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Maintenance of peripheral tolerance by CD4+Foxp3+ regulatory T cells (Tregs) is essential for regulating autoreactive T cells. The loss of function of Foxp3 leads to autoimmune disease in both animals and humans. An example is the rare, X-linked recessive disorder known as IPEX (Immune Dysregulation, Polyendocrinopathy, Enteropathy X-linked) syndrome. In more common human autoimmune diseases, defects in Treg function are accompanied with aberrant effector cytokines such as IFNγ. It has recently become appreciated that Tregs plays an important role in not only maintaining immune homeostasis but also in establishing the tissue microenvironment and homeostasis of non-lymphoid tissues. Tissue resident Tregs show profiles that are unique to their local environments which are composed of both immune and non-immune cells. Core tissue-residence gene signatures are shared across different tissue Tregs and are crucial to homeostatic regulation and maintaining the tissue Treg pool in a steady state. Through interaction with immunocytes and non-immunocytes, tissue Tregs exert a suppressive function via conventional ways involving contact dependent and independent processes. In addition, tissue resident Tregs communicate with other tissue resident cells which allows Tregs to adopt to their local microenvironment. These bidirectional interactions are dependent on the specific tissue environment. Here, we summarize the recent advancements of tissue Treg studies in both human and mice, and discuss the molecular mechanisms that maintain tissue homeostasis and prevent pathogenesis.

Genome-wide association studies (GWAS) have identified genetic susceptibility loci for a variety of autoimmune and inflammatory diseases. These studies confirm the fundamental genetic basis of individual autoimmune diseases, and also point to shared etiological mechanisms across the spectrum of autoimmunity. While hundreds of genetic loci have been implicated in autoimmune diseases, the translation of individual susceptibility loci into specific molecular mechanisms for individual diseases remains difficult. This review highlights recent advances in the genetics of autoimmune disease, and the emerging use of epigenetic techniques to identify pathogenic cell types and causal molecular mechanisms of autoimmunity.

The T cell receptor (TCR) endows T cells with antigen specificity and is central to nearly all aspects of T cell function. Each naïve T cell has a unique TCR sequence that is stably maintained during cell division. In this way, the TCR serves as a molecular barcode that tracks processes such as migration, differentiation, and proliferation of T cells. Recent technological advances have enabled sequencing of the TCR from single cells alongside deep molecular phenotypes on an unprecedented scale. In this review, we discuss strengths and limitations of TCR sequences as molecular barcodes and their application to study immune responses following Programmed Death-1 (PD-1) blockade in cancer. Additionally, we consider applications of TCR data beyond use as a barcode.

Immune checkpoint blockade has demonstrated success in treating cancer but can lead to immune-related adverse events (irAEs), illustrating the centrality of these pathways in tolerance. Here, we describe programmed cell death protein 1 (PD-1) control of T cell responses, focusing on its unique restraint of regulatory T cell function. We examine successes and limitations of checkpoint blockade immunotherapy and review clinical and mechanistic features of irAEs. Last, we discuss strategies to modulate PD-1 blockade to enhance antitumor immunity while limiting autoimmunity.

Recent work both in vitro and in in vivo animal models has implicated sodium as one of a number of environmental factors in the induction of autoimmune disease, although direct experimental evidence in patients was lacking (1, 2). In PNAS, Huhn et al. (3) find that male patients with multiple sclerosis (MS) and mice with experimental autoimmune encephalitis (EAE) have elevated skin sodium deposition relative to healthy controls, as measured by sodium MRI (23Na-MRI). By quantitatively demonstrating disease-specific elevations in tissue salt stores, they establish the biological relevance of salt as an environmental risk factor for autoimmunity and the utility of 23Na-MRI for studying this phenomenon in vivo. There has been a marked increase in the incidence of autoimmune diseases in the last half-century. While the underlying genetic basis of this class of diseases has recently been elucidated implicating predominantly immune response genes (4, 5), changes in environmental factors must ultimately be driving this increase (Fig. 1). We and others have recently demonstrated that higher but physiologic salt conditions activate the p38/MAPK pathway involving NFAT5 and the serum- and glucocorticoid-inducible kinase 1 (SGK1) during cytokine-induced Th17 polarization (1, 2). Gene silencing or chemical inhibition of p38/MAPK, NFAT5, or SGK1 abrogated the high-salt–induced Th17 cell development. In animal models, high-salt diets caused mice to develop more severe EAE (1, 2) Fig. 1. MS, as with all autoimmune diseases, results from a bad outcome of gene–environmental interactions. Over 233 genetic variants have been identified that interact with environmental triggers including smoking, vitamin D, Epstein–Barr virus, and now as shown here salt that influence immune anatomic niches including the gut, adipose tissue, meninges, and skin that leads to the activation of myelin reactive T cells that initiate MS. It was also … [↵][1]1To whom correspondence may be addressed. Email: david.hafler{at}yale.edu. [1]: #xref-corresp-1-1

Background Autoimmune disease prevention requires tools to assess an individual's risk of developing a specific disease. One tool is disease-associated autoantibodies, which accumulate in an asymptomatic preclinical period. However, patients sometimes exhibit autoantibodies associated with a different disease classification. When and how these alternative autoantibodies first appear remain unknown. This cross-sectional study characterizes alternative autoimmunity, and associated genetic and environmental factors, in unaffected first-degree relatives (FDRs) of patients, who exhibit increased future risk for the same disease. Methods Samples (n = 1321) from disease-specific autoantibody-positive (aAb+) systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and type 1 diabetes (T1D) patients; and unaffected aAb+ and autoantibody-negative (aAb–) SLE and RA FDRs were tested for SLE, RA, and T1D aAbs, as well as anti-tissue transglutaminase, anti-cardiolipin and anti-thyroperoxidase. FDR SLE and RA genetic risk scores (GRS) were calculated. Findings Alternative autoimmunity occurred in SLE patients (56%) and FDRs (57·4%), RA patients (32·6%) and FDRs (34·8%), and T1D patients (43%). Expanded autoimmunity, defined as autoantibodies spanning at least two other diseases, occurred in 18·5% of SLE patients, 16·4% of SLE FDRs, 7·8% of RA patients, 5·3% of RA FDRs, and 10·8% of T1D patients. SLE FDRs were more likely to have alternative (odds ratio [OR] 2·44) and expanded (OR 3·27) autoimmunity than RA FDRs. Alternative and expanded autoimmunity were associated with several environmental exposures. Alternative autoimmunity was associated with a higher RA GRS in RA FDRs (OR 1·41), and a higher SLE GRS in aAb+ RA FDRs (OR 1·87), but not in SLE FDRs. Interpretation Autoimmunity commonly crosses disease-specific boundaries in systemic (RA, SLE) and organ-specific (T1D) autoimmune diseases. Alternative autoimmunity is more common in SLE FDRs than RA FDRs, and is influenced by genetic and environmental factors. These findings have substantial implications for preclinical disease pathogenesis and autoimmune disease prevention studies. Fund NIH U01AI101981, R01AR051394, U19AI082714, P30AR053483, P30GM103510, U54GM104938, U01AI101934, R01AI024717, U01AI130830, I01BX001834, & U01HG008666.

Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening post-infectious complication occurring unpredictably weeks after mild or asymptomatic SARS-CoV-2 infection. We profiled MIS-C, adult COVID-19, and healthy pediatric and adult individuals using single-cell RNA sequencing, flow cytometry, antigen receptor repertoire analysis, and unbiased serum proteomics, which collectively identified a signature in MIS-C patients that correlated with disease severity. Despite having no evidence of active infection, MIS-C patients had elevated S100A-family alarmins and decreased antigen presentation signatures, indicative of myeloid dysfunction. MIS-C patients showed elevated expression of cytotoxicity genes in NK and CD8+ T cells and expansion of specific IgG-expressing plasmablasts. Clinically severe MIS-C patients displayed skewed memory T cell TCR repertoires and autoimmunity characterized by endothelium-reactive IgG. The alarmin, cytotoxicity, TCR repertoire, and plasmablast signatures we defined have potential for application in the clinic to better diagnose and potentially predict disease severity early in the course of MIS-C., Graphical abstract, Multisystem inflammatory syndrome in children (MIS-C) is a life-threatening and unpredictable condition of unknown etiology. Ramaswamy et al. use peripheral blood single-cell transcriptomic profiling along with other techniques to define key innate and adaptive signatures that characterize MIS-C.

SummaryA dysregulated immune response against coronavirus-2 (SARS-CoV-2) plays a critical role in the outcome of patients with coronavirus disease 2019 (COVID-19). A significant increase in circulating plasmablasts is characteristic of COVID-19 though the underlying mechanisms and its prognostic implications are not known. Here, we demonstrate that in the acute phase of COVID-19, activated PD-1highCXCR5−CD4+ T cells, peripheral helper T cells, (Tph) are significantly increased and promote inflammatory tissue-homing plasmablasts in patients with stable but not severe COVID-19. Analysis of scRNA-seq data revealed that plasmablasts in stable patients express higher levels of tissue-homing receptors including CXCR3. The increased Tph cells exhibited “B cell help” signatures similar to that of circulating T follicular helper (cTfh) cells and promoted B cell differentiation in vitro. Compared with cTfh cells, Tph cells produced more IFNγ, inducing tissue-homing chemokine receptors on plasmablasts. Finally, expansion of activated Tph cells was correlated with the frequency of CXCR3+ plasmablasts in the acute phase of patients with stable disease. Our results demonstrate a novel role for Tph cells in acute viral immunity by inducing ectopic, antibody secreting plasmablasts.

Protective immunity against COVID-19 likely depends on the production of SARS-CoV-2–specific plasma cells and memory B cells postinfection or postvaccination. Previous work has found that germinal center reactions are disrupted in severe COVID-19. This may adversely affect long-term immunity against reinfection. Consistent with an extrafollicular B cell response, patients with severe COVID-19 have elevated frequencies of clonally expanded, class-switched, unmutated plasmablasts. However, it is unclear whether B cell populations in individuals with mild COVID-19 are similarly skewed. In this study, we use single-cell RNA sequencing of B cells to show that in contrast to patients with severe COVID-19, subjects with mildly symptomatic COVID-19 have B cell repertoires enriched for clonally diverse, somatically hypermutated memory B cells ∼30 d after the onset of symptoms. This provides evidence that B cell responses are less disrupted in mild COVID-19 and result in the production of memory B cells.

The skin lesion erythema migrans (EM) is an initial sign of the Ixodes tick-transmitted Borreliella spirochetal infection known as Lyme disease. T cells and innate immune cells have previously been shown to predominate the EM lesion and promote the reaction. Despite the established importance of B cells and antibodies in preventing infection, the role of B cells in the skin immune response to Borreliella is unknown. Here, we used single-cell RNA-Seq in conjunction with B cell receptor (BCR) sequencing to immunophenotype EM lesions and their associated B cells and BCR repertoires. We found that B cells were more abundant in EM in comparison with autologous uninvolved skin; many were clonally expanded and had circulating relatives. EM-associated B cells upregulated the expression of MHC class II genes and exhibited preferential IgM isotype usage. A subset also exhibited low levels of somatic hypermutation despite a gene expression profile consistent with memory B cells. Our study demonstrates that single-cell gene expression with paired BCR sequencing can be used to interrogate the sparse B cell populations in human skin and reveals that B cells in the skin infection site in early Lyme disease expressed a phenotype consistent with local antigen presentation and antibody production.

While inhibition of T cell co-inhibitory receptors has revolutionized cancer therapy, the mechanisms governing their expression on human T cells have not been elucidated. Type 1 interferon (IFN-I) modulates T cell immunity in viral infection, autoimmunity, and cancer, and may facilitate induction of T cell exhaustion in chronic viral infection1,2. Here we show that IFN-I regulates co-inhibitory receptors expression on human T cells, inducing PD-1/TIM-3/LAG-3 while surprisingly inhibiting TIGIT expression. High-temporal-resolution mRNA profiling of IFN-I responses enabled the construction of dynamic transcriptional regulatory networks uncovering three temporal transcriptional waves. Perturbation of key transcription factors on human primary T cells revealed both canonical and non-canonical IFN-I transcriptional regulators, and identified unique regulators that control expression of co-inhibitory receptors. To provide direct in vivo evidence for the role of IFN-I on co-inhibitory receptors, we then performed single cell RNA-sequencing in subjects infected with SARS-CoV-2, where viral load was strongly associated with T cell IFN-I signatures. We found that the dynamic IFN-I response in vitro closely mirrored T cell features with acute IFN-I linked viral infection, with high LAG3 and decreased TIGIT expression. Finally, our gene regulatory network identified SP140 as a key regulator for differential LAG3 and TIGIT expression. The construction of co-inhibitory regulatory networks induced by IFN-I with identification of unique transcription factors controlling their expression may provide targets for enhancement of immunotherapy in cancer, infectious diseases, and autoimmunity.

