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The article explores autoimmune encephalitis, a condition where the immune system attacks the brain. It emphasizes the role of B cells in the development of autoantibodies, which are responsible for the disease. The authors studied immune cells from patients with anti-LGI1 and anti-CASPR2 encephalitis and found an abundance of plasma cells that produce the autoantibodies. They also discuss the interaction between T cells and B cells in the activation and expansion of B cells. The article suggests that B cells may be activated outside of the central nervous system and cross the blood-brain barrier to produce autoantibodies. It mentions the potential for B cell-targeted therapies in treating autoimmune diseases, but the specific antigens recognized by T cells in autoimmune encephalitis remain unknown. [Extracted from the article]

C‐type lectin‐like CD161, a class II transmembrane protein, is a surface receptor expressed by NK cells and T cells. In coeliac disease, CD161 was expressed more frequently on gluten‐reactive CD4 + T cells compared to other memory CD4 + T cells isolated from the same tissue compartment. CD161 is a putative co‐signalling molecule that was proposed to act as co‐stimulatory receptor in the context of signalling through TCR, but contradicting results were published. In order to understand the role of CD161 in gluten‐reactive CD4 + T cells, we combined T cell stimulation assays or T cell proliferation assays with ligation of CD161 and intracellular cytokine staining. We found that CD161 ligation provided neither co‐stimulatory nor co‐inhibitory signals to modulate proliferation and IFN‐γ or IL‐21 production by gluten‐reactive CD4 + T cell clones. Thus, we suggest that CD161 does not function as a co‐signalling receptor in the context of gluten‐reactive CD4 + T cells. [ABSTRACT FROM AUTHOR]

Celiac disease is caused by an abnormal intestinal T cell response to cereal gluten proteins. The disease has a strong human leukocyte antigen (HLA) association, and CD4+ T cells recognizing gluten epitopes presented by disease-associated HLA-DQ allotypes are considered to be drivers of the disease. This paper provides an update of the currently known HLA-DQ restricted gluten T cell epitopes with their names and sequences. [ABSTRACT FROM AUTHOR]

Erik failed to raise HLA-specific rabbit antibodies, which could help to identify donor-recipient pairs bearing compatible HLA molecules. Erik became a world expert in this field producing key papers on the HLA association of type 1 diabetes,12 multiple sclerosis13 and coeliac disease.14,15 We were all fortunate to collaborate with Erik on different aspects of HLA biology, ranging from organ transplantation to the molecular underpinnings of HLA association in coeliac disease. From one of the volunteers, Erik collected serum which identified the antigen MH,3 later baptized HLA-B5. GLO:2CR/01jul21:sji13055-fig-0001.jpg PHOTO (COLOR): . gl Erik Thorsby, one of the true pioneers in the fields of HLA, immunogenetics and transplantation immunology, passed away on March 23rd. [Extracted from the article]

From one of the volunteers Erik collected serum which identified the antigen MH (Thorsby and Kissmeyer-Nielsen [14]), later baptised HLA-B5. We were all fortunate to collaborate with Erik on different aspects of HLA biology, ranging from organ transplantation to the molecular underpinnings of HLA-association in coeliac disease. Graph Erik Thorsby, one of the true pioneers in the fields of HLA, immunogenetics and transplantation immunology passed away on March 23rd. Erik failed to raise HLA specific rabbit antibodies, which could help to identify donor-recipient pairs bearing compatible HLA-molecules. [Extracted from the article]

Celiac disease is a chronic inflammatory condition of the small intestine caused by aberrant adaptive immune response to gluten protein from wheat and related cereal plants. Over 90% of celiac disease patients carry the HLA-DQ2.5 allotype and HLA-DQ2.5 presents gluten peptides to gluten-reactive CD4+ T cells in celiac disease patients. A large number of HLA-DQ2.5-restricted gluten T cell epitopes have been identified over the years. These epitopes are in general proline-rich and contain at least one glutamic acid residue that is generated from glutamine in the native gluten protein by deamidation. The deamidation is mediated by the enzyme transglutaminase 2 (TG2). It has been shown that the same T cell could recognize several different HLA-DQ2.5-restricted gluten T cell epitopes due to sequence similarities. In this paper, we demonstrate that three T cell clones derived from duodenal biopsies of different celiac disease patients are able to respond to at least five different gluten T cell epitopes within the DQ2.5-glia-γ4 epitope family, including two novel epitopes. [ABSTRACT FROM AUTHOR]

Celiac disease is a human T cell-mediated autoimmunelike disorder caused by exposure to dietary gluten in genetically predisposed individuals. This review will discuss how CD4 T cell responses directed against an exogenous Ag can cause an autoreactive B cell response and participate in the licensing of intraepithelial lymphocytes to kill intestinal epithelial cells. Furthermore, this review will examine the mechanisms by which intraepithelial cytotoxic T cells mediate tissue destruction in celiac disease. [ABSTRACT FROM AUTHOR]

It will soon be 50 years since the first MHC associations with human disease were described. These seminal studies opened a flourishing area of research, yet much remains to be discovered. Genome-wide association studies of autoimmune diseases have demonstrated that the MHC region has effect sizes that supersede those for any non-MHC locus for most diseases. Thus, an understanding of how particular MHC alleles confer susceptibility will be essential for a comprehensive understanding of autoimmune disease pathogenesis. Here we review recent exciting findings in this important field. [ABSTRACT FROM AUTHOR]

Abstract: Secretion of cytokines by T cells in vitro can be influenced by the methods chosen for T cell activation. However, the awareness of this fact appears insufficient. Two of the most widely applied methods for activation of T cells are phorbol 12-myristate 13-acetate (PMA) together with Ionomycin or anti-CD3/anti-CD28 stimulation. We analyzed production of IL-4, IFN-γ, IL-17 and IL-10 by a panel of human CD4 T-cell clones isolated from intestinal biopsies using the Bio-Plex™ assay and also flow-cytometry for the latter three cytokines. Higher levels of IL-17 and IFN-γ were produced by stimulation with PMA/Ionomycin compared to anti-CD3/anti-CD28. Some T-cell clones which were assigned to produce both cytokines by stimulation with PMA/Ionomycin, were only assigned to produce IFN-γ by anti-CD3/anti-CD28 stimulation. IL-10 production was higher after anti-CD3/anti-CD28 stimulation. Furthermore the dose response curve for PMA/Ionomycin differed for IL-10 compared to IL-17 and IFN-γ as it was biphasic with no IL-10 production at higher PMA/Ionomycin concentrations. These results demonstrated that the cytokine profile may be differently determined depending on the assay and conditions used and illustrate that care should be taken when designing and interpreting studies of cytokine production by T cells. [Copyright &y& Elsevier]

Coeliac disease, an inflammatory disease of the small intestine, shares key features with autoimmune disorders, such as susceptibility genes, presence of autoantibodies and T cell-mediated destruction of specific cells. Strikingly, however, continuous exposure to the exogenous dietary antigen gluten and gluten-specific adaptive immunity are required to maintain immunopathology. These observations challenge the notion that autoimmunity requires adaptive immune activation towards self antigens. Using coeliac disease as an example, we propose that other exogenous factors might be identified as drivers of autoimmune processes, in particular when evidence for T cells with specificity for self antigens driving the disease is lacking. [ABSTRACT FROM AUTHOR]

Posttranslational modification (PTM) of antigen is a way to break T-cell tolerance to self-antigens and promote autoimmunity. However, the precise mechanisms by which modifications would facilitate autoimmune T-cell responses and how they relate to particular autoimmune-associated MHC molecules remain elusive. Celiac disease is a T-cell mediated enteropathy with a strong HLA association where the immune response is directed mainly against deamidated cereal gluten peptides that have been modified by the enzyme transglutaminase 2. The disease is further characterized by autoantibodies to transglutaminase 2 that have extraordinary high disease specificity and sensitivity. There have been important advances in the knowledge of celiac disease pathogenesis, and these insights may be applicable to other autoimmune disorders where PTM plays a role. This insight gives clues for understanding the involvement of PTMs in other autoimmune diseases. [Copyright &y& Elsevier]

Celiac disease (CD) is a gluten-sensitive enteropathy that develops in genetically susceptible individuals by exposure to cereal gluten proteins. This review integrates insights from immunological studies with results of recent genetic genome-wide association studies into a disease model. Genetic data, among others, suggest that viral infections are implicated and that natural killer effector pathways are important in the pathogenesis of CD, but most prominently these data converge with existing immunological findings that CD is primarily a T cell--mediated immune disorder in which CD4++ T cells that recognize gluten peptides in the context of major histocompatibility class II molecules play a central role. Comparison of genetic pathways as well as genetic susceptibility loci between CD and other autoimmune and inflammatory disorders reveals that CD bears stronger resemblance to T cell--mediated organ-specific autoimmune than to inflammatory diseases. Finally, we present evidence suggesting that the high prevalence of CD in modern societies may be the by-product of past selection for increased immune responses to combat infections in populations in which agriculture and cereals were introduced early on in the post-Neolithic period. [ABSTRACT FROM AUTHOR]

Coeliac disease is an inflammatory disorder with autoimmune features that is characterized by destruction of the intestinal epithelium and remodelling of the intestinal mucosa following the ingestion of dietary gluten. A common feature of coeliac disease and many organ-specific autoimmune diseases is a central role for T cells in causing tissue destruction. In this Review, we discuss the emerging hypothesis that, in coeliac disease, intestinal tissue inflammation--induced either by infectious agents or by gluten--is crucial for activating T cells and eliciting their tissue-destructive effector functions. [ABSTRACT FROM AUTHOR]

Celiac disease is caused by an inappropriate immune response to ingested gluten proteins. As a dietary antigen, gluten undergoes extensive but incomplete proteolytic digestion in the intestinal lumen. The resultant peptide fragments of gluten require deamidation, but not necessarily further intracellular processing for presentation. Recent studies reveal why the disease associated HLA-DQ2 molecule is particularly suited for binding proline-rich gluten peptides. In comparison, DQ8 exhibits different binding characteristics, which may explain the lesser risk for disease in association with this molecule. [Copyright &y& Elsevier]

The article discusses the new genetic findings that will set the stage for future development of animal models in inflammatory bowel disease (IBD). It is said that the new models will be created to understand the function of the novel IBD genes. Results from the studies of NOD2 gene in mice suggest that the development of adequate models will not be straightforward.

