12-O-tetradecanoylphorbol-13-acetate (TPA) treatment elevates the natural killer (NK) sensitivity of certain human lymphoid lines

The natural killer (NK) sensitivity of two Epstein-Barr virus (EBV)-carrying Burkitt lymphoma lines (Daudi and Raji) and one EBV-negative acute lymphocytic leukemia-derived T-cell line (Molt-4) increased when they were cultured for 24 hr in the presence of the phorbol ester TPA. In the EBV-carrying lines, this increase occurred independently of the entry of the cells into the viral cycle. 12-O-Tetradecanoylphorbol-13-acetate (TPA)-treated Daudi and Molt-4 cells cross-competed for the effectors in the NK assay as indicated by the cold-target inhibition tests. TPA-treated cells showed an increased binding of human but not of mouse lymphocytes.