title: Induction of human B cell proliferation and differentiation by the combination of phorbol ester and ionomycin.
abstract: Phorbol esters and Ca2+ ionophores are known to mimic intracellular messengers involved in cell activation. We studied the effects of 12-O-tetradecanoylphorbol 13-acetate (TPA) and ionomycin on tonsil and peripheral blood-derived B lymphocytes. We show that TPA and ionomycin are co-mitogenic and induce B lymphocyte differentiation. Although TPA in high concentrations is mitogenic to B lymphocytes by itself, submitogenic concentrations of TPA in combination with ionomycin trigger 50% of B lymphocytes to synthesize DNA. Stimulation of B lymphocytes with TPA plus ionomycin resulted in increased magnitude and a shift in the kinetics of c-fos and c-myc expression compared with either agent used alone. Activation markers such as the transferrin and interleukin 2 (IL2) receptors were markedly increased after 24 h incubation with TPA and ionomycin. In parallel to the rapid proliferative burst, we observed evidence for B lymphocyte differentiation with an increase in the number of cells expressing cytoplasmic immunoglobulin (Ig) and the disappearance of the B1 surface marker. Since the cells remained surface Ig+ and secreted only small quantities of Ig, our results suggest that the combination of TPA and ionomycin is a potent inducer of B cell proliferation and early differentiation; terminal differentiation to an Ig-secreting state, however, is not achieved.
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology; D002453:Cell Cycle; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004357:Drug Synergism; D004987:Ethers / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D015759:Ionomycin; D008213:Lymphocyte Activation / Q000187:drug effects*; D014066:Palatine Tonsil / Q000166:cytology; D011519:Proto-Oncogenes; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D000954:Antigens, Surface; D004987:Ethers; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate