Lymphocyte Subpopulations in Jejunal and Ileal Peyer's Patches of Calves with Experimental Salmonella dublin Infection

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Abstract
Changes of lymphocyte subpopulations in jejunal and ileal Peyer's patches (JPP and IPP) of six calves inoculated with Salmonella dublin were investigated at 9 hours, 1, 2, 3 and 7 days post inoculation (p.i.) using immunohistochemistry. Reactive areas and area percentages of B-lymphocytes, as well as CD4+, CD8+ and gamma delta T-lymphocytes within the different compartments of PP were estimated using computer-assisted morphometric analysis. A significant, linear decline of the areas of lymphoid follicles and domes in JPP and IPP due to depletion of B-lymphocytes was found. The rate of decline was similar in JPP and IPP, but more severe in lymphoid follicles than in domes. Intraepithelial cells in follicle-associated epithelium changed from predominantly B-lymphocytes in controls to CD8+ T-lymphocytes in inoculated calves and clusters of B-lymphocytes were observed above domes at days 1 and 2 p.i. Areas of CD4+ and CD8+ T-lymphocytes within lymphoid follicles and domes were increased at 3 and 7 days. p.i. resulting in decreased compartmentalization of the normally segregated T- and B-lymphocyte populations. The increase of CD4+ and CD8+ T-lymphocytes was, however, significant in lymphoid follicles in the JPP only. No significant changes in the amount and distribution of gamma delta T-lymphocytes were observed.