The article focuses on a study which reveals that exogenous gluten drives T cell–B cell interactions that cause autoimmunity in celiac disease. It mentions that the gluten epitopes that are recognized by the CD4+ T cells uniformly contain negatively charged glutamate residues that are important for binding to the CeD-associated major histocompatibility complex (MHC) class II molecules.

Identifying novel genes and pathways controlling T-cell activation holds the promise of developing novel therapies for autoimmune disease and cancer. Recent advances in the human genome project have shown that it is timely for small groups searching for this Holy Grail to rethink their options. In this review, some alternative strategies employed in pursuing novel disease pathways in rodents and humans, including recent results, are presented. Examples include the murine Roquin and Ncf1 genes, and the PTPN22 gene identified in humans. The potential benefit of reducing the heterogeneity of clinically defined diseases by the careful phenotyping of patients, cells and lesions using advanced molecular biology and imaging techniques is highlighted. [Copyright &y& Elsevier]

Major advances have been made in the molecular understanding of coeliac disease, initiated by the identification of intestinal gluten-reactive T cells. It is now clear that this common intestinal disorder, which is precipitated by the ingestion of wheat gluten, is mediated by DQ2-restricted T cells specific for gluten peptides modified by transglutaminase 2, the same enzyme that is targeted by disease-specific autoantibodies. Interestingly, many of the important features identified in coeliac disease, including HLA association, target organ T-cell infiltration, disease-specific autoantibodies and the distinct targeting of in vivo modified antigens, are also present in rheumatoid arthritis. The experiences from coeliac disease should therefore help identify disease-relevant T-cell epitopes in rheumatoid arthritis. [Copyright &y& Elsevier]

Celiac disease, which results from an immune reaction to ingested cereal gluten proteins, has several autoimmune features. In particular, celiac disease patients produce highly disease specific IgA and IgG autoantibodies to tissue transglutaminase when they are on a gluten-containing diet, and they have small intestinal intraepithelial lymphocytes which can mediate direct cytotoxicity of enterocytes expressing MIC molecules in an antigen non-specific manner. Similar to typical autoimmune disorders, celiac disease has a multifactorial aetiology with complex genetics, and several autoimmune diseases are commonly presented by patients with celiac disease. Much has been learned about the immunology of celiac disease in recent years, and there is overwhelming evidence that the immune response to gluten is central to the pathogenesis. In light of this, the many autoimmune phenomena associated with celiac disease are thought-provoking, and they challenge us to rethink the boundaries between autoimmunity and immunopathology. [Copyright &y& Elsevier]

HLA-DQ2 predisposes an individual to celiac sprue by presenting peptides from dietary gluten to intestinal CD4+ T cells. A selectively deamidated multivalent peptide from gluten (LQLQPF- PQP&Edline;LPYPQP&Edline;LPYPQP&Edline;LPYPQPQPF; underlined residues correspond to posttranslational Q → E alterations) is a potent trigger of DQ2 restricted T cell proliferation. Here we report equilibrium and kinetic measurements of interactions between DQ2 and (i) this highly immunogenic multivalent peptide, (ii) its individual constituent epitopes, (iii) its nondeamidated precursor, and (iv) a reference high-affinity ligand of HLA-DQ2 that is not recognized by gluten-responsive I cells from celiac spite patients. The deamidated 33-mer peptide efficiently exchanges with a preloaded peptide in the DQ2 ligand-binding groove at pH 5.5 as well as pH 7.3, suggesting that the peptide can be presented to T cells comparably well through the endocytic pathway or via direct loading onto extracellular HLA-DQ2. In contrast, the monovalent peptides, and the nondeamidated precursor, as well as the tight-binding reference peptide show a much poorer ability to exchange with a preloaded peptide in the DQ2 binding pocket, especially at pH 7.3, suggesting that endocytosis of these peptides is a prerequisite for T cell presentation. At pH 5.5 and 7.3, dissociation of the deamidated 33-mer peptide from DQ2 is much slower than dissociation of its constituent monovalent epitopes or the nondeamidated precursor but faster than dissociation of the reference high-affinity peptide. Oligomeric states involving multiple copies of the DQ2 heterodimer bound to a single copy of the multivalent 33-mer peptide are not observed. Together, these results suggest that the remarkable antigenicity of the 33-mer gluten peptide is primarily due to its unusually efficient ability to displace existing ligands in the HLA-DQ2 binding pocket, rather than an extremely low rate of dissociation. [ABSTRACT FROM AUTHOR]