SUMMARYMultisystem inflammatory syndrome in children (MIS-C) is a life-threatening post-infectious complication occurring unpredictably weeks after mild or asymptomatic SARS-CoV2 infection in otherwise healthy children. Here, we define immune abnormalities in MIS-C compared to adult COVID-19 and pediatric/adult healthy controls using single-cell RNA sequencing, antigen receptor repertoire analysis, unbiased serum proteomics, andin vitroassays. Despite no evidence of active infection, we uncover elevated S100A-family alarmins in myeloid cells and marked enrichment of serum proteins that map to myeloid cells and pathways including cytokines, complement/coagulation, and fluid shear stress in MIS-C patients. Moreover, NK and CD8 T cell cytotoxicity genes are elevated, and plasmablasts harboring IgG1 and IgG3 are expanded. Consistently, we detect elevated binding of serum IgG from severe MIS-C patients to activated human cardiac microvascular endothelial cells in culture. Thus, we define immunopathology features of MIS-C with implications for predicting and managing this SARS-CoV2-induced critical illness in children.

T cells provide critical immune surveillance to the central nervous system (CNS), and the cerebrospinal fluid (CSF) is thought to be a main route for their entry. Further characterization of the state of T cells in the CSF in healthy individuals is important for understanding how T cells provide protective immune surveillance without damaging the delicate environment of the CNS and providing tissue-specific context for understanding immune dysfunction in neuroinflammatory disease. Here, we have profiled T cells in the CSF of healthy human donors and have identified signatures related to cytotoxic capacity and tissue adaptation that are further exemplified in clonally expanded CSF T cells. By comparing profiles of clonally expanded T cells obtained from the CSF of patients with multiple sclerosis (MS) and healthy donors, we report that clonally expanded T cells from the CSF of patients with MS have heightened expression of genes related to T cell activation and cytotoxicity.

A dysregulated immune response against the SARS-CoV-2 virus plays a critical role in severe COVID-19. However, the molecular and cellular mechanisms by which the virus causes lethal immunopathology are poorly understood. Here, we utilize multiomics single-cell analysis to probe dynamic immune responses in patients with stable or progressive manifestations of COVID-19, and assess the effects of tocilizumab, an anti-IL-6 receptor monoclonal antibody. Coordinated profiling of gene expression and cell lineage protein markers reveals a prominent type-1 interferon response across all immune cells, especially in progressive patients. An anti-inflammatory innate immune response and a pre-exhaustion phenotype in activated T cells are hallmarks of progressive disease. Skewed T cell receptor repertoires in CD8+ T cells and uniquely enriched V(D)J sequences are also identified in COVID-19 patients. B cell repertoire and somatic hypermutation analysis are consistent with a primary immune response, with possible contribution from memory B cells. Our in-depth immune profiling reveals dyssynchrony of the innate and adaptive immune interaction in progressive COVID-19, which may contribute to delayed virus clearance and has implications for therapeutic intervention.

Combining transcriptomic and TCRαβ repertoire analysis of circulating and tumor-infiltrating CD8 T cells from patients with metastatic melanoma, Lucca et al. identify a blood-based population with effector properties that reflect those of clonally related tumor-resident T cells., Understanding the relationship between tumor and peripheral immune environments could allow longitudinal immune monitoring in cancer. Here, we examined whether T cells that share the same TCRαβ and are found in both tumor and blood can be interrogated to gain insight into the ongoing tumor T cell response. Paired transcriptome and TCRαβ repertoire of circulating and tumor-infiltrating T cells were analyzed at the single-cell level from matched tumor and blood from patients with metastatic melanoma. We found that in circulating T cells matching clonally expanded tumor-infiltrating T cells (circulating TILs), gene signatures of effector functions, but not terminal exhaustion, reflect those observed in the tumor. In contrast, features of exhaustion are displayed predominantly by tumor-exclusive T cells. Finally, genes associated with a high degree of blood–tumor TCR sharing were overexpressed in tumor tissue after immunotherapy. These data demonstrate that circulating TILs have unique transcriptional patterns that may have utility for the interrogation of T cell function in cancer immunotherapy.

Foxp3+ regulatory T cells (Treg cells) are the central component of peripheral immune tolerance. Whereas a dysregulated Treg cytokine signature has been observed in autoimmune diseases, the regulatory mechanisms underlying pro- and anti-inflammatory cytokine production are elusive. Here, we identify an imbalance between the cytokines IFN-γ and IL-10 as a shared Treg signature present in patients with multiple sclerosis and under high-salt conditions. RNA-sequencing analysis on human Treg subpopulations revealed β-catenin as a key regulator of IFN-γ and IL-10 expression. The activated β-catenin signature was enriched in human IFN-γ+ Treg cells, as confirmed in vivo with Treg-specific β-catenin-stabilized mice exhibiting lethal autoimmunity with a dysfunctional Treg phenotype. Moreover, we identified prostaglandin E receptor 2 (PTGER2) as a regulator of IFN-γ and IL-10 production under a high-salt environment, with skewed activation of the β-catenin-SGK1-Foxo axis. Our findings reveal a novel PTGER2-β-catenin loop in Treg cells linking environmental high-salt conditions to autoimmunity.

In recent years, the understanding of regulatory T cell (Treg cell) biology has expanded considerably. Key observations have challenged the traditional definition of Treg cells and have provided insight into the underlying mechanisms responsible for the development of autoimmune diseases, with new therapeutic strategies that improve disease outcome. This Review summarizes the newer concepts of Treg cell instability, Treg cell plasticity and tissue-specific Treg cells, and their relationship to autoimmunity. Those three main concepts have changed the understanding of Treg cell biology: how they interact with other immune and non-immune cells; their functions in specific tissues; and the implications of this for the pathogenesis of autoimmune diseases.

The introduction of immunotherapy with checkpoint receptor blockade has changed the treatment of advanced cancers, at times inducing prolonged remission. Nevertheless, the success rate of the approach is variable across patients and different tumor types, and treatment is often accompanied by severe immune-related side effects, suggesting the importance of co-inhibitory pathway for both prevention of autoimmunity and failure of tumor rejection. A better understanding of how to uncouple anti-tumor activity from loss of self-tolerance is necessary in order to increase the therapeutic efficacy of checkpoint immunotherapy. In this review, we describe basic concepts of T cell exhaustion that occur in cancer, highlighting the role of co-inhibitory receptors in contributing to this process while preventing immunopathology. By providing an overview of the current therapeutic success and immune-related burden of secondary effects of checkpoint immunotherapy, we illustrate the “double-edged sword” related to interference with immune-regulatory pathways. Finally, since achieving tumor rejection while preserving self-tolerance is particularly important for the central nervous system, we analyze the case for checkpoint immunotherapy in glioblastoma, the most common adult brain tumor.

