IMMUNOMODULATORY ACTIONS OF 1,25-DIHYDROXYVITAMIN D-3

The sterol, 1,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3), has immunosupp ressive activity. The hormone inhibits the production of lymphokines ( IL-2, IFN-gamma) and monocyte-derived cytokine (IL-12) leading to inhi bition of helper T cell subset type 1 (Th-1). When given in vivo, the hormone prevents the development of spontaneous and induced models of autoimmunity. Analogs of 1,25(OH)(2)D-3, with reduced hypercalcemic ef fects, display an enhanced activity in autoimmunity compared to the st erol and prolong graft survival in experimental transplantation. This paper reviews our understanding of the cellular actions of the hormone and the therapeutic application of 1,25(OH)(2)D-3 and analogs in auto immunity and transplantation.