Autoantibodies to myelin oligodendrocyte glycoprotein (MOG) can induce demyelination and oligodendrocyte loss in models of multiple sclerosis (MS). Whether anti-MOG Abs play a similar role in patients with MS or inflammatory CNS diseases by epitope spreading is unclear. We have therefore examined whether autoantibodies that bind properly folded MOG protein are present in the CNS parenchyma of MS patients. IgG was purified from CNS tissue of 14 postmortem cases of MS and 8 control cases, including cases of encephalitis. Binding was assessed using two independent assays, a fluorescence-based solid-phase assay and a solution-phase RIA. MOG autoantibodies were identified in IgG purified from CNS tissue by solid-phase immunoassay in 7 of 14 cases with MS and 1 case of subacute sclerosing panencephalitis, but not in IgG from noninflamed control tissue. This finding was confirmed with a solution-phase RIA, which measures higher affinity autoantibodies. These data demonstrate that autoantibodies recognizing MOG are present in substantially higher concentrations in the CNS parenchyma compared with cerebrospinal fluid and serum in subjects with MS, indicating that local production/accumulation is an important aspect of autoantibody-mediated pathology in demyelinating CNS diseases. Moreover, chronic inflammatory CNS disease may induce autoantibodies by virtue of epitope spreading.
Summary: Driven by dramatic technological improvements, large-scale characterization of lymphocyte receptor repertoires via high-throughput sequencing is now feasible. Although promising, the high germline and somatic diversity, especially of B-cell immunoglobulin repertoires, presents challenges for analysis requiring the development of specialized computational pipelines. We developed the REpertoire Sequencing TOolkit (pRESTO) for processing reads from high-throughput lymphocyte receptor studies. pRESTO processes raw sequences to produce error-corrected, sorted and annotated sequence sets, along with a wealth of metrics at each step. The toolkit supports multiplexed primer pools, single- or paired-end reads and emerging technologies that use single-molecule identifiers. pRESTO has been tested on data generated from Roche and Illumina platforms. It has a built-in capacity to parallelize the work between available processors and is able to efficiently process millions of sequences generated by typical high-throughput projects.
Availability and implementation: pRESTO is freely available for academic use. The software package and detailed tutorials may be downloaded from http://clip.med.yale.edu/presto.
Supplementary data are available at Bioinformatics online.
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 following ex vivo infection 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.
Studying the activity of homogeneous regulatory T cell (Treg) populations will advance our understanding of their mechanisms of action and their role in human disease. Although isolating human Tregs exhibiting low expression of CD127 markedly increases purity, the resulting Treg populations are still heterogeneous. To examine the complexity of the Tregs defined by the CD127 phenotype in comparison with the previously described CD4+CD25hi subpopulations, we subdivided the CD25hi population of memory Tregs into subsets based on expression of CD127 and HLA-DR. These subsets exhibited differences in suppressive capacity, ability to secrete IL-10 and IL-17, Foxp3 gene methylation, cellular senescence, and frequency in neonatal and adult blood. The mature, short telomere, effector CD127loHLA-DR+ cells most strongly suppressed effector T cells within 48 h, whereas the less mature CD127lo HLA-DR− cells required 96 h to reach full suppressive capacity. In contrast, whereas the CD127+HLA-DR− cells also suppressed proliferation of effector cells, they could alternate between suppression or secretion of IL-17 depending upon the stimulation signals. When isolated from patients with multiple sclerosis, both the nonmature and the effector subsets of memory CD127lo Tregs exhibited kinetically distinct defects in suppression that were evident with CD2 costimulation. These data demonstrate that natural and not induced Tregs are less suppressive in patients with multiple sclerosis.