Foxp3(+) regulatory T cells (Tregs) exhibit plasticity, which dictates their function. Secretion of the inflammatory cytokine IFNγ, together with the acquisition of a T helper 1 (Th1)-like effector phenotype as observed in cancer, infection, and autoimmune diseases, is associated with loss of Treg suppressor function through an unknown mechanism. Here, we describe the signaling events driving the generation of human Th1-Tregs. Using a genome-wide gene expression approach and pathway analysis, we identify the PI3K/AKT/Foxo1/3 signaling cascade as the major pathway involved in IFNγ secretion by human Tregs. Furthermore, we describe the opposing roles of AKT isoforms in Th1-Treg generation ex vivo Finally, we employ multiple sclerosis as an in vivo model with increased but functionally defective Th1-Tregs. We show that the PI3K/AKT/Foxo1/3 pathway is activated in ex vivo-isolated Tregs from untreated relapsing-remitting MS patients and that blockade of the pathway inhibits IFNγ secretion and restores the immune suppressive function of Tregs. These data define a fundamental pathway regulating the function of human Tregs and suggest a novel treatment paradigm for autoimmune diseases.

Th1 Tregs are characterized by the acquisition of proinflammatory cytokine secretion and reduced suppressor activity. Th1 Tregs are found at increased frequency in autoimmune diseases, including type 1 diabetes and multiple sclerosis (MS). We have previously reported that in vitro stimulation with IL-12 recapitulates the functional and molecular features of MS-associated Th1 Tregs, revealing a central role for hyperactivation of the Akt pathway in their induction. TIGIT is a newly identified coinhibitory receptor that marks Tregs that specifically control Th1 and Th17 responses. Here, we report that signaling through TIGIT counteracts the action of IL-12 in inducing the Th1 program. Specifically, TIGIT signaling represses production of IFN-γ and T-bet expression and restores suppressor function in Tregs treated with IL-12. FoxO1 functional inhibition abolishes the protective effect of TIGIT, indicating that TIGIT signaling promotes FoxO1 nuclear localization. Consistent with this observation, signaling through TIGIT leads to a rapid suppression of Akt function and FoxO1 phosphorylation. Finally, TIGIT stimulation reduces the production of IFN-γ and corrects the suppressor defect of Tregs from patients with MS. Our results indicate an important role for TIGIT in controlling the functional stability of Tregs through repression of Akt, suggesting that the TIGIT pathway could be targeted for immunomodulatory therapies in human autoimmune disorders.

Humans have had a long and complex relationship with salt. Although highly valued in many societies, dietary salt has long been associated with high blood pressure1–3 and, more recently, with other diseases.4–6 Some individuals with hypertension often display salt-sensitive blood pressure changes, which is a condition more prevalent among blacks, older people, and individuals with renal insufficiency or diabetes mellitus.7–9 In general, for those with salt-sensitive hypertension, excess sodium intake is associated with higher blood pressure, whereas a low-salt diet decreases blood pressure.3 In spite of this well-known association, the basic molecular and cellular mechanisms underlying the effects of salt on blood pressure regulation are still not well understood. Furthermore, individuals with high blood pressure are at increased risk for multiple diseases (ie, coronary artery disease, heart failure, stroke, and renal disease) although at present whether or not a high dietary salt intake can directly lead to these diseases (ie, in the absence of hypertension) is not known. Our understanding of the effect of salt on health has grown even more complex recently. Researchers have reported a new connection between salt and autoimmunity: a high-salt diet was shown to accelerate autoimmune activity in a mouse model of multiple sclerosis.10,11 In addition, a close connection between hypertension and the immune system has been revealed.12–16 However, the causal relationships between salt, immunity, and hypertension (eg, how salt could mediate interactions between the immune system and the vasculature, brain, or kidney to increase blood pressure) are not well understood. The National Heart, Lung, and Blood Institute convened a Working Group (WG) in 2014 to discuss this new emerging scientific area in hypertension research. The WG brought together experts from diverse backgrounds including hypertension, epidemiology, preeclampsia, cardiovascular disease, …

A subset of human regulatory T cells (Tregs) can secrete IFN-γ or IL-17 and thus share features of TH1 or TH17 effector cells, and lose suppressive function. The main factors driving this differentiation of Tregs towards a pro-inflammatory phenotype include IL-12 for TH1-like and IL-6 for TH17-type Tregs. In this study we show that Tregs of patients with de novo autoimmune hepatitis (dAIH) display increased frequencies of pro-inflammatory IFN-γ and IL-17 cytokines. Irrespective of a fully demethylated FOXP3 locus, Tregs of subjects with de novo autoimmune hepatitis are functionally impaired. In line with the observed Treg phenotype, we detected the presence of two dominant cytokines (IL-12 and IL-6) clustering with CD68+ monocyte/macrophage cells in livers of subjects with de novo autoimmune hepatitis and isolated monocytes of subjects with de novo autoimmune hepatitis secrete high levels of pro-inflammatory IL-12 and IL-6 suggesting that this inflammatory milieu is key for functional impairment of Tregs. Importantly, the blockade of IFN-γ partially restores suppressive function of Tregs of subjects with de novo autoimmune hepatitis indicating that monocyte/macrophage derived triggers might play a central role in Treg dysfunction and pathogenesis of de novo autoimmune hepatitis.

The cell surface glycoprotein CD6 is expressed on leukocytes and mediates T cell trafficking across endothelial cell barriers. There is evidence suggesting that CD6 is implicated in the pathogenesis of autoimmune diseases, including multiple sclerosis (MS) and rheumatoid arthritis (RA). CD166, the physiological ligand of CD6, is expressed on endothelial cells in the central nervous system and in the collagen tissue of joints as well as on the cell surface of synovial fibroblasts. Animal models and in vitro experiments have shown that CD166 facilitates leukocyte trafficking into the central nervous system and mediates interactions of synovial cells with T lymphocytes, thereby representing a possible common mechanism of pathogenesis in MS and RA. In recent years, genome-wide association studies (GWAS) have established a genetic link between CD6 and MS. The single nucleotide polymorphism (SNP) rs17824933 in the CD6 gene has been identified and validated as a genetic risk factor for the development of MS. The SNP is associated with altered CD4+ T cell functions and with the expression of alternative CD6 splice variants in T cells. Several other independent CD6 gene polymorphisms have been associated with disease susceptibility or with clinical features such as worse attack recovery in MS. In addition to the genetic associations found in MS, an allelic variant of the CD6 gene correlates with clinical response to tumor necrosis factor-α (TNF-α) inhibitors in patients with RA. Preliminary data indicate that anti-CD6 blockade may be a promising tool for the treatment of RA and psoriasis. Taken together, genetic associations and clinical observations provide new evidence for a role of CD6 in autoimmunity.

