Effect of purified human interferon-alpha on the expression of differentiation antigens and mitogen reactivity of cultured human thymic cells.

Human thymic cells were cultured in vitro either alone or with the addition of a highly purified preparation of human interferon-alpha. Immunofluorescence techniques using a series of monoclonal antibodies showed that 2-day cultured thymocytes express a more mature phenotype (low HTA 1, high T3 and HLA-A,B,C) than normal, uncultured thymocytes. Interferon addition to the cultures results in a strong increment in the number of HLA+ cells and in the total amount of HLA expressed by the cultured cells. Experiments with purified cell populations showed that the cortical, immature, thymocyte was the target cell for interferon action. Phytohemagglutinin responses--but not interleukin 2 responses--were diminished after pretreatment of thymic cells with interferon. We suggest that interferon may favor a pathway of intrathymic differentiation phenotypically characterized by a high content of Class I HLA antigens.