapy of SLE.

Objective CD4+CD8+ double-positive T-cells (DPTs) have been classified as a separate T-cell subpopulation, with two main phenotypes: CD4high CD8low and CD4low CD8high. In recent years, the relevance of DPTs in the pathogenesis of infections, tumors, and autoimmune diseases has been recognized. Reference values among healthy individuals remain unknown. Therefore, the aim of this study is to provide a reference value for DPTs in peripheral blood from healthy donors in a blood bank in Bogota, Colombia, and to determine the activation status using a surface marker. Materials and methods One hundred healthy donors were enrolled in the study. Peripheral blood cells were stained for CD3, CD4, CD8, and CD154 (CD40L), and cellular viability was assessed with 7-aminoactinomycin D and analyzed by flow cytometry. Results The median value for DPTs was 2.6% (interquartile range=1.70%-3.67%). Women had higher percentages of DPTs than men (3.3% vs. 2.1%). The subpopulation of CD4low CD8high showed higher expression of CD154 than the other T-cell subpopulations. Conclusion DPT reference values were obtained from blood bank donors. A sex difference was found, and the CD4low CD8high subpopulation had the highest activation marker expression.

Tick-borne encephalitis (TBE) is a viral infection of the CNS caused by TBE virus. With no specific treatment available, the only protection is a formalin-inactivated whole virus vaccine. Primary immunization with European TBE vaccines, as recommended by the manufacturers, consists of three vaccine doses administered within a 1-y period. Protection from vaccination is believed to be mediated by Abs, yet T cells may also have a protective role. We set out to characterize the human CD4+ T cell response throughout primary TBE immunization. The responses were evaluated before vaccination and 1 mo after each vaccine dose. A heterogeneous magnitude of CD4+ T cell–mediated memory responses was observed in regard to lymphoblast expansion and cytokine production (IFN-γ, IL-2, and TNF), with the highest median magnitude detected after the second dose of vaccine. Stimulation with an overlapping peptide library based on structural TBE virus proteins E and C revealed that CD4+ T cells concomitantly producing IL-2 and TNF dominated the responses from vaccinees after each vaccine dose, whereas a control cohort of TBE patients responded mainly with all three cytokines. CD107a expression was not upregulated upon peptide stimulation in the vaccinees. However, CD154 (CD40L) expression on cytokine-positive memory CD4+ T cells significantly increased after the second vaccine dose. Taken together, TBE vaccination induced CD4+ T cell responses dominated by IL-2 and TNF production together with CD154 upregulation and a lower IFN-γ response compared with TBE patients. This response pattern was consistent after all three doses of TBE vaccine.

BackgroundOral immunotherapy (OIT) is an emerging treatment for cow’s milk protein (CMP) allergy in children. The mechanisms driving tolerance following OIT are not well understood. Regulatory T cells (TREG) cells are key inhibitors of allergic responses and promoters of allergen-specific tolerance. In an exploratory study, we sought to detect induction of allergen-specific TREG in a cohort of subjects undergoing OIT.MethodsPediatric patients with a history of allergic reaction to cow’s milk and a positive Skin Pick Test (SPT) and/or CMP-specific IgE >0.35 kU, as well as a positive oral challenge to CMP underwent OIT with escalating doses of milk and were followed for up to 6 months. At specific milestones during the dose escalation and maintenance phases, casein-specific CD4+ T cells were expanded from patient blood by culturing unfractionated PBMCs with casein in vitro. The CD4+ T cell phenotypes were quantified by flow cytometry.ResultsOur culture system induced activated casein-specific FOXP3+Helios+ TREG cells and FOXP3- TEFF cells, discriminated by expression of CD137 (4-1BB) and CD154 (CD40L) respectively. The frequency of casein-specific TREG cells increased significantly with escalating doses of milk during OIT while casein-specific TEFF cell frequencies remained constant. Moreover, expanded casein-specific TREG cells expressed higher levels of FOXP3 compared to polyclonal TREG cells, suggesting a more robust TREG phenotype. The induction of casein-specific TREG cells increased with successful CMP desensitization and correlated with increased frequencies of casein-specific Th1 cells among OIT subjects. The level of casein-specific TREG cells negatively correlated with the time required to reach the maintenance phase of desensitization.ConclusionsOverall, effective CMP-OIT successfully promoted the expansion of casein-specific, functionally-stable FOXP3+ TREG cells while mitigating Th2 responses in children receiving OIT. Our exploratory study proposes that an in vitro TREG response to casein may correlate with the time to reach maintenance in CMP-OIT.