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 in particular 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.
qutoimmunity; regulatory T cells; Treg; Tr1; FoxP3; multiple sclerosis
Pattern recognition of microbes by Toll-like receptors (TLR) is critical for innate immune system activation. Although TLRs are expressed in human CD4+ T cells, their function is not well understood. Here we demonstrate that engaging TLR7 in CD4+ T cells induces intracellular calcium flux with activation of an NFATc2-dependent anergic gene expression program and T cell non-responsiveness. As chronic infections with RNA viruses such as HIV-1 induce profound CD4+ T cell dysfunction, we examined the role of TLR7-induced anergy in HIV-1 infection. TLR7 gene silencing markedly decreases the frequency of HIV-1-infected CD4+ T cells and restores cell responsiveness in those HIV-1+ CD4+ T cells. These results elucidate a previously unknown function for microbial pattern recognition receptors to down-regulate immune responses.
Background and objective
Acute disseminated encephalomyelitis (ADEM) and relapsing remitting multiple sclerosis share overlapping clinical, radiologic, and laboratory features at onset. Because autoantibodies may contribute to the pathogenesis of both diseases, we sought to identify autoantibody biomarkers capable of distinguishing them.
We used custom antigen arrays to profile anti-myelin-peptide autoantibodies in sera derived from individuals with pediatric ADEM (n = 15), pediatric multiple sclerosis (n = 11), and adult multiple sclerosis (n = 15). Using isotype-specific secondary antibodies,we profiled both IgG and IgM reactivities. We used Statistical Analysis of Microarrays to confirm differences in autoantibody reactivity profiles between ADEM and multiple sclerosis samples. We used Prediction Analysis of Microarrays to generate and validate prediction algorithms based on the autoantibody reactivity profiles.
ADEM was characterized by IgG autoantibodies targeting epitopes derived from myelin basic protein, proteolipid protein, myelin-associated oligodendrocyte basic glycoprotein, and alpha-B-crystallin. In contrast, multiple sclerosis was characterized by IgM autoantibodies targeting myelin basic protein, proteolipid protein, myelin-associated oligodendrocyte basic glycoprotein, and oligodendrocyte specific protein. We generated and validated prediction algorithms that distinguish ADEM serum (sensitivity 62–86%; specificity 56–79%) from multiple sclerosis serum (sensitivity 40–87%; specificity 62–86%) on the basis of combined IgG and IgM anti-myelin autoantibody reactivity to a small number of myelin peptides.
Combined profiles of serum IgG and IgM autoantibodies identify myelin antigens that may be useful for distinguishing multiple sclerosis from ADEM. Further studies are required to establish clinical utility. Further biological assays are required to delineate the pathogenic potential of these antibodies.
pediatric; multiple sclerosis; acute disseminated encephalomyelitis; myelin; autoantibody; antigen; array; diagnosis; biomarker; immunoglobulin; IgG; IgM
We identified three RORγt-specific inhibitors that suppress T helper 17 (Th17) cell responses including Th17 cell-mediated autoimmune disease. We systemically characterized RORγt binding in the presence and absence of drug with corresponding whole-genome transcriptome sequencing. RORγt acts both as a direct activator of Th17 cell signature genes and as a direct repressor of signature genes from other T-cell lineages, with the strongest transcriptional effects on cis-regulatory sites containing the RORα binding motif. RORγt is central in a densely interconnected regulatory network that shapes the balance of T-cell differentiation. The three inhibitors identified here modulated the RORγt-dependent transcriptional network to varying extents and through distinct mechanisms. Whereas one inhibitor displaced RORγt from its target-loci, the two more potent inhibitors affected transcription predominantly without removing DNA-binding. Our work illustrates the power of a system-scale analysis of transcriptional regulation to characterize potential therapeutic compounds that inhibit pathogenic Th17 cells and suppress autoimmunity.
