1alpha,25-Dihydroxyvitamin D3 modulates CD38 expression on human lymphocytes.

B cells from chronically stimulated tonsils displayed high initial mean CD38 levels that declined during in vitro culture, despite ligation of CD40 and/or the Ag receptor in the presence of IL-4. Exposure to 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) restored the initial CD38 expression on these stimulated cells and up-regulated the Ag on stimulated CD38-/low cells. 1,25(OH)2D3 enhanced CD38 expression by four- to sixfold on CD8- and CD8+ peripheral blood T cells following PHA activation.