Distribution of lymphocyte subsets in the small intestine lymphoid tissue of 1-month-old lambs

Distribution of lymphocyte subpopulations along the small intestine lymphoi d tissue has been examined in 1-month-old lambs using flow cytometric and i mmunohistochemical techniques. Monoclonal antibodies against CD4, CD8, gamm a delta, CD45R and B receptors have been employed in samples from continuou s ileal Peyer's patch (IPP), discrete jejunal Peyer's patches (JPP), ileoca ecal valve lymphoid tissue (ICVPP), mesenteric lymph node (MLN) and intra-e pithelial (IEL) and lamina propria (LPL) lymphocytes. Histological studies were also done. Differences in the lymphocyte distribution have been observ ed between some of the regions examined, especially between IPP and JPP for most of the markers. A remarkable feature was the existence of morphologic al and lymphocyte distribution differences between ICVPP and IPP, locations that had been traditionally considered as similar. The antibody against CD 45R receptor used in this study, that was supposed to mark B cells and some T cells, detected cell populations located in the dome of the follicles in all the samples, whereas the centre was negative. Lymphocytes positive to the B marker employed were located mainly in the centre, suggesting that bo th antibodies would mark B cells in different maturation status.