Enhanced lymphocyte interaction in postcapillary venules of Peyer's patches during fat absorption in rats

Background and Aims: Although dietary fat is known to modulate immune functions, there is a paucity of data concerning the effects of fat absorption on migration of lymphocytes in intestinal lymphoid tissue. The objective of this study was to assess the influence of fat absorption on T- lymphocyte migration in Peyer's patches. Methods: T lymphocytes collected from rat intestinal lymph were labeled with carboxyfluomscein diacetate succinimidyl ester and injected into the jugular vein of recipient rats. Olive oil or octanoic acid was placed into the duodenum, and Peyer's patch microcirculation was observed by intravital fluorescence microscopy. Results: Rolling and adherence of lymphocytes in peetcapillary venules were noted in both fasted and fed rats. However, lymphocyte adherence was significantly greater in olive oil-fed rats than in fasted rats. Olive oil also significantly increased the transendothelial migration of T lymphocytes. Octanoic acid stimulated lymphocyte rolling but did not affect lymphocyte adherence. Olive oil enhanced the expression of both α₄-integrin and L- selectin on lymphocytes, whereas octanoic acid only increased the expression of L-selectin. Conclusions: Lymphocyte rolling and adherence are enhanced by olive oil feeding, possibly through an interaction between activated adhesion molecules on lymphocytes and counter-receptors on endothelial cells.