The disease mechanisms of complex inflammatory disorders are difficult to define because of extensive interactions between genetic and environmental factors. Coeliac disease is a typical complex inflammatory disorder, but this disease is unusual in that crucial genetic and environmental factors have been identified. This knowledge has allowed functional studies of the predisposing HLA molecules, the identification of antigenic epitopes and detailed studies of disease-relevant T cells in coeliac disease. This dissection of the pathogenic mechanisms of coeliac disease has uncovered principles that are relevant to other chronic inflammatory diseases. [ABSTRACT FROM AUTHOR]

Provides information on celiac diseases (CD), an intestinal disorder with multifactorial etiology. Clinical manifestations of CD; Genetic aspect of the disease; Mechanisms involved in the formation of celiac lesion.

The article discusses a research on how some T cells become dangerous by taking on the characteristics of natural killer cells. It references a study by B. Meresse and colleagues in the previous issue of the "Journal of Experimental Medicine." It has been suggested that some T cells can appear with recognition receptors normally found only on natural killer cells. The acquisition of activating receptors allows the T cells to proliferate, kill, and secrete cytokines without engagement of the T cell receptor, which has therapeutic implications for celiac disease.

Infiltration of lymphocytes in the small intestinal epithelium is a hallmark of active celiac disease. In this issue of Immunity, two papers uncover mechanisms controlling the cytolytic potential of these cells and provide evidence that lymphocyte killing of enterocytes is an important part of the celiac disease pathogenesis. [Copyright &y& Elsevier]

Dermatitis herpetiformis (DH) is an inflammatory skin disorder often considered as an extra intestinal manifestation of celiac disease (CeD). Hallmarks of CeD and DH are auto‐antibodies to transglutaminase 2 (TG2) and transglutaminase 3 (TG3), respectively. DH patients have auto‐antibodies reactive with both transglutaminase enzymes. Here it is reported that in DH both gut plasma cells and serum auto‐antibodies are specific for either TG2 or TG3 with no TG2–TG3 cross reactivity. By generating monoclonal antibodies from TG3‐specific duodenal plasma cells of DH patients, three conformational epitope groups are defined. Both TG2‐specific and TG3‐specific gut plasma cells have few immunoglobulin (Ig) mutations, and the two transglutaminase‐reactive populations show distinct selection of certain heavy and light chain V‐genes. Mass spectrometry analysis of TG3‐specific serum IgA corroborates preferential usage of IGHV2‐5 in combination with IGKV4‐1. Collectively, these results demonstrate parallel induction of anti‐TG2 and anti‐TG3 auto‐antibody responses involving separate B‐cell populations in DH patients. [ABSTRACT FROM AUTHOR]

Background: Formation of complexes between transglutaminase 2 (TG2) and gluten can mechanistically explain why TG2 serves both as B-cell autoantigen and as an enzyme that creates deamidated gluten epitopes in coeliac disease (CeD). A model has been proposed where TG2 released from shed epithelial cells encounters high concentrations of dietary gluten peptides to form these TG2:gluten complexes. In this work we have characterised TG2 protein expression in gut epithelial cells in humans. Methods: Western blot analysis, immunofluorescence staining and mass spectrometry in combination with laser capture microdissection to gain spatial resolution were used to characterise TG2 expression in the epithelial cell layer of healthy and coeliac disease affected duodenum. Findings: TG2 is expressed in human duodenal epithelial cells, including cells in the apical region that are shed into the gut lumen. In untreated CeD the apical expression of TG2 is doubled. Enzymatically active TG2 is readily released from isolated human intestinal epithelial cells. Conclusion: Shed epithelial cells are a plausible source of pathogenic TG2 enzyme in CeD. Increased epithelial TG2 expression and increased epithelial shedding in active CeD may reinforce action of luminal TG2 in this condition. [ABSTRACT FROM AUTHOR]

An abstract of the conference paper "Coeliac disease: the showcase of interaction between genes, environment and immunology in chronic tissue inflammation," by Ludvig M. Sollid is presented.

Discusses coeliac disease, which is caused by inappropriate immune response to dietary wheat gluten and similar proteins in rye and barley. Genes which may contribute to disease development; How most lesion-derived T cells recognize gluten peptides that are modified by the enzyme transglutaminase.

The article discusses a research study conducted to combine the knowledge of a distinct phenotype of gluten-reactive T cells and key features of known gluten epitopes for the discovery of unknown epitopes. It is noted that the research tested 42 wheat gluten–reactive T cell clones, isolated on the basis of distinct phenotype and with no reactivity to known epitopes, against synthetic peptides bioinformatically identified from a wheat gluten protein database.

