The intestinal and rectal epithelial lymphocyte in AIDS. An electron-microscopic study

Injury to the gastrointestinal tract may be mediated in part by the intraepithelial lymphocyte. In this study, we utilized electron microscopy to define the morphological appearance of 86 intestinal and 55 rectal intraepithelial lymphocytes observed in 11 patients with acquired immunodeficiency syndrome (AIDS), and one patient with AIDS-related lymphadenopathy syndrome. The data obtained from intraepithelial lymphocytes of AIDS are compared to those from 106 normal intestinal epithelial lymphocytes and 52 untreated celiac sprue epithelial lymphocytes. The AIDS epithelial lymphocyte possesses more organelles and appears "activated." Eighty-four percent of AIDS epithelial lymphocytes and 44% of normal epithelial lymphocytes possess lysosomal granules. There are 3.3 lysosomal granules/AIDS epithelial lymphocyte and 1.0 lysosomal granule/normal epithelial lymphocyte. Lymphocytes in AIDS usually possess multiple surface projections, which indent and make point contact with adjacent epithelial cells. Thirty-four percent of AIDS epithelial lymphocytes, 23% of sprue epithelial lymphocytes, and 2% of normal epithelial lymphocytes appear "activated." Lymphocytes in AIDS are "activated" in both the presence and absence of gastrointestinal pathogens. Epithelial lymphocytes are increased in intestinal, but not in rectal, AIDS tissue. Mucosal injury, including single cell necrosis, is minimal in the AIDS tissue. We speculate that the "activated" epithelial lymphocyte in AIDS, often possessing large lysosomes, could function as a cytotoxic effector in the development of gastrointestinal immune injury reported to be present in some patients with AIDS.