Intravital demonstration of sequential migration process of lymphocyte subpopulations in rat peyer's patches

Background & Aims: Although recirculation of lymphocytes through Peyer's patches is important for specific immune defense, the intraorgan migration of lymphocyte subpopulations has not been clearly understood. The aim of this study was to compare the spatial distributions of labeled lymphocytes among various subpopulations in rat Peyer's patches. Methods: Lymphocytes collected from intestinal lymph were separated into CD4⁺, CD8⁺, and T and B cells, labeled with a fluorochrome carboxyfluorescein diacetate succinimidyl ester, and injected into the jugular vein. Peyer's patches of recipient rats were observed by intravital fluorescence microscopy. Results: No significant difference was found in the percentage of lymphocytes in transit or in the rolling velocity among different subpopulations. Lymphocytes sticking to the venules increased in number at 10-20 minutes, with preferential adherence of CD4⁺ cells to venules of 25-50 μm and preferential adherence of B cells to the venules of a wider size range. After 30 minutes, extravasated lymphocytes moved into the interstitium. B cells migrated from venules more quickly than CD4⁺ cells. CD8⁺ cells showed an intermediate pattern between CD4⁺ and B cells in sticking and migratory behaviors. Subsequently, CD4⁺ and CD8 cells preferentially appeared in parafollicular microlymphatics. Conclusions: Significant differences were observed among lymphocyte subpopulations in terms of spatial distribution of lymphocytes sticking to venules, migration into the interstitium, and their lymphatic transport.