CYP27B1 and infection: The discovery of the Vitamin D receptor (VDR) and cytochrome P450 27B1 (CYP27B1) enzyme expression on immune cells has driven exploration into whether the active metabolite of vitamin D, 1,25 dihydroxyvitamin D3 [1,25(OH)2D3] (VitD3), has immunoprotective properties in the context of infection (9–12).