Human islet antigen reactive CD4+ memory T cells (IAR T cells) play a key role in the pathogenesis of autoimmune type 1 diabetes (T1D). Using single-cell RNA sequencing (scRNA-Seq) to identify T cell receptors (TCRs) in IAR T cells, we have identified a class of TCRs that share TCRα chains between individuals ("public" chains). We isolated IAR T cells from blood of healthy, new-onset T1D and established T1D donors using multiplexed CD154 enrichment and identified paired TCRαβ sequences from 2767 individual cells. More than a quarter of cells shared TCR junctions between 2 or more cells ("expanded"), and 29/47 (~62%) of expanded TCRs tested showed specificity for islet antigen epitopes. Public TCRs sharing TCRα junctions were most prominent in new-onset T1D. Public TCR sequences were more germline like than expanded unique, or "private," TCRs, and had shorter junction sequences, suggestive of fewer random nucleotide insertions. Public TCRα junctions were often paired with mismatched TCRβ junctions in TCRs; remarkably, a subset of these TCRs exhibited cross-reactivity toward distinct islet antigen peptides. Our findings demonstrate a prevalent population of IAR T cells with diverse specificities determined by TCRs with restricted TCRα junctions and germline-constrained antigen recognition properties. Since these "innate-like" TCRs differ from previously described immunodominant TCRβ chains in autoimmunity, they have implications for fundamental studies of disease mechanisms. Self-reactive restricted TCRα chains and their associated epitopes should be considered in fundamental and translational investigations of TCRs in T1D.

The interaction between CD40 and CD154 (CD40 ligand) is central in immunology, participating in CD4+ T cell priming by dendritic cells (DC), CD4+ T cell help to B cells and classical macrophage activation by CD4+ T cells. However, its role in the Th2 side of immunology including helminth infection remains incompletely understood. Contrary to viral and bacterial stimuli, helminth products usually do not cause CD40 up-regulation in DC, and exogenous CD40 ligation drives Th2-biased systems towards Th1. On the other hand, CD40 and CD154 are necessary for induction of most Th2 responses. We attempt to reconcile these observations, mainly by proposing that (i) CD40 up-regulation in DC in Th2 systems is mostly induced by alarmins, (ii) the Th2 to Th1 shift induced by exogenous CD40 ligation is related to the capacity of such ligation to enhance IL-12 production by myeloid cells, and (iii) signals elicited by endogenous CD154 available in Th2 contexts and by exogenous CD40 ligation are probably different. We stress that CD40-CD154 is important beyond cognate cellular interactions. In such a context, we argue that the proliferation response of B-cells to IL-4 plus CD154 reflects a Th2-specific mechanism for polyclonal B-cell amplification and IgE production at infection sites. Finally, we argue that CD154 is a general immune activation signal across immune polarization including Th2, and propose that competition for CD154 at tissue sites may provide negative feedback on response induction at each site.