Foxp3+ T regulatory (Treg) cells regulate immune responses and maintain self-tolerance. Recent work shows that Treg cells are comprised of many subpopulations with specialized regulatory functions. Here we identified Foxp3+ T cells expressing the co-inhibitory molecule TIGIT as a distinct Treg cell subset that specifically suppresses pro-inflammatory T helper 1 (Th1) and Th17 cell, but not Th2 cell responses. Transcriptional profiling characterized TIGIT+ Treg cells as an activated Treg subset with high expression of Treg signature genes. Ligation of TIGIT on Treg cells induced expression of the effector molecule fibrinogen-like protein 2 (Fgl2), which promoted Treg cell-mediated suppression of T effector cell proliferation. In addition, Fgl2 was necessary to prevent suppression of Th2 cell cytokine production in a model of allergic airway inflammation. TIGIT expression therefore identifies a Treg cell subset that demonstrates selectivity for suppression of Th1 and Th17 cell but not Th2 cell responses.
Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by autoimmune mediated demyelination and neurodegeneration. The CNS of patients with MS harbors expanded clones of antigen-experienced B cells that reside in distinct compartments including the meninges, cerebrospinal fluid (CSF) and parenchyma. It is not understood whether this immune infiltrate initiates its development in the CNS or in peripheral tissues. B cells in the CSF can exchange with those in peripheral blood, implying that CNS B cells may have access to lymphoid tissue that may be the specific compartment(s) in which CNS resident B cells encounter antigen and experience affinity maturation. In this study, paired tissues were used to determine whether the B cells that populate the CNS mature in the draining cervical lymph nodes (CLNs). High-throughput sequencing of the antibody repertoire demonstrated that clonally expanded B cells were present in both compartments. Founding members of clonal families were more often found in the draining CLNs. More mature clonal family members derived from these founders were observed in the draining CLNs and also in the CNS, including lesions. These data provide new evidence that B cells traffic freely across the tissue barrier with the majority of B cell maturation occurring outside of the CNS in the secondary lymphoid tissue. Our study may aid in further defining the mechanisms of immunomodulatory therapies that either deplete circulating B cells or impact the intrathecal B cell compartment by inhibiting lymphocyte transmigration into the CNS.
Developed societies, although having successfully reduced the burden of infectious disease, constitute an environment where metabolic, cardiovascular, and autoimmune diseases thrive. Living in westernized countries has not fundamentally changed the genetic basis on which these diseases emerge, but has strong impact on lifestyle and pathogen exposure. In particular, nutritional patterns collectively termed the “Western diet”, including high-fat and cholesterol, high-protein, high-sugar, and excess salt intake, as well as frequent consumption of processed and ‘fast foods’, promote obesity, metabolic syndrome, and cardiovascular disease. These factors have also gained high interest as possible promoters of autoimmune diseases. Underlying metabolic and immunologic mechanisms are currently being intensively explored. This review discusses the current knowledge relative to the association of “Western diet” with autoimmunity, and highlights the role of T cells as central players linking dietary influences to autoimmune pathology.
Western diet; Autoimmune diseases; Autoimmunity; Obesity; Sodium; Inflammatory; Gut microbiome; T cell regulation
T cells; environment; metabolism; microbiome; vitamin D; regulatory T cells; pathogens
We set out to characterize the clinical impact and functional consequences of rs1800693G, the multiple sclerosis (MS) susceptibility allele found in the TNFRSF1A locus.
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 rs1800693G and a second risk allele, R92Q, on immune function.
In 772 patients with MS, we see no evidence that rs1800693G strongly influences clinical or radiographic indices of disease course and treatment response; thus, rs1800693G 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, rs1800693G 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.
The MS rs1800693G 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.
CD4+ T helper cells are a central element of the adaptive immune system. They protect the organism against a wide range of pathogens and are able to initiate and control many immune reactions in combination with other cells of the adaptive and the innate immune system. Starting from a naïve cell, CD4+ T cells can differentiate into various effector cell populations with specialized function. This subset specific differentiation depends on numerous signals and the strength of stimulation. However, recent data have shown that differentiated CD4+ T cell subpopulations display a high grade of plasticity and that their initial differentiation is not an endpoint of T cell development. In particular, FoxP3+ regulatory T cells (Treg) and Th17 effector T cells demonstrate a high grade of plasticity, which allow a functional adaptation to various physiological situations during an immune response. However, the plasticity of Treg and Th17 cells might also be a critical factor for autoimmune disease. Here we discuss the recent developments in CD4+ T cell plasticity with a focus on Treg and Th17 cells and its role in human autoimmune disease, in particular multiple sclerosis (MS).