Ipilimumab is a monoclonal antibody that prolongs survival in patients with metastatic melanoma.1 It targets the coinhibitory receptor cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4). CTLA-4 signaling induces a state of T-cell unresponsiveness, which facilitates tumor escape from immune surveillance. Blockade of CTLA-4 is believed to shift the immune status from T-cell exhaustion to a functional antitumor response. Anti-CTLA-4 therapy is associated with immune-related adverse events in 64% of patients. Autoimmunity involving the nervous system has a low incidence and manifests predominantly as peripheral inflammatory neuropathy.2 We report new-onset inflammatory CNS demyelination in an ipilimumab-treated melanoma patient (figure), confirmed by histology and associated with enhanced responses of myelin-reactive CD4+ T cells.

Immunotherapy has emerged as a potent approach for treating aggressive cancers, such as non–small-cell lung tumors and metastatic melanoma. Clinical trials are now in progress for patients with malignant gliomas; however, a better understanding of how these tumors escape immune surveillance is required to enhance antitumor immune responses. With gliomas, the recruitment of CD8+ T cells to the tumor is impaired, in part preventing containment or elimination of the tumor. In this issue of the JCI, Kohanbash and colleagues present an elegant dissection of how gliomas exploit an enzymatic activity acquired through a common mutation to abrogate the migration of CD8+ T cells to the tumor. They show that the oncometabolite 2-hydroxyglutarate (2HG), generated by mutated forms of isocitrate dehydrogenase (IDH1 and IDH2), reduces the expression of STAT1, thereby limiting the production of the chemokines CXCL9 and CXCL10. As a result, IDH1-mutated tumors are less effectively infiltrated by CD8+ T cells, contributing to tumor escape. Finally, in mice harboring syngeneic gliomas, an inhibitor of 2HG synthesis complemented vaccination to ameliorate tumor control. Understanding how to increase immune infiltration of gliomas represents a key first step in achieving tumor destruction through immunotherapy.

Multiple sclerosis (MS) is a genetically mediated autoimmune disease characterized by inflammation in the central nervous system (CNS). Disease onset is thought to occur when autoreactive T cells orchestrate a cascade of events in the CNS resulting in white and grey matter inflammation and axonal degeneration. It is unclear what triggers the activation of CNS-reactive T cells and their polarization into inflammatory subsets. Mounting evidence from animal and human studies supports the hypothesis that the gut microbiome affects MS pathogenesis. We investigated the association between the gut microbiome and inflammatory T cell subsets in relapsing-remitting MS patients and healthy controls. Gut microbiome composition was characterized by sequencing the V4 region of the 16S rRNA gene from fecal DNA, and inflammatory T cell subsets were characterized by flow cytometry. We identified an altered gut microbiome in MS patients, including decreased abundance of Coprococcus, Clostridium, and an unidentified Ruminococcaceae genus. Among circulating immune cells, patients had increased expression of CXCR3 in both CD4 and CD8 T cells, and both CD4+CXCR3+ and CD8+CXCR3+ populations expressing the gut-homing α4β7 integrin receptor were increased. Finally, we show that alpha diversity inversely correlated with a CXCR3+ Th1 phenotype in MS. These findings indicate the presence of an aberrant gut-immune axis in patients with MS., Highlights • Patients with MS exhibited decreased alpha diversity in the composition of their gut bacteria compared to healthy controls. • Circulating lymphocytes from MS patients were enriched for Th1 and Th1-17 memory CD4+ cells and for CXCR5+ memory CD4+ cells. • A larger proportion of Th1 and Th1–Th17 ​cells expressed the gut homing receptor α4β7 compared to Th17 ​cells. • The frequency of Th1, Th1-17 and CD8 T cells co-expressing α4β7 and CXCR3 wereincreased in patients compared to controls. • Reduced alpha diversity correlated significantly with expression of CXCR3+ on CD8+ T-cells and CXCR5— memory T-cells.

Epigenetic annotation studies of genetic risk variants for multiple sclerosis (MS) implicate dysfunctional lymphocytes in MS susceptibility; however, the role of central nervous system (CNS) cells remains unclear. We investigated the effect of the risk variant, rs7665090G, located near NFKB1, on astrocytes. We demonstrated that chromatin is accessible at the risk locus, a prerequisite for its impact on astroglial function. The risk variant was associated with increased NF-κB signaling and target gene expression, driving lymphocyte recruitment, in cultured human astrocytes and astrocytes within MS lesions, and with increased lesional lymphocytic infiltrates and lesion sizes. Thus, our study establishes a link between genetic risk for MS (rs7665090G) and dysfunctional astrocyte responses associated with increased CNS access for peripheral immune cells. MS may therefore result from variant-driven dysregulation of the peripheral immune system and of the CNS, where perturbed CNS cell function aids in establishing local autoimmune inflammation., It is unclear if multiple sclerosis (MS) genetic susceptibility can be mediated through perturbations of CNS-intrinsic pathways. Authors show that the rs7665090 risk variant is associated with astrocyte responses that enhance lymphocyte recruitment, and with increased lymphocyte infiltration and lesion sizes in MS lesions.

A recent epidemic of Zika virus in the Americas, affecting well over a million people, caused substantial mortality and morbidity, including Guillain–Barre syndrome, microcephaly and other fetal developmental defects1,2. Preventive and therapeutic measures that specifically target the virus are not readily available. The transmission of Zika virus is predominantly mosquito-borne, and Aedes aegypti mosquitoes serve as a key vector for Zika virus3. Here, to identify salivary factors that modulate mosquito-borne Zika virus infection, we focused on antigenic proteins in mice that were repeatedly bitten by mosquitoes and developed antibodies against salivary proteins. Using a yeast surface display screen, we identified five antigenic A. aegypti salivary proteins in mice. Antiserum against one of these five proteins—A. aegypti bacteria-responsive protein 1 (AgBR1)—suppressed early inflammatory responses in the skin of mice bitten by Zika-virus-infected mosquitoes. AgBR1 antiserum also partially protected mice from lethal mosquito-borne—but not needle-injected—Zika virus infection. These data suggest that AgBR1 is a target for the prevention of mosquito-transmitted Zika virus infection. A yeast surface display screen identifies five Aedes aegypti salivary proteins that are antigenic in mice repeatedly bitten by these mosquitoes. Antiserum against one of these proteins, Anopheles gambiae bacteria-responsive 1, partially protected mice against lethal mosquito-borne Zika virus infection.

Fingolimod is an approved therapeutic option for patients with relapsing-remitting multiple sclerosis that primarily functions by sequestering T cells in lymph nodes inhibiting their egress to the central nervous system. However, recent data suggests that Fingolimod may also directly affect the immune cell function. Here we examined the in vivo effects of Fingolimod in modulating the phenotype and function of T cell and Foxp3 regulatory T cell populations in patients with multiple sclerosis under Fingolimod treatment. Besides decreasing the cell numbers in peripheral blood and sera levels of pro-inflammatory cytokines, Fingolimod inhibited the expression of Th1 and Th17 cytokines on CD4(+) T cells and increased the expression of exhaustion markers. Furthermore, treatment increased the frequency of regulatory T cells in blood and inhibited the Th1-like phenotype that is characteristic of patients with multiple sclerosis, augmenting the expression of markers associated with increased suppressive function. Overall, our data suggest that Fingolimod performs other important immunomodulatory functions besides altering T cell migratory capacities, with consequences for other autoimmune pathologies characterized by excessive Th1/Th17 responses and Th1-like regulatory T cell effector phenotypes.

