title: 1,25-Dihydroxyvitamin D3 as a natural regulator of human immune functions.
abstract: 1,25-dihydroxyvitamin D3 (1,25-D3) modulates lymphocyte and macrophage functions in vitro. These effects are exerted through production of 1,25-D3 by antigen-presenting monocytes/macrophages (MO) and binding to vitamin D receptors expressed in MO and in activated, but not in resting T-lymphocytes. 1,25-D3 inhibits production of MO-derived cytokines such as interleukin-1 alpha, interleukin-6, and tumor necrosis factor alpha at the post-transcriptional level, most likely by reducing the half-life of specific mRNAs. The proliferation of T-cells and their release of cytokines such as IL-2 and interferon gamma are also suppressed by 1,25-D3, partly as a result of the reduced production of T-cell-activating cytokines (interleukin-1 alpha, tumor necrosis factor alpha), but also because of a direct effect on the T-cells. Although 1,25-D3 has no apparent effect on B-lymphocytes, the T-cell suppression indirectly inhibits antibody production by B-cells. The CD45R0+ subset of T-helper cells is relatively more sensitive than the CD45RA+ subset to the inhibitory effects of 1,25-D3. The CD45R0+ subset plays a key role in immune activation and in the pathogenesis of many autoimmune disease. 1,25-D3 acts as an important local regulator of T-cell functions and thus modulates several immunological effector functions. The actions of 1,25-D3 are distinct from those of commonly used immunosuppressants, and vitamin D3 analogs are therefore potentially useful as alternatives to conventional immunosuppressive therapies.
authors.affiliation: Laboratory of Medical Immunology, RHIMA Center, National University Hospital, Copenhagen, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Müller
authors.forename: K
authors.initials: K
authors.lastname: Bendtzen
mesh_terms: D002117:Calcitriol / Q000494:pharmacology*; D006801:Humans; D007109:Immunity / Q000187:drug effects*; D007249:Inflammation / Q000188:drug therapy; D008214:Lymphocytes / Q000187:drug effects; D009000:Monocytes / Q000187:drug effects
chemical_list: D002117:Calcitriol