title: Inhibition of T lymphocyte mitogenesis by 1,25-dihydroxyvitamin D3 (calcitriol).
abstract: Recent studies have suggested that vitamin D may have other important biologic activities in addition to its well-characterized role in the maintenance of calcium homeostasis. Discovery of cytosolic receptors for vitamin D in human peripheral blood monocytes and lectin-stimulated lymphocytes prompted us to study the effects of 1,25-dihydroxyvitamin D3 (calcitriol), the most biologically active metabolite of vitamin D, upon phytohemagglutinin (PHA)-induced lymphocyte blast transformation. We have found that calcitriol is a potent inhibitor of PHA-induced lymphocyte proliferation, achieving 70% inhibition of tritiated thymidine incorporation after 72 h in culture. Furthermore, calcitriol suppressed interleukin-2 (IL-2) production by PHA-stimulated peripheral blood mononuclear cells in a concentration-dependent fashion. Lastly, the suppressive effect of calcitriol on cellular proliferation was partially reversed by the addition of saturating amounts of purified IL-2. We conclude that calcitriol is a potent inhibitor of PHA-induced lymphocyte blast transformation and that this effect is mediated, in part, through suppression of IL-2 production. Thus, calcitriol appears to possess immunoregulatory properties that have been unappreciated heretofore.
mesh_terms: D002112:Calcifediol / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007376:Interleukin-2 / Q000096:biosynthesis; D007700:Kinetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D010835:Phytohemagglutinins / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D007166:Immunosuppressive Agents; D007376:Interleukin-2; D010835:Phytohemagglutinins; D002117:Calcitriol; D002112:Calcifediol