IL-15 mediates TLR2/1L-induced expression of CYP27b1, the VDR and cathelicidin. a, Cell surface expression of IL-15 following activation of monocytes with a TLR2/1L. b and c, Human peripheral monocytes were stimulated in 10% FCS with a TLR2/1L in the presence of medium, an IL-15 blocking Ab, or an isotype control Ab. Levels of CYP27b1 (n = 10) and VDR (n = 5) mRNA were measured after 24 h using qPCR. d, Monocytes were stimulated as above in vitamin D-sufficient serum (100 nM). Levels of cathelicidin (n = 6) mRNA were measured after 24 h using qPCR. Fold activation was calculated as ratio to media control cells (−). Data (b–d) are shown as the average ± SEM. e, Percent inhibition of TLR2/1-induced expression of CYP27b1, VDR, and cathelicidin by the IL-15 mAb. *, p < 0.05, **, p < 0.01.