• A high capacity anti-transglutaminase 2 IgA and IgG assay is possible. • Anti-transglutaminase 2 IgA and IgG could be used in population screening. • Anti-transglutaminase 2 IgA levels correlates with disease severity. The aim of the present study was to develop and clinically validate a high-throughput assay for serum IgA and IgG antibodies against transglutaminase-2 (TG2) and to determine appropriate assay cut-offs for large-scale population screening for celiac disease. An automated method was developed using dual label time-resolved fluorometry on the AutoDELFIA platform. Individuals (n = 1920) from the general population were screened. Subjects with serum anti-TG2 concentrations above a preliminary cut-off (>0.3 mg*/L anti-TG2 IgA or >0.5 mg*/L anti-TG2 IgG) were offered endoscopic examination and biopsy. A diagnosis of celiac disease was given if villous atrophy (Marsh grade 3) was found. The assay had a limit of quantification of 0.25 mg*/L (anti-TG2 IgA) and 0.60 mg*/L (anti-TG2 IgG) with imprecision (CV) < 16% and <18% respectively. A total of 66 individuals were above the preliminary cut-off, and 56 underwent endoscopy. Of these, 26 were diagnosed with celiac disease. Sixty-eight percent of subjects with anti-TG2 IgA ≥ 0.7 mg*/L or anti-TG2 IgG ≥ 1.0 mg*/L had biopsy-proven celiac disease, and utilization of these higher cut-offs identified 96% of biopsy-positive patients. At the time of endoscopy, all individuals with anti-TG2 IgA > 2.0 mg*/L had celiac disease, and this cut-off identified 88% of newly diagnosed celiac patients. Eight percent (2/26) of the newly diagnosed patients had primarily anti-TG2 IgG. In this study we developed and clinically validated a robust and automated assay suitable for celiac disease screening in the general population. [ABSTRACT FROM AUTHOR]

Objective. The aim of this study was to assess the frequency of mycobacteria and Escherichia coli reactive T cells in intestinal biopsies from patients with Crohn's disease (CD) and ulcerative colitis (UC). Materials and methods. The biopsies were obtained by colonoscopy from adult patients with active CD ( n = 5) and active UC ( n = 4). The number of CD4+ T cell clones expanded and screened from each patient varied from 383 to 3972 giving a total of 16639 individual clones. The T cell clones were tested for responses to Mycobacterium avium subspecies paratuberculosis (MAP) and E. coli. The cytokine profile of 42 individual T cell clones from four CD patients was assessed. Results. The frequency of mycobacteria reactive T cell clones in CD patients ranged from 0.17 to 1.63% and was higher ( p = 0.038) than the frequency of E. coli reactive T cells ranging from 0 to 0.18%. No or very low numbers of mycobacteria reactive clones were detected in three UC patients while the fourth UC patient had a frequency similar to what was observed in CD patients. The frequencies of E. coli reactive T cell clones in UC patients ranged from 0 to 0.52%. T cell clones ( n = 42) from CD patients all produced IL-17 and/or IFN-γ. Several clones were also able to produce IL-10. Conclusions. The high frequency of intestinal tissue resident T cells reactive to mycobacteria suggests that an adaptive immune response have taken place and argues that these bacteria may contribute to the chronic inflammation in CD. [ABSTRACT FROM AUTHOR]

Many antibody responses induced by infection, vaccination or autoimmunity show signs of convergence across individuals with epitope-dependent selection of particular variable region gene segments and complementarity determining region 3 properties. However, not much is known about the relationship between antigen-specific effector cells and antigen-specific precursors present in the naïve B-cell repertoire. Here, we sought to address this relationship in the context of celiac disease, where there is a stereotyped autoantibody response against the enzyme transglutaminase 2 (TG2). By generating TG2-specific monoclonal antibodies from both duodenal plasma cells and circulating naïve B cells, we demonstrate a discord between the naïve TG2-specific repertoire and the cells that are selected for autoantibody production. Hence, the naïve repertoire does not fully reflect the epitope preference and gene usage observed for memory B cells and plasma cells. Instead, distinct naïve B cells that target particular TG2 epitopes appear to be selectively activated at the expense of TG2-binding B cells targeting other epitopes. [Display omitted] • Celiac disease autoantibodies show V gene- and CDR3-dependent targeting of epitopes. • Bias toward N-terminal epitopes is not explained by masking of C-terminal epitopes. • Autoreactive naïve B cells are present in healthy individuals and in celiac patients. • The naïve autoreactive repertoire does not mirror the disease effector repertoire. • Autoreactive B cells targeting particular epitopes are selectively activated. [ABSTRACT FROM AUTHOR]

Background: Celiac disease is an autoimmune enteropathy driven by dietary intake of gluten proteins. Typical histopathologic features are villous flattening, crypt hyperplasia and infiltration of inflammatory cells in the intestinal epithelium and lamina propria. The disease is hallmarked by the gluten-dependent production of autoantibodies targeting the enzyme transglutaminase 2 (TG2). While these antibodies are specific and sensitive diagnostic markers of the disease, a role in the development of the enteropathy has never been established. Methods: We addressed this question by injecting murine antibodies harboring the variable domains of a prototypic celiac anti-TG2 immunoglobulin into TG2-sufficient and TG2-deficient mice evaluating for celiac enteropathy. Results: We found no histopathologic abnormalities nor clinical signs of disease related to the injection of anti-TG2 IgG or IgA. Conclusions: Our findings do not support a direct role for secreted anti-TG2 antibodies in the development of the celiac enteropathy. [ABSTRACT FROM AUTHOR]