Pig organ xenotransplantation offers a solution to the shortage of deceased human organs for transplantation. The pathobiological response to a pig xenograft is complex, involving antibody, complement, coagulation, inflammatory, and cellular responses. To overcome these barriers, genetic manipulation of the organ-source pigs has largely been directed to two major aims – (i) deletion of expression of the known carbohydrate xenoantigens against which humans have natural (preformed) antibodies, and (ii) transgenic expression of human protective proteins, e.g., complement- and coagulation-regulatory proteins. Conventional (FDA-approved) immunosuppressive therapy is unsuccessful in preventing an adaptive immune response to pig cells, but blockade of the CD40:CD154 costimulation pathway is successful. Survival of genetically-engineered pig kidneys in immunosuppressed nonhuman primates can now be measured in months. Non-immunological aspects, e.g., pig renal function, a hypovolemia syndrome, and rapid growth of the pig kidney after transplantation, are briefly discussed. We suggest that patients on the wait-list for a deceased human kidney graft who are unlikely to receive one due to long waiting times are those for whom kidney xenotransplantation might first be considered. The potential risk of infection, public attitudes to xenotransplantation, and ethical, regulatory, and financial aspects are briefly addressed.

Food allergy affects an estimated 8% of children in the US, with increasing severity and global prevalence1. Oral immunotherapy (OIT) is a recently approved treatment with outcomes ranging from sustained tolerance to food allergen to no apparent benefit2,3. The immunological underpinnings that influence clinical outcomes of OIT still remain largely unresolved. Using single-cell RNA sequencing and paired TCRα/β sequencing, we assessed the transcriptomes of CD154+ and CD137+ peanut-reactive T helper cells from 12 peanut-allergic patients longitudinally throughout OIT. We observed expanded populations of cells expressing Th1, Th2, and Th17 signatures that further separated into six clonally distinct subsets, including a Tfh1-like, a Tfh2-like, a Th2A-like, and a Th2reg-like subset. Four of these subsets demonstrated convergence of TCR sequences, suggesting antigen-driven T cell fate. Although we observed suppression during OIT of Th2 and Th1 gene signatures within effector clonotypes, Tfh clonotypes were unaffected. We also did not observe significant clonal deletion or induction among the antigen-reactive T cells characterized. Positive outcomes were associated with larger decrease of Th2 signatures in Th2A-like cells, while treatment failure was associated with high baseline inflammatory gene signatures that were unmodulated by OIT. These signatures, including expression of OX40, OX40L, STAT1, and GPR15, were most clearly present in Th1 and Th17 clonotypes, but were also more broadly detected across the CD154+ CD4 population. These results demonstrate that differential clinical response is associated both with pre-existing trait characteristics of the CD4 immune compartment and with susceptibility to modulation by OIT.Conflict of Interest StatementA.A.T., T.M.G., J.C.L., and the Massachusetts Institute of Technology have filed patents related to the single-cell sequencing methods used in this work. J.C.L. has interests in Sunflower Therapeutics PBC, Pfizer, Honeycomb Biotechnologies, OneCyte Biotechnologies, SQZ Biotechnologies, Alloy Therapeutics, QuantumCyte, Amgen, and Repligen. J.C.L.’s interests are reviewed and managed under Massachusetts Institute of Technology’s policies for potential conflicts of interest. J.C.L. receives sponsored research support at MIT from Amgen, the Bill & Melinda Gates Foundation, Biogen, Pfizer, Roche, Takeda, and Sanofi. The spouse of J.C.L. is an employee of Sunflower Therapeutics PBC. T.M.G. is currently an employee of Honeycomb Biotechnologies, Inc. A.A.T. is currently an employee of Immunitas Therapeutics, Inc. W.G.S. is a consultant of Aimmune Therapeutics.

We developed this comprehensive 28-color flow cytometry panel with the aim to measure a variety of T cell effector functions in combination with T cell differentiation markers (CCR7, CD27, CD28, CD45RO, CD95) in γδ T cells and CD4+ and CD8+ αβ T cells (Table 1). The effector functions measured in this panel include activation and co-stimulatory molecules (CD69, CD137, and CD154), cytokines (IL-2, IL-13, IL-17A, IL-21, IL-22, TNF, and IFNγ), the chemokine IL-8, cytotoxic molecules (perforin and granzyme B), and the degranulation marker CD107a. In addition, Ki67 enables the identification and analysis of recently activated T cells. To characterize regulatory T cells (Tregs ), we included CD25, CD39, and the canonical Tregs transcription factor FoxP3. We developed and optimized this panel for cryopreserved human peripheral blood mononuclear cells (PBMC) and stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. However, we successfully tested other types of stimulation such as staphylococcus enterotoxin B (SEB) or a mix of immunodominant peptides (CEF peptide pool) from cytomegalovirus (CMV), Epstein-Barr virus (EBV) and influenza. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

