VDR and bacterial infectious disease: Recently, the microbial-activated toll-like receptors have been shown to upregulate the expression of vitamin D receptors (VDRs) and CYP27b1-hydroxylase in human macrophages.(43) The human cathelicidin antimicrobial peptide gene is a direct transcriptional target of VDR-1,25(OH)2D interaction in those cells.(43,44) Therefore, an insufficient 25(OH)D level a may lso result in prolongation of bacterial infection of the mouth.