Central nervous system (CNS) immune activation in an important driver of neuronal injury during several neurodegenerative and neuroinflammatory diseases. During HIV infection, CNS immune activation is associated with high rates of neurocognitive impairment, even with sustained long-term suppressive antiretroviral therapy (ART). However, the cellular subsets that drive immune activation and neuronal damage in the CNS during HIV infection and neurological conditions remain unknown, in part because CNS cells are difficult to access in living humans. Using single cell RNA sequencing (scRNA-seq) on cerebrospinal fluid (CSF) and blood from adults with HIV, we identified a rare (

Cellular therapies with CD4+ T regulatory cells (Tregs) hold promise of efficacious treatment for the variety of autoimmune and allergic diseases as well as posttransplant complications. Nevertheless, current manufacturing of Tregs as a cellular medicinal product varies between different laboratories, which in turn hampers precise comparisons of the results between the studies performed. While the number of clinical trials testing Tregs is already substantial, it seems to be crucial to provide some standardized characteristics of Treg products in order to minimize the problem. We have previously developed reporting guidelines called minimum information about tolerogenic antigen-presenting cells, which allows the comparison between different preparations of tolerance-inducing antigen-presenting cells. Having this experience, here we describe another minimum information about Tregs (MITREG). It is important to note that MITREG does not dictate how investigators should generate or characterize Tregs, but it does require investigators to report their Treg data in a consistent and transparent manner. We hope this will, therefore, be a useful tool facilitating standardized reporting on the manufacturing of Tregs, either for research purposes or for clinical application. This way MITREG might also be an important step toward more standardized and reproducible testing of the Tregs preparations in clinical applications. This work was supported by a grant from the European Cooperation in Science and Technology (COST) for the AFACTT project (Action to Focus and Accelerate Cell-based Tolerance-inducing Therapies; BM1305). COST is part of the EU Framework Programme Horizon 2020. peer-reviewed

Multiple sclerosis (MS) is a genetically mediated autoimmune disease of the central nervous system. Allelic variants lead to lower thresholds of T-cell activation resulting in activation of autoreactive T cells. Environmental factors, including, among others, diet, vitamin D, and smoking, in combination with genetic predispositions, play a substantial role in disease development and activation of autoreactive T cells. FoxP3(+) regulatory T cells (Tregs) have emerged as central in the control of autoreactive T cells. A consistent finding in patients with MS is defects in Treg cell function with reduced suppression of effector T cells and production of proinflammatory cytokines. Emerging data suggests that functional Tregs become effector-like T cells with loss of function associated with T-bet expression and interferon γ (IFN-γ) secretion.

Substantial effort has been made over the last six decades to identify biomarkers for multiple sclerosis that can improve disease diagnosis, predict disease progression, and improve clinical outcomes. However, to date, few of these findings have proven clinically useful. In this review, we address the current state of MS biomarker research. We start by discussing biomarkers currently in clinical use including Oligoclonal bands, MRI, and JC viral titers. We go on to discuss other potential biomarkers from MS serum and cerebrospinal fluid including Markers of neurodegeneration including neurofilament and GFAP, the monocyte macrophage marker CD163, the glial activation marker YKL-40, the B cell chemoattractant CXCL13, miRNA and mRNA, myelin reactive t cells, Kir4.1 antibodies, osteopontin, and microbiome associated lipopeptides. Finally, we discuss the current state of MS genetic studies and how genetics may offer simple, reliable testing for MS susceptibility and progression.

FOXP3+ Tregs are central for the maintenance of self-tolerance and can be defective in autoimmunity. In multiple sclerosis and type-1 diabetes, dysfunctional self-tolerance is partially mediated by a population of IFNγ-secreting Tregs. It was previously reported that increased NaCl concentrations promote the induction of proinflammatory Th17 cells and that high-salt diets exacerbate experimental models of autoimmunity. Here, we have shown that increasing NaCl, either in vitro or in murine models via diet, markedly impairs Treg function. NaCl increased IFNγ secretion in Tregs, and reducing IFNγ — either by neutralization with anti-IFNγ antibodies or shRNA-mediated knockdown — restored suppressive activity in Tregs. The heightened IFNγ secretion and loss of Treg function were mediated by the serum/glucocorticoid-regulated kinase (SGK1). A high-salt diet also impaired human Treg function and was associated with the induction of IFNγ-secreting Tregs in a xenogeneic graft-versus-host disease model and in adoptive transfer models of experimental colitis. Our results demonstrate a putative role for an environmental factor that promotes autoimmunity by inducing proinflammatory responses in CD4 effector cells and Treg pathways.

Glioblastoma is the most common primary brain tumour in adults. Prognosis is poor: even with the current gold-standard first-line treatment—maximal safe resection and combination of radiotherapy with temozolomide chemotherapy—the median overall survival time is only approximately 15–17 months, because the tumour recurs in virtually all patients, and no commonly accepted standard treatment for recurrent disease exists. Several targeted agents have failed to improve patient outcomes in glioblastoma. Immunotherapy with immune checkpoint inhibitors such as ipilimumab, nivolumab, and pembrolizumab has provided relevant clinical improvements in other advanced tumours for which conventional therapies have had limited success, making immunotherapy an appealing strategy in glioblastoma. This Review summarizes current knowledge on immune checkpoint modulators and evaluates their potential role in glioblastoma on the basis of preclinical studies and emerging clinical data. Furthermore, we discuss challenges that need to be considered in the clinical development of drugs that target immune checkpoint pathways in glioblastoma, such as specific properties of the immune system in the CNS, issues with radiological response assessment, and potential interactions with established and emerging treatment strategies.

Epigenetic annotation studies of genetic risk variants for multiple sclerosis (MS) implicate dysfunctional lymphocytes in MS susceptibility; however, the role of central nervous system (CNS) cells remains unclear. We investigated the effect of the risk variant, rs7665090G, located near NFKB1, on astrocytes. We demonstrated that chromatin is accessible at the risk locus, a prerequisite for its impact on astroglial function. The risk variant was associated with increased NF-κB signaling and target gene expression driving lymphocyte recruitment in cultured human astrocytes and astrocytes within MS lesions, and with increased lesional lymphocytic infiltrates. In MS patients, the risk genotype was associated with increased lesion volumes on MRI. Thus, we established that the rs7665090G variant perturbs astrocyte function resulting in increased CNS access for peripheral immune cells. MS may thus result from variant-driven dysregulation of the peripheral immune system and the CNS, where perturbed CNS cell function aids in establishing local autoimmune inflammation.One Sentence SummaryThe NF-κB relevant multiple sclerosis risk variant, rs7665090G, drives astrocyte responses that promote lesion formation.

