CAMP and bacterial infectious disease: Moreover, genes commonly used as in vitro markers, are either not expressed like in the case of CAMP (cathelicidin antimicrobial peptide) (52) due to the absence of bacterial infection in the study participant, or not significantly induced, as with CYP24A1 (cytochrome P450 family 24 subfamily A member 1) (10), which may reflect its higher basal expression in vivo and the comparatively modest increase in 1,25(OH)2D3 levels.