Autoimmunity; CD4+ T cells; IL-17; Th17; FoxP3; Treg; T cell plasticity
CD226 costimulatory signals strongly promote Th1 differentiation enhancing IFNγ production by naïve T cells. We recently reported that knockdown of CD226 on human T cells resulted in a decrease in T-bet and IFNγ expression. However, the role of CD226 on Th2 and Th17 cells remains unknown. Here, we found that CD226 and its ligand CD155 were decreased on Th2-polarized naïve T cells whereas both were highly expressed under Th17 conditions. Most IFNγ 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 partially contributes to IL-17 production but is dispensable for Th17 cell generation. In line with these results, CD226 blockade with neutralizing antibodies efficiently inhibited T cell activation, proliferation and production of IFNγ and IL-17 whereas IL-13 secretion remained functional. Taken together, our results establish an important role for CD226 in differentially regulating the pro-inflammatory (Th1/Th17)/anti-inflammatory (Th2) balance, suggesting that the CD226/CD155 interaction could potentially be targeted in therapeutic approaches to human autoimmune diseases.
To profile the reactivity of CSF-derived immunoglobulin from patients with multiple sclerosis (MS) against a large panel of antigens, to identify disease-specific reactivities.
CSF from subjects with MS with elevated immunoglobulin G and CSF from control subjects presenting with other inflammatory neurologic disease were screened against a protein array consisting of 9,393 proteins. Reactivity to a candidate protein identified using these arrays was confirmed with ELISA and immunocytochemistry.
Autoantibodies against one protein on the array, recombination signal binding protein for immunoglobulin kappa J region (RBPJ), discriminated between patients with MS and controls (p = 0.0052). Using a large validation cohort, we found a higher prevalence of autoantibodies against RBPJ in the CSF of patients with MS (12.5%) compared with the CSF of patients with other neurologic diseases (1.6%; p = 0.02) by ELISA. This difference in reactivity was restricted to the CSF as serum reactivity against RBPJ did not differ between patients and controls. The presence of CSF autoantibodies against RBPJ was further confirmed by immunocytochemistry.
These data indicate that RBPJ, a ubiquitous protein of the Notch signaling pathway that plays an important role in Epstein-Barr virus infection, is a novel MS autoantigen candidate that is recognized by CSF-derived immunoglobulin G in a subset of patients with MS.
Little is known about how human genetic variation affects the responses to environmental stimuli in the context of complex diseases. Experimental and computational approaches were applied to determine the effects of genetic variation on the induction of pathogen-responsive genes in human dendritic cells. We identified 121 common genetic variants associated in cis with variation in expression responses to E. coli lipopolysaccharide, influenza or interferon-β (IFNβ). We localized and validated causal variants to binding sites of pathogen-activated STAT and IRF transcription factors. We also identified a common variant in IRF7 that is associated in trans with type I interferon induction in response to influenza infection. Our results reveal common alleles that explain inter-individual variation in pathogen sensing and provide functional annotation for genetic variants that alter susceptibility to inflammatory diseases.
The immunosuppressive effects of CD4+ CD25high regulatory T cells interfere with anti-tumor immune responses in cancer patients. Here, we present a novel class of engineered human Interleukin (IL)-2 analogues that antagonize the IL-2 receptor, for inhibiting regulatory T cell suppression. These antagonists have been engineered for high affinity to the α subunit of the IL-2 receptor and very low affinity to either the β or γ subunit, resulting in a signaling-deficient IL-2 analogue that sequesters the IL-2 receptor α subunit from wild type IL-2. Two variants, “V91R” and “Q126T” with residue substitutions that disrupt the β and γ subunit binding interfaces, respectively, have been characterized in both a T cell line and in human primary regulatory T cells. These mutants retain their high affinity binding to IL-2 receptor α subunit, but do not activate STAT5 phosphorylation or stimulate T cell growth. The two mutants competitively antagonize wild-type IL-2 signaling through the IL-2 receptor with similar efficacy, with inhibition constants of 183 pM for V91R and 216 pM for Q126T. Here, we present a novel approach to CD25-mediated Treg inhibition, with the use of an engineered human IL-2 analogue that antagonizes the IL-2 receptor.