Annual influenza vaccinations are currently recommended for all individuals 6 months and older. Antibodies induced by vaccination are an important mechanism of protection against infection. Despite the overall public health success of influenza vaccination, many individuals fail to induce a substantial antibody response. Systems-level immune profiling studies have discerned associations between transcriptional and cell subset signatures with the success of antibody responses. However, existing signatures have relied on small cohorts and have not been validated in large independent studies. We leveraged multiple influenza vaccination cohorts spanning distinct geographical locations and seasons from the Human Immunology Project Consortium (HIPC) and the Center for Human Immunology (CHI) to identify baseline (i.e., before vaccination) predictive transcriptional signatures of influenza vaccination responses. Our multicohort analysis of HIPC data identified nine genes (RAB24, GRB2, DPP3, ACTB, MVP, DPP7, ARPC4, PLEKHB2, and ARRB1) and three gene modules that were significantly associated with the magnitude of the antibody response, and these associations were validated in the independent CHI cohort. These signatures were specific to young individuals, suggesting that distinct mechanisms underlie the lower vaccine response in older individuals. We found an inverse correlation between the effect size of signatures in young and older individuals. Although the presence of an inflammatory gene signature, for example, was associated with better antibody responses in young individuals, it was associated with worse responses in older individuals. These results point to the prospect of predicting antibody responses before vaccination and provide insights into the biological mechanisms underlying successful vaccination responses.

Emergent responses of the immune system result from the integration of molecular and cellular networks over time and across multiple organs. High-content and high-throughput analysis technologies, concomitantly with data-driven and mechanistic modeling, hold promise for the systematic interrogation of these complex pathways. However, connecting genetic variation and molecular mechanisms to individual phenotypes and health outcomes has proven elusive. Gaps remain in data, and disagreements persist about the value of mechanistic modeling for immunology. Here, we present the perspectives that emerged from the National Institute of Allergy and Infectious Disease (NIAID) workshop 'Complex Systems Science, Modeling and Immunity' and subsequent discussions regarding the potential synergy of high-throughput data acquisition, data-driven modeling, and mechanistic modeling to define new mechanisms of immunological disease and to accelerate the translation of these insights into therapies.

mmune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) have been highly successful in the treatment of cancer. While PD-1 expression has been widely investigated, its role in CD4⁺ effector T cells in the setting of health and cancer remains unclear, particularly in the setting of glioblastoma multiforme (GBM), the most aggressive and common form of brain cancer. We examined the functional and molecular features of PD-1⁺ CD4⁺ CD25—CD127⁺ Foxp3—effector cells in healthy subjects and in patients with GBM. In healthy subjects, we found that PD-1⁺ CD4⁺ effector cells are dysfunctional: they do not proliferate but can secrete large quantities of IFNγ. Strikingly, blocking antibodies against PD-1 did not rescue proliferation. RNA-sequencing revealed features of exhaustion in PD-1⁺ CD4 effectors. In the context of GBM, tumors were enriched in PD-1⁺ CD4⁺ effectors that were similarly dysfunctional and unable to proliferate. Furthermore, we found enrichment of PD-1⁺ TIM-3⁺ CD4⁺ effectors in tumors, suggesting that co-blockade of PD-1 and TIM-3 in GBM may be therapeutically beneficial. RNA-sequencing of blood and tumors from GBM patients revealed distinct differences between CD4⁺ effectors from both compartments with enrichment in multiple gene sets from tumor infiltrating PD-1[superscript —]CD4⁺ effectors cells. Enrichment of these gene sets in tumor suggests a more metabolically active cell state with signaling through other co-receptors. PD-1 expression on CD4 cells identifies a dysfunctional subset refractory to rescue with PD-1 blocking antibodies, suggesting that the influence of immune checkpoint inhibitors may involve recovery of function in the PD-1[superscript —]CD4⁺ T cell compartment. Additionally, co-blockade of PD-1 and TIM-3 in GBM may be therapeutically beneficial., Daniel Lowther

We assembled and analyzed genetic data of 47,351 multiple sclerosis (MS) subjects and 68,284 control subjects and establish a reference map of the genetic architecture of MS that includes 200 autosomal susceptibility variants outside the major histocompatibility complex (MHC), one chromosome X variant, and 32 independent associations within the extended MHC. We used an ensemble of methods to prioritize up to 551 potentially associated MS susceptibility genes, that implicate multiple innate and adaptive pathways distributed across the cellular components of the immune system. Using expression profiles from purified human microglia, we do find enrichment for MS genes in these brain - resident immune cells. Thus, while MS is most likely initially triggered by perturbation of peripheral immune responses the functional responses of microglia and other brain cells are also altered and may have a role in targeting an autoimmune process to the central nervous system.One Sentence Summary:We report a detailed genetic and genomic map of multiple sclerosis, and describe the role of putatively affected genes in the peripheral immune system and brain resident microglia.

Influenza remains a significant cause of morbidity and mortality in older adults, with 90% of annual influenza-related deaths occurring in individuals older than 65 years [1]. Although the seasonal inactivated vaccine is recommended for prevention, a meta-analysis of 64 studies of influenza vaccine response in older adults (>65 years) revealed an efficacy of 23% for the prevention of influenzalike illness [2]. This poor vaccine response is a result in part of age-associated alterations in immune function [3]. Immunosenescence affects the adaptive immune system, resulting in impairments in B- and T-cell development, signaling, and antigen receptor repertoire [4–8]. The human innate immune system is also affected by aging, with chronic inflammation arising from sources including age-associated herpesvirus reactivation and increased non–cell-associated DNA reflected in elevated levels of cytokines and acute phase reactants; such inflammation contributes to dysregulated innate immune function, particularly of pattern recognition receptors such as Toll-like receptors (TLRs) [9]. However, how aging affects human innate immunity to influenza vaccination remains incompletely understood. Here, we evaluated monocyte function at baseline and after immunization with the inactivated influenza vaccine in a cohort of young and older adults.

