1 alpha,25-Dihydroxyvitamin D3 inhibits proliferative response of T- and B-lymphocytes in a serum-free culture

The contribution of 1 alpha,25-dihydroxyvitamin D3 to the proliferative response of human B- and T-lymphocytes was examined in a serum-free culture, in which B-cells were stimulated with Staphylococcus aureus Cowan I, and T-cells with phytohemagglutinin, respectively. 1 alpha, 25-dihydroxyvitamin D3 inhibited mitogen-induced B-cell proliferation at a dose of 10(-7) M (P less than 0.01). T-cell proliferation was inhibited at the lower dose range between 10(-9) M and 10(-7) M. Thus, although 1 alpha, 25-dihydroxyvitamin D3 acts directly on B-cells, it appears that, under physiological circumstance, 1 alpha, 25-dihydroxyvitamin D3 regulates human B-cell growth indirectly through the effect on T-cells.