The pathogenic immune response in celiac disease (CeD) is orchestrated by phenotypically distinct CD4+ T cells that recognize gluten epitopes in the context of disease‐associated HLA‐DQ allotypes. Cells with the same distinct phenotype, but with elusive specificities, are increased across multiple autoimmune conditions. Here, whether sorting of T cells based on their distinct phenotype (Tphe cells) yields gluten‐reactive cells in CeD is tested. The method′s efficiency is benchmarked by parallel isolation of gluten‐reactive T cells (Ttet cells), using HLA‐DQ:gluten peptide tetramers. From gut biopsies of 12 untreated HLA‐DQ2.5+ CeD patients, Ttet+/Tphe+, Ttet−/Tphe+, and Ttet−/Tphe− cells are sorted for single‐cell T‐cell receptor (TCR)‐sequencing (n = 8) and T‐cell clone (TCC)‐generation (n = 5). The generated TCCs are TCR sequenced and tested for their reactivity against deamidated gluten. Gluten‐reactivity is observed in 91.2% of Ttet+/Tphe+ TCCs, 65.3% of Ttet−/Tphe+ TCCs and 0% of Ttet−/Tphe− TCCs. TCR sequencing reveals clonal expansion and sequence sharing across patients, features reflecting antigen‐driven responses. The feasibility to isolate antigen‐specific CD4+ T cells by the sole use of phenotypic markers in CeD outlines a potential avenue for characterizing disease‐driving CD4+ T cells in autoimmune conditions. [ABSTRACT FROM AUTHOR]

Celiac disease is a T cell-mediated chronic inflammatory condition often characterized by human leukocyte antigen (HLA)-DQ2.5 molecules presenting gluten epitopes derived from wheat, barley, and rye. Although some T cells exhibit cross-reactivity toward distinct gluten epitopes, the structural basis underpinning such cross-reactivity is unclear. Here, we investigated the T-cell receptor specificity and cross-reactivity of two immunodominant wheat gluten epitopes, DQ2.5-glia-α1a (PFPQPELPY) and DQ2.5-glia-ω1 (PFPQPEQPF). We show by surface plasmon resonance that a T-cell receptor alpha variable (TRAV) 4+-T-cell receptor beta variable (TRBV) 29-1+ TCR bound to HLA-DQ2.5-glia-α1a and HLA-DQ2.5-glia-ω1 with similar affinity, whereas a TRAV4- (TRAV9-2+) TCR recognized HLA-DQ2.5-glia-ω1 only. We further determined the crystal structures of the TRAV4+-TRBV29-1+ TCR bound to HLA-DQ2.5-glia-α1a and HLA-DQ2.5-glia-ω1, as well as the structure of an epitope-specific TRAV9-2+-TRBV7-3+ TCRHLA- DQ2.5-glia-ω1 complex. We found that position 7 (p7) of the DQ2.5-glia-α1a and DQ2.5-glia-ω1 epitopes made very limited contacts with the TRAV4+ TCR, thereby explaining the TCR cross-reactivity across these two epitopes. In contrast, within the TRAV9-2+ TCR-HLA-DQ2.5-glia-ω1 ternary complex, the p7-Gln was situated in an electrostatic pocket formed by the hypervariable CDR3β loop of the TCR and Arg70β from HLA-DQ2.5, a polar network which would not be supported by the p7-Leu residue of DQ2.5-glia-α1a. In conclusion, we provide additional insights into the molecular determinants of TCR specificity and cross-reactivity to two closely-related epitopes in celiac disease. [ABSTRACT FROM AUTHOR]

Abstract: Transglutaminase 2 (TG2) catalyzes cross-linking or deamidation of glutamine residues in peptides and proteins. The in vivo deamidation of gliadin peptides plays an important role in the immunopathogenesis of celiac disease (CD). Although deamidation is considered to be a side-reaction occurring in the absence of suitable amines or at a low pH, a recent paper reported the selective deamidation of the small heat shock protein 20 (Hsp20), suggesting that deamidation could be a substrate dependent event. Here we have measured peptide deamidation and transamidation in the same reaction to reveal factors that affect the relative propensity for the two possible products. We report that the propensity for deamidation by TG2 is both substrate dependent and influenced by the reaction conditions. Direct deamidation is favored for poor substrates and at low concentrations of active TG2, while indirect deamidation (i.e. hydrolysis of transamidated product) can significantly contribute to the deamidation of good peptide substrates at higher enzyme concentrations. Further, we report for the first time that TG2 can hydrolyze iso-peptide bonds between two peptide substrates. This was observed also for gliadin peptides introducing a novel route for the generation of deamidated T cell epitopes in celiac disease. [Copyright &y& Elsevier]

