Peripheral blood mononuclear cells have been shown to express vitamin D receptors. Incubation of macro¬phages with physio¬logical concentration of 1,25 (OH)D [10-9M] results in inhibition of intracellular growth of Mycobacterium tuberculosis. 1,25-dihydroxycholecalciferol, has significant immunomodulatory effects leading to (a) shift in cytokine profile of T-helper (Th1 to Th2) and (b) reduced antigen presentation, reduced production of Th1-promoting cytokines, reduced expression of co-stimulatory molecules in the antigen-presenting cell. In addition, it was demonstrated that the addition of vitamin D3 derivatives inhibits the differentiation of IFN-gamma-producing Th1 cells while it augments the differentiation of IL-4- or IL-10-producing Th2 cells.