In situ demonstration of T lymphocyte subsets in granulomatous inflammation: leprosy, rhinoscleroma and sarcoidosis.

T lymphocyte subpopulations in frozen tissue sections of four granulomatous conditions (five patients with tuberculoid leprosy, five with lepromatous leprosy, seven with sarcoidosis and four with rhinoscleroma) were studied using monoclonal antibodies and a modified immunoperoxidase technique. Two immunohistological patterns were observed. In tuberculoid leprosy and sarcoidosis, lymphocytes expressing the helper/inducer phenotype were present within the aggregates of mononuclear phagocytes (epithelioid cells); however, cells with the suppressor/cytotoxic phenotype were predominantly in the lymphocytic mantle surrounding each granuloma. In lepromatous leprosy and rhinoscleroma the helper/inducer T cells and suppressor/cytotoxic T cells were both diffusely distributed among the mononuclear phagocytes (histiocytes) without any discernible mantle. The segregation of the helper/inducer and suppressor/cytotoxic phenotypic subsets was associated with an epithelioid cell differentiation of mononuclear phagocytic cells, bacterial elimination and a delayed type hypersensitivity response. The intimate admixture of helper/inducer and suppressor/cytotoxic subsets was associated with undifferentiated mononuclear phagocytes, bacterial proliferation and the absence of a delayed type hypersensitivity response. Thus the different distributions of T cell subpopulations in granulomas may be associated with differences in the host's immune response in several forms of granulomatous reactions.