Immunoperoxidase localization of large granular lymphocytes in normal tissues and lesions of athymic nude rats.

The immunocytochemical localization of cells reacting with the OX-8 monoclonal antibody was studied in athymic nude rats by the avidin-biotin-peroxidase complex (ABC) immunoperoxidase technique. By a number of criteria, including morphology and tissue distribution of OX-8-positive cells, it is postulated that the majority of lymphocytes reacting with OX-8 antibody in nude rats are LGL. The cell surface of large lymphocytes reacted with the OX-8 antibody in fixed tissue sections. The tissues with the greatest density and percentages of these reactive cells included the paracortex of lymph nodes in association with interdigitating cell (IDC) hyperplasia, bronchial-associated lymphoid tissue (BALT), the medullary cords and sinuses of lymph nodes, and intestinal epithelium. Ultrastructure of the paracortical areas of IDC hyperplasia revealed granular lymphocytes in close association with IDC. Tissues with the fewest positive cells included bone marrow, B cell areas of lymphoid tissues, and parenchymal epithelial organs. In healthy and cachectic nude rats, various incidental and pathologic lesions contained a significant number of OX-8-positive cells. Large numbers of positive lymphocytes were seen in suppurative pneumonic lesions, enteritis, focal ulcerative epithelial lesions, and papovaviral sialoadenitis. The observation of a large number of OX-8-positive lymphocytes in nonlymphoid organs supports the hypothesis that these cells play a major role in the first line of defense against not only tumors but also infectious agents.