Distribution of lymphocyte subsets in the large intestinal lymphoid follicles of lambs.

The phenotypes of lymphocytes in the large intestinal patches (LIP) of lambs were examined by flow cytometry and immunohistology, using a panel of monoclonal antibodies (mAb), and compared to those found in the jejunal (JPP) and ileal Peyer's patches (IPP). T-cell markers were detected on 25% of the LIP and JPP lymphocytes by cytofluorometry, and nearly all T cells expressed the CD4 molecule. In contrast, T cells were scarce in the IPP (less than 1%). The B-cell marker p220 was expressed by 74% of the LIP lymphocytes, whereas surface immunoglobulin-positive cells comprised 50-60% of the lymphocyte population. The adhesion molecule CD2 was expressed by a larger proportion of cells from the LIP and JPP than from the IPP, whereas the adhesion molecule CD44 was detected on more IPP lymphocytes. Major histocompatibility complex (MHC) class I antigens were expressed by nearly all lymphocytes from the LIP, JPP and IPP. The LIP contained 70-80% cells with MHC class II expression, whereas the majority of IPP cells (greater than 95%) were MHC class II positive. Immunohistology showed many CD4+ T lymphocytes in the follicles of the LIP and JPP, but none in the IPP follicles. CD8+ lymphocytes were found in the interfollicular areas and were absent from the follicles. The interfollicular areas of the rectal patch contained about 15% tau delta T cells. In contrast, the JPP, IPP and the colon patch at the beginning of spiral colon contained less than 3% tau delta T cells.