Identification by monoclonal antibodies of T-cell subpopulations activated by 12-O-tetradecanoylphorbol-13-acetate (TPA).

Two major T-cell subpopulations obtained from human peripheral blood were studied their capacity to be activated by the tumor promoting agent, 12-O-tetradecanoylphorbol-13-acetate (TPA). The subpopulations were identified and separated from each other by their reactivity either to the monoclonal antibody, OKT4 or OKT8, followed by complement-dependent lysis. The fraction enriched in T8+ cells showed approximately a 1.2-2.0-fold greater proliferative response to TPA (20 ng/ml) than did the T4+ cell subset. Optimal activation required the presence of monocytes. Comparison of the mitotic activity showed that the sum of each T-cell subset was less than a mixture of the two. This indicates either a unilateral or cooperative interaction of mitogenesis in the presence of TPA.