West Nile virus (WNV) infection is usually asymptomatic but can cause severe neurological disease and death, particularly in older patients, and how individual variations in immunity contribute to disease severity is not yet defined. Animal studies identified a role for several immunity-related genes that determine the severity of infection. We have integrated systems-level transcriptional and functional data sets from stratified cohorts of subjects with a history of WNV infection to define whether these markers can distinguish susceptibility in a human population. Transcriptional profiles combined with immunophenotyping of primary cells identified a predictive signature of susceptibility that was detectable years after acute infection (67% accuracy), with the most prominent alteration being decreased IL1B induction followingex vivoinfection of macrophages with WNV. Deconvolution analysis also determined a significant role for CXCL10 expression in myeloid dendritic cells. This systems analysis identified markers of pathogenic mechanisms and offers insights into potential therapeutic strategies.

T-cell immunoglobulin and mucin domain 3 (TIM-3) is an Ig-superfamily member expressed on IFN-γ-secreting Th1 and Tc1 cells and was identified as a negative regulator of immune tolerance. TIM-3 is expressed by a subset of activated CD4+ T cells, and anti-CD3/anti-CD28 stimulation increases both the level of expression and the number of TIM-3+ T cells. In mice, TIM-3 is constitutively expressed on natural regulatory T (Treg) cells and has been identified as a regulatory molecule of alloimmunity through its ability to modulate CD4+ T-cell differentiation. Here, we examined TIM-3 expression on human Treg cells to determine its role in T-cell suppression. In contrast to mice, TIM-3 is not expressed on Treg cells ex vivo but is upregulated after activation. While TIM-3+ Treg cells with increased gene expression of LAG3, CTLA4, and FOXP3 are highly efficient suppressors of effector T (Teff) cells, TIM-3− Treg cells poorly suppressed Th17 cells as compared with their suppression of Th1 cells; this decreased suppression ability was associated with decreased STAT-3 expression and phosphorylation and reduced gene expression of IL10, EBI3, GZMB, PRF1, IL1Rα, and CCR6. Thus, our results suggest that TIM-3 expression on Treg cells identifies a population highly effective in inhibiting pathogenic Th1- and Th17-cell responses.

Prostaglandin E2 (PGE2) promotes Th17 expansion while otherwise inhibiting other CD4+ T cell subsets. Here, we identified a PGE2-dependent pathway that induces pathogenic Th17 cells in autoimmune disease and is regulated by the transcription factor RORC. Compared with other CD4+ cell types from healthy subjects, there is a surprising lack of the prostaglandin receptor EP2 on Th17 cells; therefore, we examined the hypothesis that RORγt, which is highly expressed in Th17 cells, mediates EP2 downregulation. Chromatin immunoprecipitation followed by DNA sequencing revealed that RORγt binds directly to Ptger2 (the gene encoding EP2 receptor) in Th17 cells isolated from WT mice. In Th17 cells isolated from humans, RORC repressed EP2 by directly silencing PTGER2 transcription, and knock down of RORC restored EP2 expression in Th17 cells. Compared with Th17 cells from healthy individuals, Th17 cells from patients with MS exhibited reduced RORC binding to the PTGER2 promoter region, resulting in higher EP2 levels and increased expression of IFN-γ and GM-CSF. Finally, overexpression of EP2 in Th17 cells from healthy individuals induced a specific program of inflammatory gene transcription that produced a pathogenic Th17 cell phenotype. These findings reveal that RORC directly regulates the effects of PGE2 on Th17 cells, and dysfunction of this pathway induces a pathogenic Th17 cell phenotype.

Regulatory T cells are the central element for the maintenance of peripheral tolerance. Several subtypes of regulatory T (Treg) cells have been described, and most of them belong to the CD4(+) T-helper (Th) cell lineage. These specific subtypes can be discriminated according to phenotype and function. Forkhead box protein 3 (FoxP3)-expressing natural Treg cells (Tregs) and IL-10-producing, T-regulatory type 1 cells (Tr1) are the best-studied types of CD4(+) regulatory T cells in humans and experimental animal models. It was shown that they play a crucial role during autoimmune neuroinflammation. Both cells types seem to be particularly important for multiple sclerosis (MS). Here, we discuss the role of CD4(+) regulatory T cells in autoimmune neuroinflammation with an emphasis on Tregs and Tr1 cells in MS.

Objective: We set out to characterize the clinical impact and functional consequences of rs1800693 G , the multiple sclerosis (MS) susceptibility allele found in the TNFRSF1A locus. Methods: We analyzed prospectively collected data on patients with MS to assess the role of the TNFRSF1A locus on disease course and treatment response. Using archival serum samples and freshly isolated monocytes from patients with MS and healthy subjects, we evaluated the effects of rs1800693 G and a second risk allele, R92Q, on immune function. Results: In 772 patients with MS, we see no evidence that rs1800693 G strongly influences clinical or radiographic indices of disease course and treatment response; thus, rs1800693 G appears to be primarily involved in the onset of MS. At the molecular level, this validated susceptibility allele generates an RNA isoform, TNFRSF1A Δ6, that lacks the transmembrane and cytoplasmic domains. While there was no measurable effect on serum levels of soluble TNFRSF1A, rs1800693 G appears to alter the state of monocytes, which demonstrate a more robust transcriptional response of CXCL10 and other genes in response to tumor necrosis factor (TNF)–α. We also report that activation of the TNF-α pathway results in altered expression of 6 other MS susceptibility genes, including T-cell activation rho GTPase activating protein ( TAGAP ) and regulator of G-protein signaling 1 ( RGS1 ), which are not previously known to be responsive to TNF-α. Conclusions: The MS rs1800693 G susceptibility allele affects the magnitude of monocyte responses to TNF-α stimulation, and the TNF pathway may be one network in which the effect of multiple MS genes becomes integrated.

CD226 costimulatory signals strongly promote Th1 differentiation, enhancing IFN-γ production by naive T cells. We recently reported that knockdown of CD226 on human T cells resulted in a decrease in T-bet and IFN-γ expression. However, the role of CD226 on Th2 and Th17 cells remains unknown. In this study, we found that CD226 and its ligand CD155 were decreased on Th2-polarized naive T cells, whereas both were highly expressed under Th17 conditions. Most IFN-γ– and IL-17–producing cells expressed high levels of CD226, but production of IL-13 did not correlate with CD226 expression. CD226 knockdown by lentiviral transduction resulted in increased STAT-6 phosphorylation, enhanced GATA3 expression, and consequently higher production of IL-4 and IL-13. Under Th17 conditions, CD226-depleted cells showed slightly impaired IL-17 secretion, suggesting that CD226 contributes, in part, to IL-17 production but is dispensable for Th17 cell generation. In line with these results, CD226 blockade with neutralizing Abs efficiently inhibited T cell activation and proliferation and production of IFN-γ and IL-17, whereas IL-13 secretion remained functional. Taken together, our results establish an important role for CD226 in differentially regulating the proinflammatory (Th1/Th17)/anti-inflammatory (Th2) balance, suggesting that the CD226/CD155 interaction could potentially be targeted in therapeutic approaches to human autoimmune diseases.