Characterizing circulating and visceral T cells specific for the autoantigen integrin αvβ6 in ulcerative colitis

PROJECT SUMMARY/ABSTRACT The integrin heterodimer αvβ6 expressed on intestinal epithelial cells has recently been discovered as the target of autoantibodies uniquely found in nearly every patient with ulcerative colitis (UC), even years before disease onset. We propose to find and characterize the T cells ultimately responsible for letting B cells make these antibodies, and thus reveal a novel insight into how immune self-tolerance to a mucosal autoantigen is lost in UC, or conversely maintained in people without UC. To this end, we will adapt the Activation Induced Marker (AIM) assay that we have used extensively in the study of type 1 diabetes to now evaluate UC. This will allow us for the first time to employ this assay on cells from the mesenteric lymph nodes of humans, where much of the T cell-B cell interactions necessary for gut-centric antibody production occur, and leverage data thus generated into an analysis of the colonic mucosa itself. We are able to do this because we uniquely have a bank of cryopreserved live MLN and colon samples from the surgical resections of dozens of people with UC and Crohn's disease, in addition to cryopreserved live blood cells and serum from hundreds of other UC patients and healthy controls. The AIM assay is designed to independently evaluate pro-inflammatory and regulatory T cells. In addition to finding and immunophenotyping autoantigen-specific T cells by flow cytometry, the AIM assay will allow us to isolate these cells for single-cell analyses of their gene expression profiles and unique T cell receptor sequences. These in turn serve as a unique identifier with which to track autoantigen- specific T cells throughout the body, including in the colon, where autoreactive T cells may play a direct role in promoting or suppressing pathology.