ABSTRACT
The active form of vitamin D, 1,25 dihydroxy-vitamin D (1,25(OH)2D), binds to the vitamin D receptor (VDR), which is expressed in most cells. 1,25(OH)2D functions as a steroid hormone, usually by heterodimerization with the retinoid X receptor, binding to vitamin-D response elements (VDRE) located in promoter regions. It induces the expression of target genes involved in many cellular responses, including the immune responses.