TCR-like antibodies represent a unique type of engineered antibodies with specificity toward pHLA, a ligand normally restricted to the sensitive recognition by T cells. Here, we report a phage display-based sequential development path of such antibodies. The strategy goes from initial lead identification through in silico informed CDR engineering in combination with framework engineering for affinity and thermostability optimization, respectively. The strategy allowed the identification of HLA-DQ2.5 gluten peptide-specific TCR-like antibodies with low picomolar affinity. Our method outlines an efficient and general method for development of this promising class of antibodies, which should facilitate their utility including translation to human therapy. [ABSTRACT FROM AUTHOR]

A hallmark of celiac disease is the gluten-dependent production of antibodies specific for deamidated gluten peptides (DGP) and the enzyme transglutaminase 2 (TG2). Both types of antibodies are believed to result from B cells receiving help from gluten-specific CD4+ T cells and differentiating into antibody-producing plasma cells. We have here studied the collaboration between DGP- and TG2-specific B cells with gluten-specific CD4+ T cells using transgenic mice expressing celiac patient-derived T-cell and B-cell receptors, as well as between B-cell transfectants and patient-derived gluten-specific T-cell clones. We show that multivalent TG2-gluten complexes are efficient antigens for both TG2-specific and DGP-specific B cells and allow both types of B cells to receive help from gluten-specific T cells of many different specificities. [ABSTRACT FROM AUTHOR]

Gluten‐specific CD4+ T cells being drivers of celiac disease (CeD) are obvious targets for immunotherapy. Little is known about how cell markers harnessed for T‐cell‐directed therapy can change with time and upon activation in CeD and other autoimmune conditions. In‐depth characterization of gluten‐specific CD4+ T cells and CeD‐associated (CD38+ and CD103+) CD8+ and γδ+ T cells in blood of treated CeD patients undergoing a 3 day gluten challenge is reported. The phenotypic profile of gluten‐specific cells changes profoundly with gluten exposure and the cells adopt the profile of gluten‐specific cells in untreated disease (CD147+, CD70+, programmed cell death protein 1 (PD‐1)+, inducible T‐cell costimulator (ICOS)+, CD28+, CD95+, CD38+, and CD161+), yet with some markers being unique for day 6 cells (C‐X‐C chemokine receptor type 6 (CXCR6), CD132, and CD147) and with integrin α4β7, C‐C motif chemokine receptor 9 (CCR9), and CXCR3 being expressed stably at baseline and day 6. Among gluten‐specific CD4+ T cells, 52% are CXCR5+ at baseline, perhaps indicative of germinal‐center reactions, while on day 6 all are CXCR5−. Strikingly, the phenotypic profile of gluten‐specific CD4+ T cells on day 6 largely overlaps with that of CeD‐associated (CD38+ and CD103+) CD8+ and γδ+ T cells. The antigen‐induced shift in phenotype of CD4+ T cells being shared with other disease‐associated T cells is relevant for development of T‐cell‐directed therapies. [ABSTRACT FROM AUTHOR]

The article presents a study by J. Petersen and his colleagues which aims at analyzing that how T cells are able to taste gluten in celiac diseases. Various types of genome-wide association researches has been conducted for identifying genes encoding in the predisposing factor for autoimmunity. According to the study, T cells that are extracted from the intestinal mucosa of patients are identified through gluten peptides.

Celiac disease is an auto-immune disease in which an immune response to dietary gluten leads to inflammation and subsequent atrophy of small intestinal villi, causing severe bowel discomfort and malabsorption of nutrients. The major instigating factor for the immune response in celiac disease is the activation of gluten-specific CD4+ T cells expressing T cell receptors that recognize gluten peptides presented in the context of HLA-DQ2 and DQ8. Here we provide an in-depth characterization of 28 gluten-specific T cell clones. We assess their transcriptional and epigenetic response to T cell receptor stimulation and link this to genetic factors associated with celiac disease. Gluten-specific T cells have a distinct transcriptional profile that mostly resembles that of Th1 cells but also express cytokines characteristic of other types of T-helper cells. This transcriptional response appears not to be regulated by changes in chromatin state, but rather by early upregulation of transcription factors and non-coding RNAs that likely orchestrate the subsequent activation of genes that play a role in immune pathways. Finally, integration of chromatin and transcription factor binding profiles suggest that genes activated by T cell receptor stimulation of gluten‑specific T cells may be impacted by genetic variation at several genetic loci associated with celiac disease. [ABSTRACT FROM AUTHOR]

