Lymphocyte subpopulations in jejunal and ileal Peyer's patches of calves with experimental Salmonella dublin infection.

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.