Influence of PMA on T-lymphocyte responses to mitogenic lymphokines.

Phorbol myristate acetate (PMA), a reagent frequently used in vitro to bypass macrophage function and to elicit cytokines, has a variety of effects on the behavior of T lymphocytes in tissue culture. For example, PMA in concentrations greater than 10(-10)M is highly comitogenic with phytohemagglutinin (PHA) for C3H/HeJ thymocytes, and significantly potentiates lymphokine-induced proliferative responses of long-term MLC cells, cloned cytolytic T cells, and interleukin-2 (IL-2)-dependent T-cell lines. Since these activated T-lymphocyte populations are used to detect IL-2, PMA can interfere with accurate assessment of IL-2 concentration by quantitative bioassay. Further, if greater than 10(-10) M PMA remains as a contaminant in PMA-induced lymphokine preparations, it can mediate lymphokine-like biologic activity, and, therefore, obscure interpretation of experiments involving lymphocyte-lymphokine interactions.