ObjectiveTo examine the role of CD40–CD154 costimulation and effects of therapeutic pathway blockade in the non-obese diabetic (NOD/ShiLtJ) model of Sjögren’s syndrome (SS).MethodsWe assessed leucocyte infiltration in salivary glands (SGs) from NOD/ShiLtJ mice by immunohistochemistry and examined transcriptomics data of SG tissue from these animals for evidence of a CD40 pathway gene signature. Additionally, we dosed MR1 (anti-CD154 antibody) in NOD mice after the onset of SS-like disease and examined the effects of MR1 treatment on sialadenitis, autoantibody production, SG leucocyte infiltration, gene expression downstream of CD40 and acquaporin 5 (AQP5) expression.ResultsWe could detect evidence of CD40 expression and pathway activation in SG tissue from NOD mice. Additionally, therapeutic treatment with MR1 suppressed CD40 pathway genes and sialadenitis, inhibited ectopic lymphoid structure formation and autoantibody production, as well as decreased the frequency of antibody-secreting cells in SGs but had minimal effects on AQP5 expression in NOD/ShiLtJ SGs.ConclusionCD40–CD154 interactions play an important role in key pathological processes in a mouse model of SS, suggesting that blockade of this costimulatory pathway in the clinic may have beneficial therapeutic effects in patients suffering from this autoimmune exocrinopathy.

Costimulation is a critical step in T-cell activation, and costimulatory blockade at the time of T cell activation leads to T-cell anergy and allograft tolerance in animal models of transplantation. CD28:B7 is the most important costimulatory pathway and the balance of signals between CD28 and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) is a central determinant of transplant outcome. Form a clinical standpoint, CTLA-4 Ig is the only approved agent for costimulation blockade in transplantation. Advantages and disadvantages of its use are discussed. Progress in developing novel agents to target other pathways, including the promising CD40:CD154 pathway, is also discussed.

Thrombocytes keep a leading role in conjugating thrombosis, inflammation and congenital immune responses. The platelets provide stable adhesion and interaction with immune cells. Activated platelets express CD40L (CD154), a membrane glycoprotein of tumor necrosis factor (TNF) family. Hence, the platelets are the main source of sCD40L in blood plasma. Platelet CD154 may interact with CD40 receptor on endothelial cells, causing an inflammatory response, and enhancing production of immunoglobulins by B-lymphocytes. Membrane and soluble CD154 of platelets combined with other signals can induce maturation and activation of dendritic cells (DC). The platelets possess functional receptors, e.g., TLR2, TLR4, TLR7 and TLR9 they also bear Fc-receptors, including FcγRIIA, FcεRI and FcαRIA. FcγRIIA on platelets mediate protection against bacteria. Cross-linking of FcαRI on platelets results in production of prothrombotic and pro-inflammatory mediators such as tissue factor and IL-1β. Activation of platelets via FcεR1 causes release of chemokine RANTES and serotonin, which contribute to the pro-inflammatory response of other immune cells. Platelets possess receptors for activated complement components and its fragments (CR2, CR3, CR4, C1q, C1 inhibitor and factors D and H). Activated platelets trigger the complement system through the release of protein kinases and ATP, and also by phosphorylation of C3 and C3b. α-granules of platelets contain chemokines which represent the most numerous group of antimicrobial proteins of platelets (kinocidins), and there is an antimicrobial protein of the defensin family – hBD-1 in the cytoplasm of platelets. Ligand and receptor of the TNF superfamily (TRAIL and LIGHT), the SDF-1 chemokine (CXCL12), the IL-1βinterleukins, IL-8 and the soluble IL-6 receptor (sRIL-6) are recognized as platelet products belonging to the family of cytokines and their receptors. The HMGB-1 protein classified as an inflammatory cytokine, is expressed by activated platelets and causes formation of the extracellular traps by neutrophils. Platelets produce numerous growth factors, including EGF-α and EGF-β1, EGF-β2, TGF-α and TGF-β1, TGF-β2, PDGF, HGF, FGF-β, IGF, pro- and antiangiogenic factors, e.g., VEGF-F and angiopoietins Ang-1 and Ang-2. Fulfillment of immune functions by the platelets is carried out by their interaction with leukocytes, which are attracted to the site of infection and inflammation and retained during the development of an “immune thrombus” under conditions of high shear stress. Platelets can not only maintain and guide the immune response, but also initiate these events. They are able to present the antigen in the context of MHC class I molecules, and activate naїve CD8+T lymphocytes. Potential consequences of platelet interaction with neutrophils, monocytes, dendritic cells and lymphocytes are discussed in the review article.

