This project will determine the role of intestinal bacteria products (superantigens) in induction and modulation of mucosal inflammation. The effects of superantigens on the capacity of subpopulations of T-cells to proliferate and secrete cytokines in normal mucosa will be compared to those in patients with inflammatory bowel disease (IBD). Our hypothesis is that in IBD, the mucosal T-cell repertoire is more responsive to bacterial superantigen activation and/or more refractory to down- regulation by molecules such as PGE2 that are increased during gut inflammation. This would lead to exaggerated levels and/or different repertoires of cytokines, thus generating exaggerated responses in the disease state. Recent evidence shows that activated T-cells and their secreted cytokines, e.g., IFN-gamma and TNF-alpha, have a central role in the modulation of epithelial cell integrity and damage in IBD. Studies performed in our laboratory have determined that anti-CD3 and anti-CD2-induced mucosal T-cell activation is capable of triggering the production of these important cytokines, and that mucosal T-cells are predominantly activated through the CD2 molecule. Furthermore, bacterial superantigens have now become recognized as potent initiators and modulators of T-cell activation. The T-cell receptor interacts with bacterial superantigens using a novel mechanism of activation different from antigen presented by antigen presenting cells. At present, very little is known about the interaction of intestinal bacteria and superantigens with mucosal T-cells in IBD. This study proposes to use T-cells isolated from normal as well as disease mucosa (involved and uninvolved mucosa from patients with ulcerative colitis and Crohn's disease), and several defined superantigens to determine the effects of these products on T-cell proliferation, cytokine production and down- regulation. Bacterial superantigens may act as environmental triggers which initiate or perpetuate the inflammatory cascade in the mucosa by activating select groups of T-cells which are crucial to the initiation of the inflammatory process of IBD both in the local tissue as well as at distant sites. This project will: A) Characterize superantigen activation of mucosal T-cells and peripheral blood T-cells, as measured by cell proliferation; B) Characterize superantigen activation of mucosal T-cells and peripheral blood T-cells, as measured by cytokine production and secretion; C) Characterize PGE2 effects of superantigen induction of mucosal T-cell and peripheral blood T-cell proliferation and cytokine secretion; D) Compare inflammatory bowel disease (IBD) mucosal T-cells with normal mucosal T-cells, in terms of the effect of superantigens on proliferation; cytokine secretion; susceptibility to modulation by PGE2. These studies delineate a seminal approach to identify bacterial products and their mechanisms that can initiate and/or propagate IBD. By identification of these agents, it may be possible to avoid or otherwise modify or prevent them from triggering IBD and prevent disease expression.