In celiac disease (CeD), gluten activates adaptive immune cells that cause damage to the small intestinal mucosa. Histological evaluation of intestinal biopsies allows for grading of disease severity. CeD can effectively be treated with a life‐long gluten‐free diet. Gluten challenge of treated CeD patients is used to confirm diagnosis and to test drug efficacy in clinical trials, but patients respond with different magnitudes to the same gluten challenge. In this study of 19 well‐treated CeD patients, proteome analysis of total tissue or isolated epithelial cell compartment from formalin‐fixed paraffin embedded biopsies collected before and after 14‐day gluten challenge demonstrates that patients with strong mucosal response to challenge have signs of ongoing tissue inflammation already before challenge. This low‐level tissue inflammation at baseline is paralleled by increased gluten specific CD4+ T‐cell frequencies in the gut and presence of a low‐level blood inflammatory profile. Thus, apparently well‐treated CeD is frequently not entirely quiescent, with presence of low‐grade inflammation and antigluten immunity in the gut mucosa. Histology assessment alone appears insufficient to judge full recovery and gut mucosal healing of CeD patients. The findings raise a concern whether a seemingly proper gluten‐free diet is able to curb gut inflammation in all CeD patients. [ABSTRACT FROM AUTHOR]

The highly homologous human leukocyte antigen (HLA)-DQ2 molecules, HLA-DQ2.5 and HLA-DQ2.2, are implicated in the pathogenesis of celiac disease (CeD) by presenting gluten peptides to CD4+ T cells. However, while HLA-DQ2.5 is strongly associated with disease, HLA-DQ2.2 is not, and the molecular basis underpinning this differential disease association is unresolved. We here provide structural evidence for how the single polymorphic residue (HLA-DQ2.5-Tyr22a and HLA-DQ2.2-Phe22a) accounts for HLADQ2.2 additionally requiring gluten epitopes possessing a serine at the P3 position of the peptide. In marked contrast to the biased T cell receptor (TCR) usage associated with HLA-DQ2.5-mediated CeD, we demonstrate with extensive single-cell sequencing that a diverse TCR repertoire enables recognition of the immunodominant HLA-DQ2.2-glut-L1 epitope. The crystal structure of two CeD patient-derived TCR in complex with HLA-DQ2.2 and DQ2.2- glut-L1 (PFSEQEQPV) revealed a docking strategy, and associated interatomic contacts, which was notably distinct from the structures of the TCR:HLA-DQ2.5:gliadin epitope complexes. Accordingly, while the molecular surfaces of the antigen-binding clefts of HLA-DQ2.5 and HLA-DQ2.2 are very similar, differences in the nature of the peptides presented translates to differences in responding T cell repertoires and the nature of engagement of the respective antigen-presenting molecules, which ultimately is associated with differing disease penetrance. [ABSTRACT FROM AUTHOR]

Few therapeutic and diagnostic tools specifically aim at T cells in autoimmune disorders, but are T cells a narrow target in these diseases? Lessons may be learned from celiac disease (CeD), one of the few autoimmune disorders where the T cell driving antigens are known, i.e. dietary gluten proteins. T cell clonotypes specific to gluten are expanded, persist for decades and express a distinct phenotype in CeD patients. Cells with this phenotype are increased also in other autoimmune conditions. Accordingly, disease-specific CD4+ T cells form an immunological scar in CeD and probably other autoimmune disorders. We discuss approaches how such T cells may be targeted for better treatment and diagnosis via their antigen specificity or via their expression of characteristic phenotypic markers. CD4+ T cells specific for gluten antigen in patients with celiac disease have a narrow phenotype and they persist for decades. Gluten-specific CD4+ T cells appear to drive the development of celiac disease, and CD4+ T cells with overlapping phenotypical and functional properties may drive the pathogenic immune responses of other autoimmune diseases. Antigen-specific T cells could be efficient targets for therapy. Several approaches are conceivable. Disease-driving CD4+ T cells can be silenced by mechanisms of immune deviation or elimination, by reactivation induced cell death or by use of antibodies targeting characteristic phenotypic markers, including activation markers. Further, disease-driving CD4+ T cells can be controlled by agonists of checkpoint inhibition or antagonists of checkpoint stimulation as well as by interfering with homing to specific or inflamed tissue. [ABSTRACT FROM AUTHOR]

B cells play important roles in autoimmune diseases through autoantibody production, cytokine secretion, or antigen presentation to T cells. In most cases, the contribution of B cells as antigen-presenting cells is not well understood. We have studied the autoantibody response against the enzyme transglutaminase 2 (TG2) in celiac disease patients by generating recombinant antibodies from single gut plasma cells reactive with discrete antigen domains and by undertaking proteomic analysis of anti-TG2 serum antibodies. The majority of the cells recognized epitopes in the N-terminal domain of TG2. Antibodies recognizing C-terminal epitopes interfered with TG2 cross-linking activity, and B cells specific for C-terminal epitopes were inefficient at taking up TG2-gluten complexes for presentation to gluten-specific T cells. The bias toward N-terminal epitopes hence reflects efficient T-B collaboration. Production of antibodies against N-terminal epitopes coincided with clinical onset of disease, suggesting that TG2-reactive B cells with certain epitope specificities could be the main antigen-presenting cells for pathogenic, gluten-specific T cells. The link between B cell epitopes, antigen presentation, and disease onset provides insight into the pathogenic mechanisms of a T cell-mediated autoimmune condition. [ABSTRACT FROM AUTHOR]