Ulcerative colitis and Crohn's disease, known as inflammatory bowel disease, are complex, multi-faceted, poorly understood chronic inflammatory diseases of the intestine associated with and probably due to hyperimmune reaction to as yet unknown antigens. Decades of research has not revealed the etiology or clarified the pathogenesis. Workshops held in 1989 identified selected areas of importance for future research. Among these areas felt to be important and addressed in this proposal were a better understanding of the initiating antigens and immunoregulatory mechanisms and the development of new animal models, especially the mouse. We have developed two new models of colitis in the mouse, each involving T cell reactivity against autoantigens. One is based on colon sensitization to the contact allergen TNBS, the other on cyclosporine A interference with thymic deletion of autoreactive T cells following irradiation and bone marrow reconstitution. T cells have been found to be the major initiator of disease in several other mouse models of chronic inflammatory autoimmune disease and may well play a similar role in man. T cells infiltrate the lesions of chronic colitis in large numbers and are thought to play an important role but nothing is known about the antigens they recognize, the assortment of T cell receptors (TCR) used, or their exact role in disease. We postulate that T cells reactive to colon-specific autoantigens play a critical initiating role in murine colitis which may subsequently result in a broad secondary T cell response to antigens present in the colon lumen. This project will focus particularly on the identification of colon autoantigens important in murine colitis and the assortment of T cell receptors used to recognize these antigens. We will expand T cell lines from the colitic lesions and determine their antigen specificity for colon autoantigens using the T cell Western immunoblotting technique. We will determine whether there are a limited number of dominant colon autoantigens for T cells, identify their tissue localization, and determine whether antigens recognized by T cells are the same as or different from those recognized by B cells. Secondly, we will determine the TCR V gene families represented during active colitis and compare these to those used by T cell clones specific for colon autoantigens using immunohistochemistry and flow cytometry in concert with TCR-specific monoclonal antibodies. Third, we will determine whether the mechanism of resistance to the induction of TNBS colitis in certain inbred strains is due to a lack of T cells able to respond to the relevant antigens, a lack of expression of important colon antigens in the resistant strains or a difference in the type of T cells stimulated. Lastly, we will establish the role that colon-specific T cells play in mediating chronic colitis by determining whether colitis can be transferred or enhanced solely by the transfer of T cell clones to adoptive hosts. These studies will lay important groundwork for the conduct of similar investigations in human colitis.
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