The T follicular helper (Tfh) cell subset of CD4+ Th cells promotes affinity maturation by B cells in germinal centers. The contribution of other Th cell subsets to B cell responses has not been fully explored in vivo. We addressed this issue by analyzing the T cell–dependent B cell response to the protein Ag PE in mice lacking specific Th cell subsets. As expected, PE-specific germinal center B cell production required Tfh cells. However, Tfh, Th1, or Th17 cell–deficient mice produced as many PE-specific, isotype-switched plasmablasts as wild-type mice. This response depended on Th cell expression of CD154 and Ag presentation by B cells. These results indicate that many Th cell subsets can promote plasmablast formation by providing CD40 signals to naive B cells.

Currently, no data are available regarding the expression levels of CD40L on CD4+ T cells in patients with neuromyelitis optica spectrum disorders (NMOSD). The percentage of circulating CD40L+CD4+ T cells was measured by flow cytometry in 23 NMOSD patients and 10 healthy controls. The ratio of CD40L+CD4+ to CD4+ T cells in patients at acute phase (18.28 ± 15.56%) was significantly higher than that in healthy controls (7.23 ± 5.94%, P = .032) and was positively correlated with disease severity (r = 0.532, P = .041). Thus, our results suggest an important role of this molecule in acute attacks of NMOSD.

CD40 receptor is expressed on B lymphocytes and other professional antigen-presenting cells. The binding of CD40 to its ligand CD154 on the surface of T helper cells plays an important role in the activation of B lymphocytes required for production of antibodies, in particular, against autoantigens. Association of several single nucleotide polymorphisms (SNPs) located in the non-coding areas of human CD40 locus with the elevated risk of autoimmune diseases has been demonstrated. The most studied of these SNPs is rs4810485 located in the first intron of the CD40 gene. Expression of the CD40 gene in B lymphocytes of donors homozygous for the common allelic variant of this polymorphism (G) is higher than in B cells from donors carrying the minor (T) variant. We investigated the enhancer activity of this fragment of the CD40 locus in human B cell lines and showed that it is independent on the rs4810485 alleles. However, the minor allelic variants of the rs4810485-linked SNPs rs548231435 and rs115662534 were associated with a significant decrease in the activity of the CD40 promoter due to the impairments in the binding of EBF1 and STAT1 transcription factors, respectively.

Vaccines against SARS-CoV-2 have shown high efficacy in clinical trials, yet a full immunologic characterization of these vaccines, particularly within the upper respiratory tract, remains lacking. We enumerated and phenotyped T cells in nasal mucosa and blood before and after vaccination with the Pfizer-BioNTech COVID-19 vaccine (n =21). Tissue-resident memory (Trm) CD8+ T cells expressing CD69+CD103+ expanded ∼12 days following the first and second doses, by 0.31 and 0.43 log10cells per swab respectively (p=0.058 and p=0.009 in adjusted linear mixed models). CD69+CD103+CD8+ T cells in the blood decreased post-vaccination. Similar increases in nasal CD8+CD69+CD103-T cells were observed, particularly following the second dose. CD4+ Th17 cells were also increased in abundance following both doses. Following stimulation with SARS-CoV-2 spike peptides, CD8+ T cells increased expression of CD107a and CD154. These data suggest that nasal T cells may be induced and contribute to the protective immunity afforded by this vaccine.