Interleukin-2; regulatory T cells; antagonist engineering; cytokine engineering
In biomedical applications, an experimenter encounters different potential sources of variation in data such as individual samples, multiple experimental conditions, and multivariate responses of a panel of markers such as from a signaling network. In multiparametric cytometry, which is often used for analyzing patient samples, such issues are critical. While computational methods can identify cell populations in individual samples, without the ability to automatically match them across samples, it is difficult to compare and characterize the populations in typical experiments, such as those responding to various stimulations or distinctive of particular patients or time-points, especially when there are many samples. Joint Clustering and Matching (JCM) is a multi-level framework for simultaneous modeling and registration of populations across a cohort. JCM models every population with a robust multivariate probability distribution. Simultaneously, JCM fits a random-effects model to construct an overall batch template – used for registering populations across samples, and classifying new samples. By tackling systems-level variation, JCM supports practical biomedical applications involving large cohorts. Software for fitting the JCM models have been implemented in an R package EMMIX-JCM, available from http://www.maths.uq.edu.au/~gjm/mix_soft/EMMIX-JCM/.
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.
Using the ImmunoChip custom genotyping array, we analysed 14,498 multiple sclerosis subjects and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (p-value < 1.0 × 10-4). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 multiple sclerosis subjects and 26,703 healthy controls. In these 80,094 individuals of European ancestry we identified 48 new susceptibility variants (p-value < 5.0 × 10-8); three found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants in 103 discrete loci outside of the Major Histocompatibility Complex. With high resolution Bayesian fine-mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalogue of multiple sclerosis risk variants and illustrates the value of fine-mapping in the resolution of GWAS signals.
Multiple sclerosis (MS) is an organ-specific autoimmune disorder that is in part genetically determined. The gene encoding the α-chain of the IL-2 receptor, IL2RA, harbors alleles associated with risk to MS and other autoimmune diseases. In addition, IL2RA genetic variants correlate with the levels of a soluble form of the IL-2 receptor in subjects with type 1 diabetes and multiple sclerosis. Here, we show that the IL2RA genotypes differentially affects soluble IL-2RA (sIL-2RA) levels in MS cases vs healthy controls; the two variants associated with MS (rs12722489 and rs2104286) account for 15 and 18% of the total variance in log10-transformed sIL-2RA concentration in control subjects but less so in subjects with MS (2 and 5%), suggesting that perturbations associated with disease or treatment may influence sIL-2RA levels in subjects with MS. Whereas analyses demonstrate that sIL-2RA serum concentrations are a remarkably stable phenotype in both healthy controls and untreated MS subjects, a difference is observed between benign and malignant MS. These data indicate that, in addition to specific allelic variants at IL2RA, immunological perturbations associated with aggressive forms of the disease can influence sIL-2RA levels in serum of MS subjects. We also demonstrate, functionally, that sIL-2RA can inhibit IL-2 signaling, yet enhance T cell proliferation and expansion. In summary, we propose that before disease onset, strong genetic factors associated with disease risk dictate sIL-2RA levels that may be further modulated with onset of chronic systemic inflammation associated with MS.
