In this study, we investigate whether human inflammatory bowel disease (IBD) (ulcerative colitis and Crohn's disease) is associated with altered lymphokine secretion profiles, as recently found in various animal models of chronic intestinal inflammation. In initial studies, we determined the proliferative responses of purified lamina propria (LP) CD4+ T cells from patients with IBD under defined conditions of T cell stimulation. We found that IBD LP CD4+ T cells in comparison with control LP CD4+ T cells have diminished TCR/CD3 pathway proliferative responses, whereas CD2/CD28 accessory pathway proliferative responses are relatively preserved. In further studies centering on lymphokine production, we showed that LP T cells from inflamed Crohn's disease mucosa manifest increased IFN-gamma secretion compared with control LP T cells, particularly when stimulated via the CD2/CD28 pathway. Subsequent ELISPOT analysis indicated that this was due to an increased number of IFN-gamma-secreting CD4+ T cells. In contrast, IL-4 and IL-5 production by Crohn's disease LP T cells was decreased compared with that of control LP T cells. Of interest, IL-2 production by Crohn's disease LP T cells was also reduced, as was IL-2 production by peripheral blood T cells. In parallel studies, LP T cells from inflamed ulcerative colitis mucosa stimulated via either the TCR/CD3/CD28 or CD2/CD28 produced increased amounts of IL-5, again when measured either as secreted IL-5 or by ELISPOT analysis. Such increased IL-5 production was not associated with increased IL-4 secretion and, in contrast to Crohn's disease, ulcerative colitis LP T cell production of IL-2 and IFN-gamma was normal. Taken together, these studies provide strong evidence that the immunopathologic process characteristic of the two major forms of IBD is associated with very different cytokine secretion patterns. These different patterns may determine the type of inflammatory process present.

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