Abstract
Interferon‐γ (IFN‐γ) induces the expression of MHC class II antigens on non‐lymphoid cells. In this study we investigated the effect of 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3), the most active metabolite of vitamin D3, on the IFN‐γ‐induced expression of MHCclass II antigens on HEp‐2 cells. We found that 1,25(OH)2D3 enhanced the IFN‐γ‐induced expression of HLA‐DR on these cells. Differential effects on the MHC class II antigens HLA‐DR, ‐DQ and ‐DP were also observed.