The coming of age of 1,25-dihydroxyvitamin D3 analogs as immunomodulatory agents

The active form of vitamin D, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], is a secosteroid hormone that regulates calcium and bone metabolism, controls cell proliferation and differentiation, and exerts immunoregulatory activities. This range of functions has been exploited clinically to treat a variety of conditions, from secondary hyperparathyroidism to osteoporosis, to autoimmune diseases such as psoriasis. Recent advances in understanding 1,25(OH)2D3 functions and novel insights into the mechanisms of its immunomodulatory properties suggest a wider applicability of this hormone in the treatment of autoimmune diseases and allograft rejection.