Endotoxin stimulates lymphocyte-endothelial interactions in rat intestinal Peyer's patches and villus mucosa

Although lymphocyte-endothelial cell interactions represent a key step in controlling the recruitment of lymphocytes into gut-associated tissues, its dynamic process in microvessels of lymphold (peyer's patches and nonlymphoid (villus) regions of the small bowel remains poorly understood. We monitored the migration of fluorescence-labeled T lymphocytes into normal and lipopolysaccharide (lps)-inflamed rat intestinal microvessels using intravital microscopy. In Peyer's patches, T lymphocytes selectively adhered to postcapillary venules, although such selectivity was not observed in submucosal venules of villi. T lymphocytes exhibited rolling behavior followed by firm adhesion in microvessels of both the Peyer's patches and the villi, with both types of adhesive interaction being mediated by α₄- integrins. The enhanced rolling and adherence of lymphocytes observed in Peyer's patches and submucosal venules of villi of Lps-treated rats were preceded by a reduction in shear rate and were mediaterl largely by α₄- integrins and partly by β₂-integrins. In capillaries of intestinal mucosa, lymphocyte adherence occurred without rolling and was independent of α₄- integrins. Lps also significantly increased adherence of lymphocytes to villus capillaries, which was not mediated by either α₄- or β₂-integrin. These observations demonstrate significant heterogeneity of lymphocyte- endothelial cell interactions within different regions of the intestinal mucosa.