The tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) induces the production of lymphocyte-activating factors (LAP) in human lymphocyte cultures.

The tumour promoting phorbol ester TPA induces the production of lymphocyte-activating factors (LAF) by human peripheral blood lymphocytes. The noncocarcinogenic and nonmitogenic agent phorbol lacks LAF-inducing properties. Production of LAF by TPA-stimulated lymphocytes occurs independent of the presence of macrophages in cultures and shows a correlation to the dose of TPA used for lymphocyte activation. The possible implications of these observations for the in vitro interaction of phorbol esters and cells of the haemopoietic system are discussed.