Direct inhibition of murine B lymphocyte differentiation by 12-O-tetradecanoylphorbol-13-acetate

The tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibits the humoral immune response of lymphocytes to antigen. To test the hypothesis that this inhibition is due to a direct effect upon B lymphocytes, splenic lymphocytes or murine B lymphocytes, enriched by 'panning' splenic lymphocytes onto anti-IgM-coated petri dishes, were immunized in vitro with the thymus/accessory cell-independent antigen trinitrophenyl lipopolysaccharide (TNP-LPS) with or without TPA. The number of anti-TNP antibody-forming cells present in both lymphocyte populations after 5 days was almost completely inhibited to the same degree by TPA. These data unambiguously show that TPA can directly inhibit the differentiation of B lymphocytes to antibody-forming cells.