Regulatory mechanism of antigen-stimulated lymphocyte migration in intestinal mucosa

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Lymphocytes from gut associated lymphoid tissue (GALT) continuously recirculate throughout systemic circulation and play an important role for intestinal mucosal defense. In this study, we have established an observatory system of lymphocyte migration in rat Peyer's patches using intravital fluorescence microscopy and investigated the altered migration pattem of stimulated T cells as compared with naive T cells. Con A-stimulation of T cells showed the loss of selective adherent properties in Peyer's patches as shown in naive T cells. On the other hand, the adherence of T cells to hepatic sinusoidal endothelium was significantly increased after Con A activation. The enhanced rolling and adherence of lymphocytes was observed in Peyer's patches and submucosal venules of villi when rats were treated with endotoxin, and these changes were mediated largely by alpha4- integrins.Intestinal inflammation was also induced by an intramural injection of peptidoglycan-polysaccharide (PG-PS) from group A streptococci into rat ileal Peyer's patches. We also demonstrated that alpha4-integrin molecule plays a role in the early stages of PG-PS induced T lymphocyte migration to intestinal villus mucosa and Peyer's patches. By this study, we were able to demonstrate the chatnges in T lymphocyte-endothelial interaction after lymphocyte activation and obtained informations about their regulatory mechanisms.