Assessment of T-cell immunity to the COVID-19 coronavirus requires reliable assays and is of great interest, given the uncertain longevity of the antibody response. Some recent reports have used immunodominant spike (S) antigenic peptides and anti-CD28 co-stimulation in varying combinations to assess T-cell immunity to SARS-CoV-2. These assays may cause T-cell hyperstimulation and could overestimate antiviral immunity in chronically immunosuppressed transplant recipients, who are predisposed to infections and vaccination failures. Here, we evaluate CD154-expressing T-cells induced by unselected S antigenic peptides in 204 subjects-103 COVID-19 patients and 101 healthy unexposed subjects. Subjects included 72 transplanted and 130 non-transplanted subjects. S-reactive CD154+T-cells co-express and can thus substitute for IFNγ (n=3). Assay reproducibility in a variety of conditions was acceptable with coefficient of variation of 2-10.6%. S-reactive CD154+T-cell frequencies were a) higher in 42 healthy unexposed transplant recipients who were sampled pre-pandemic, compared with 59 healthy non-transplanted subjects (p=0.02), b) lower in Tr COVID-19 patients compared with healthy transplant patients (p

Food allergy affects an estimated 8% of children in the United States. Oral immunotherapy (OIT) is a recently approved treatment, with outcomes ranging from sustained tolerance to food allergens to no apparent benefit. The immunological underpinnings that influence clinical outcomes of OIT remain largely unresolved. Using single-cell RNA-Seq and paired T cell receptor α/β (TCRα/β) sequencing, we assessed the transcriptomes of CD154+ and CD137+ peanut-reactive T helper (Th) cells from 12 patients with peanut allergy longitudinally throughout OIT. We observed expanded populations of cells expressing Th1, Th2, and Th17 signatures that further separated into 6 clonally distinct subsets. Four of these subsets demonstrated a convergence of TCR sequences, suggesting antigen-driven T cell fates. Over the course of OIT, we observed suppression of Th2 and Th1 gene signatures in effector clonotypes but not T follicular helper-like (Tfh-like) clonotypes. Positive outcomes were associated with stronger suppression of Th2 signatures in Th2A-like cells, while treatment failure was associated with the expression of baseline inflammatory gene signatures that were present in Th1 and Th17 cell populations and unmodulated by OIT. These results demonstrate that differential clinical responses to OIT are associated with both preexisting characteristics of peanut-reactive CD4+ T cells and suppression of a subset of Th2 cells.

B cell activation by Tfh cells, i.e., through CD154 engagement of CD40 and IL-21, and survival within GCs are crucial for the T-dependent Ab response. LUBAC, composed of HOIP, SHARPIN, and HOIL-1, catalyzes linear ubiquitination (Linear M1-Ub) to mediate NF-κB activation and cell survival induced by TNF receptor superfamily members, which include CD40. As shown in this study, B cells expressing the Sharpin null mutation cpdm (Sharpincpdm) could undergo proliferation, CSR, and SHM in response to immunization by a T-dependent Ag, but were defective in survival within GCs, enrichment of a mutation enhancing the BCR affinity, and production of specific Abs. Sharpincpdm B cells stimulated in vitro with CD154 displayed normal proliferation and differentiation, marginally impaired NF-κB activation and survival, but markedly exacerbated death triggered by IL-21. While activating the mitochondria-dependent apoptosis pathway in both Sharpin+/+ and Sharpincpdm B cells, IL-21 induced Sharpincpdm B cells to undergo sustained activation of caspase 9 and caspase 8 of the mitochondria-dependent and independent pathway, respectively, and ultimately caspase 3 in effecting apoptosis. These were associated with loss of the caspase 8 inhibitor cFLIP and reduction in cFLIP Linear M1-Ub, which interferes with cFLIP poly-ubiquitination at Lys48 and degradation. Finally, the viability of Sharpincpdm B cells was rescued by caspase inhibitors but virtually abrogated – together with Linear M1-Ub and cFLIP levels – by a small molecule HOIP inhibitor. Thus, LUBAC controls the cFLIP expression and inhibits the effects of caspase 8 and IL-21-activated caspase 9, thereby suppressing apoptosis of CD40 and IL-21-activated B cells and promoting GC B cell survival.

