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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]

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]

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]

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]

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]

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]

Transglutaminase 2 (TG2) is a ubiquitous crosslinking enzyme present in both intra- and extracellular in many cell types and tissues. TG2 is upregulated upon cellular stress or injury, and extracellular TG2 is implicated in several human diseases, including celiac disease. However, incomplete knowledge about extracellular TG2 biology limits our understanding of how TG2 is involved in disease. Here, we demonstrate that binding of TG2 to the ECM of small intestinal tissue sections is the sum of binding to fibronectin (FN) via its N-terminal domain and binding to an abundant, novel extracellular matrix (ECM) interaction partner via its second C-terminal beta-barrel domain. The latter interaction dominates and gives rise to the characteristic reticular staining pattern of extracellular TG2. Of relevance for celiac disease, we show that self-multimerized TG2 does not efficiently deposit in the intestinal ECM, and TG2 complexes may thus become free-floating antigens in tissues in contrast to monomeric TG2 that would readily become sequestered by the ECM. Upon injection of monoclonal antibody targeting the FN-binding site, we observe antibody deposition on extracellular TG2 in cryosections, suggesting that the FN-binding site of TG2 is exposed in vivo. This would explain how and why celiac autoantibodies recognizing the FN-binding site of TG2 can bind TG2 in vitro, in situ as well as in vivo. [ABSTRACT FROM AUTHOR]

Pathogenic T Cells in Celiac Disease Change Phenotype on Gluten Challenge: Implications for T-Cell-Directed Therapies Grey background indicates time period of gluten ingestion. gl The authors apologize for any inconvenience caused. Median of symptoms expressed in a VAS score (maximal value 100 mm) for the categories Pain, Bloating, Flatulence, Nausea, Satisfaction with defecation and Total complaints and GSRS questionnaire for the categories Pain, Bloating, Constipation, Diarrhea and Satiety in total n = 17 celiac disease patients undergoing a 3-day gluten challenge. [Extracted from the article]

Transglutaminases have been implicated in various human diseases. A prominent example is the involvement of transglutaminase 2 ( TG2) in the gluten-sensitive enteropathy celiac disease, where the enzyme is both the target of autoantibodies and responsible for the generation of immunogenic gluten epitopes. Here, we aimed to characterize the microenvironment of TG2 in the extracellular matrix ( ECM) in order to gain insights into the antigenic structures that are recognized by autoantibodies in celiac disease. A panel of TG2-specific mAbs established from gut plasma cells of celiac disease patients was employed as probes to characterize the interactions between TG2 and ECM constituents. With immunofluorescence staining, microplate protein-binding and surface plasmon resonance assays, we found that the main epitope (epitope 1) recognized by TG2-specific gut plasma cells overlaps with the fibronectin ( FN)-binding site of TG2. Furthermore, we found that the same TG2 amino acids that are involved in binding of epitope 1 mAbs are also important for efficient binding of FN. Notably, epitope 1 mAbs recognize TG2 in tissue sections, suggesting that some TG2 in the extracellular matrix has interaction partners in addition to FN. We demonstrate that collagen VI is a strong candidate, on the basis of its tissue expression pattern and ability to bind TG2. Collagen VI may thus serve as a matrix for deposition of TG2 in a context that can also be recognized by epitope 1-targeting autoantibodies. [ABSTRACT FROM AUTHOR]