Activation of human T lymphocytes by phorbol-12,13-dibutyrate and ionomycin.
The calcium ionophore ionomycin and the phorbol ester phorbol-12,13-dibutyrate (PDBu) are shown to have a synergistic effect upon interleukin 2 (IL-2) production, interleukin 2 receptor expression, and T-lymphocyte proliferation. The proliferative response was inhibited by addition of a monoclonal antibody directed against the IL-2R (Tac antigen) demonstrating that PDBu and ionomycin induce T-cell growth through an IL-2-dependent autocrine pathway. Sequential stimulation with PDBu and ionomycin failed to induce IL-2 production, IL-2R expression, and consequently proliferation of the T cells, indicating that T-cell activation requires simultaneous activation of protein kinase C (PKC) and elevation of cytosolic calcium. Exposure of T cells to both agents for different times resulted in IL-2 production, IL-2R expression, and proliferation in proportion to the duration of incubation with at least 4 h required for maximal T-cell activation. Further, in the presence of PDBu maximal T-cell activation was found to require stimulation with ionomycin for 4 h, indicating that a sustained increase in free cytoplasmic calcium of several hours' duration is essential for T-cell activation. In contrast T cells incubated with ionomycin were induced to produce IL-2 and express IL-2Rs upon brief exposure to PDBu with a 2-h incubation period being sufficient for maximal T-cell activation. Thus transient activation of PKC seems to be sufficient for activation of the IL-2 gene and IL-2R gene. However, maximal T-cell activation requires activation of PKC for at least 2 h.
Larsen
C S
CS
Department of Medicine and Infectious Diseases, Marselisborg Hospital, Aarhus, Denmark.
D000911:Antibodies, Monoclonal / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D004357:Drug Synergism; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D010835:Phytohemagglutinins / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D015375:Receptors, Interleukin-2 / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D000911:Antibodies, Monoclonal; D010835:Phytohemagglutinins; D015375:Receptors, Interleukin-2; D015240:Phorbol 12,13-Dibutyrate; D015759:Ionomycin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium