LYMPHOCYTE COMPARTMENTS IN ANTIGEN-SAMPLING REGIONS OF RABBIT MUCOSALLYMPHOID ORGANS

Uptake and delivery of antigens to immunocompetent cells in the gut ar e critical factors for the development of oral vaccines. Particulate a ntigens are transported within minutes by M cells to intraepithelial l ymphocytes and into the follicle dome. The dome contains B cells, CD4 T cells, and macrophages, indicating that the cells involved in antig en presentation are located below the dome's epithelium. The high numb er of M cells in rabbits and the development of monoclonal antibodies against rabbit lymphocytes have enabled the detailed study of lymphocy tes associated with M cells. The follicle epithelium of rabbit Peyer's patches contains B cells and a population of CD4-/CD8-, major histoco mpatibility complex class II+ mononuclear cells of unknown function. T hese cells are phenotypically distinct from T cells in follicle domes, in T cell-dependent areas, in villus epithelium, or in villus lamina propria. In addition, lymphocytes in M-cell pockets express an activat ion antigen (3B6) not found on CD4+ or CD8+ cells in T cell-dependent areas. These results indicate that M-cell pocket lymphocytes in follic le epithelium form a phenotypically distinct compartment situated at t he interface between M-cell-driven antigen uptake and the mucosal immu ne system.