There is evidence that berberine (BBR), a clinically relevant plant compound, ameliorates clinically apparent collagen-induced arthritis (CIA) in vivo. However, to date, there are no studies involving the use of BBR which explore its prophylactic potential in this model of rheumatoid arthritis (RA). The aim of this study was to determine if prophylactic BBR use during the preclinical phase of collagen-induced arthritis would delay arthritic symptom onset, and to characterize the cellular mechanism underlying such an effect. DBA/1J mice were injected with an emulsion of bovine type II collagen (CII) and complete Freund’s adjuvant (day 0) and a booster injection of CII in incomplete Freund’s adjuvant (day 18) to induce arthritis. Mice were then given i.p. injections of 1 mg/kg/day of BBR or PBS (vehicle with 0.01% DMSO) from days 0 to 28, were left untreated (CIA control), or were in a non-arthritic control group (n = 15 per group). Incidence of arthritis in BBR-treated mice was 50%, compared to 90% in both the CIA and PBS controls. Populations of B and T cells from the spleens and draining lymph nodes of mice were examined on day 14 (n = 5 per group) and day 28 (n = 10 per group). BBR-treated mice had significantly reduced populations of CD4+Th and CD4+CXCR5+ Tfh cells, and an increased proportion of Foxp3+ Treg at days 14 and 28, as well as reduced expression of co-stimulatory molecules CD28 and CD154 at both endpoints. The effect seen on T cell populations and co-stimulatory molecule expression in BBR-treated mice was not mirrored in CD19+ B cells. Additionally, BBR-treated mice experienced reduced anti-CII IgG2a and anti-CII total IgG serum concentrations. These results indicate a potential role for BBR as a prophylactic supplement for RA, and that its effect may be mediated specifically through T cell suppression. However, the cellular effector involved raises concern for BBR prophylactic use in the context of vaccine efficacy and other primary adaptive immune responses.

Clinical presentations of dengue fever (DF) are diverse and non-specific, causing unpredictable progression and outcomes. Its progression and severity have been associated with cytokine levels alteration. In this study, dengue patients were classified into groups following the 2009 WHO dengue classification scheme to investigate the cytokine signature at different severity of the disease: dengue without warning sign symptoms (A), dengue with warning signs (B), severe dengue (C), other fever (OF) and healthy (Healthy). We analyzed 23 different cytokines simultaneously, namely IL-1b, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-17A, IL-33, CD14, CD54, CD62E, CD62L, CD62p, CD106, CD121b, CD154, CD178, GM-CSF, IFN-g, MIF, ST2 and TNF from patients admitted to National Cheng Kung University Hospital during the 2015 Taiwan dengue outbreak. Cytokines TNF, CD54, CD62E, CD62L, CD62P, GM-CSF, IL-1b, IL-2, IL-6, IL-8, IL-10, IL-12p70, IL-17A, INF-g and MIF were elevated while CD106, CD154, IL-4 and L-33 were decreased when compared to the control. IL-10 demonstrated to be a potential diagnostic marker for DF (H and A group, AUC = 0.944, H and OF group, AUC = 0.969). CD121b demonstrated to be predictive of the SD (A and B group, AUC = 0.744, B and C group, AUC = 0.775). Our results demonstrate the cytokine profile changes during the progression of dengue and highlight possible biomarkers for optimizing effective intervention strategies.