Autoimmune disease results from a loss of tolerance to self-antigens in genetically susceptible individuals. Completely understanding this process requires that targeted antigens be identified, and so a number of techniques have been developed to determine immune receptor specificities. We previously reported the construction of a phage-displayed synthetic human peptidome and a proof-of-principle analysis of antibodies from three patients with neurological autoimmunity. Here we present data from a large-scale screen of 298 independent antibody repertoires, including those from 73 healthy sera, using phage immunoprecipitation sequencing. The resulting database of peptide-antibody interactions characterizes each individual’s unique autoantibody fingerprint, and includes specificities found to occur frequently in the general population as well as those associated with disease. Screening type 1 diabetes (T1D) patients revealed a prematurely polyautoreactive phenotype compared with their matched controls. A collection of cerebrospinal fluids and sera from 63 multiple sclerosis patients uncovered novel, as well as previously reported antibody-peptide interactions. Finally, a screen of synovial fluids and sera from 64 rheumatoid arthritis patients revealed novel disease-associated antibody specificities that were independent of seropositivity status. This work demonstrates the utility of performing PhIP-Seq screens on large numbers of individuals and is another step toward defining the full complement of autoimmunoreactivities in health and disease.
autoantigen discovery; high throughput screening; PhIP-Seq; proteomics
The major histocompatibility complex (MHC) region is strongly associated with multiple sclerosis (MS) susceptibility. HLA-DRB1*15:01 has the strongest effect, and several other alleles have been reported at different levels of validation. Using SNP data from genome-wide studies, we imputed and tested classical alleles and amino acid polymorphisms in 8 classical human leukocyte antigen (HLA) genes in 5,091 cases and 9,595 controls. We identified 11 statistically independent effects overall: 6 HLA-DRB1 and one DPB1 alleles in class II, one HLA-A and two B alleles in class I, and one signal in a region spanning from MICB to LST1. This genomic segment does not contain any HLA class I or II genes and provides robust evidence for the involvement of a non-HLA risk allele within the MHC. Interestingly, this region contains the TNF gene, the cognate ligand of the well-validated TNFRSF1A MS susceptibility gene. The classical HLA effects can be explained to some extent by polymorphic amino acid positions in the peptide-binding grooves. This study dissects the independent effects in the MHC, a critical region for MS susceptibility that harbors multiple risk alleles.
Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease with a heritable component. Although it has been known for a long time that the strongest MS risk factor maps to the major histocompatibility complex (MHC) on chromosome 6, there are still many unresolved questions as to the identity and the nature of the risk variants within the MHC. Because the MHC has a complex structure, systematic investigation across this region has been challenging. In this study, we used state-of-the-art imputation methods coupled to statistical regression to query variants in the human leukocyte antigen (HLA) class I and II genes for a role in MS risk. Starting from available SNP genotype data, we replicated the strongest risk factor, the HLA-DRB1*15:01 allele, and were able to identify 11 independent effects in total. Functional studies are now needed to understand their mechanism in MS etiology.
The ubiquitous protein CD46, a regulator of complement activity, promotes T cell activation and differentiation towards a regulatory Tr1-like phenotype. CD46-mediated differentiation pathway is defective in several chronic inflammatory diseases, underlying the importance of CD46 in controlling T cell function and the need to understand its regulatory mechanisms. Using an RNAi-based screening approach in primary T cells, we have identified that two members of the G-protein coupled receptor (GPCR) kinases were involved in regulating CD46 expression at the surface of activated cells. We have investigated the role of prostaglandin E2 (PGE2), which binds to the E-prostanoid family of GPCRs through four subtypes of receptors called EP1-4, in the regulation of CD46 expression and function. Conflicting roles of PGE2 in T cell functions have been reported, and the reasons for these apparent discrepancies are not well understood. We show that addition of PGE2 strongly downregulates CD46 expression in activated T cells. Moreover, PGE2 differentially affects T cell activation, cytokine production and phenotype depending on the activation signals received by the T cells. This was correlated with a distinct pattern of the PGE2 receptors induced, with EP4 being preferentially induced by CD46 activation. Indeed, addition of an EP4 antagonist could reverse the effects observed on cytokine production observed following CD46 costimulation. These data demonstrate a novel role of the PGE2-EP4-GRK axis in CD46 functions, which might at least partly explain the diverse roles of PGE2 in T cell functions.