Phenotypic characterization of human T lymphocyte populations producing macrophage-activating factor (MAF) lymphokines.

Human T lymphocytes, which are known to produce lymphokines that can activate monocytes and macrophages, can be subdivided into two functionally relevant subsets, as indicated by the expression of the T4 and T8 antigens. To determine whether one or both of these T cell subsets is capable of generating macrophage activating factor(s) (MAF) after stimulation with lectin, soluble antigen, or cell surface alloantigen, highly purified populations of T4 or T8 cells were cultured in medium containing PHA, tetanus toxoid-soluble antigen, or allogeneic B lymphoblastoid cells. The resultant culture supernatants were tested for the presence of MAF activity, as manifested by the activation of human peripheral blood monocytes to perform enhanced cytotoxicity and cytostasis against a murine tumor cell line, or to perform antibody-dependent cytotoxicity against anti-RhD-coated human erythrocytes. Both isolated T4 or T8 cells were able to produce MAF activity after stimulation with either PHA or alloantigens, but only the T4 subset generated MAF in response to stimulation with tetanus toxoid. These results coincide with the proliferative capacity of the isolated T subsets to respond to the same stimulators, and demonstrate that the ability to generate MAF lymphokines is not subset restricted.