Differential distribution of lymphocytes and accessory cells in mouse Peyer's patches

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Abstract
The aim of this immunohistologic study was to determine how lymphocytes and accessory cells associated with antigen processing are distributed in the domes of Peyer's patches. Monoclonal antibodies against mouse B cells (anti‐B220), T cells (anti‐Thy‐1.2), T helper cells (anti‐L3T4), T cytotoxic/suppressor cells (anti‐Lyt‐2), macrophages (anti‐Mac‐1), and Ia+ cells (anti‐I‐Ad) were applied to cryostat sections of mouse Peyer's patches and visualized with peroxidase‐conjugated avidin‐biotin complexes (ABC). The subepithelial dome, the dome epithelium, and the follicle crypt epithelium were each surveyed for cells labeled with these antibodies. Each region had a characteristic and nonrandom distribution of labeled cells. In the subepithelial dome, B cells, T helper cells, macrophages, and Ia + accessory cells formed a cellular meshwork between follicle and the dome epithelium. T cytotoxic/suppressor cells were sparse beneath the epithelium. In the dome epithelium, solitary and paired lymphocytes occurred both above and below the level of epithelial cell nuclei. B cells predominated, and both T helper cells and T cytotoxic/suppressor cells were present. B cells sometimes aggregated in small clusters. Macrophages were rarely observed in the epithelium. The distribution of cells in the dome epithelium was distinctly different from non–Peyer's patch intestine where T cytotoxic/suppressor cells predominated and B cells were few in number. Although lymphocytes were usually absent in crypts outside Peyer's patches, in follicle crypts B cells and T cells were seen but not Ia + accessory cells or macrophages. Most of the T cells in the crypt epithelium were T cytotoxic/suppressor cells. These characteristic distributions in Peyer's patch domes and crypts are consistent with current hypotheses that antigen processing takes place in follicle domes and that specific lymphocytes may participate in fine regulation of stem cell differentiation in follicle crypts.