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. Author manuscript; available in PMC: 2011 Jun 10.
Published in final edited form as: Mol Cell Endocrinol. 2010 Feb 13;321(2):103–111. doi: 10.1016/j.mce.2010.02.013

Figure 4. Intracrine and paracrine mechanisms involved in mediating the effects of vitamin D on antigen presentation by dendritic cells.

Figure 4

Differentiation of monocytes to immature (iDCs) and mature dendritic cells (mDCs) is associated with the induction of 1α-hydroxylase (CYP27B1) and suppression of vitamin D receptor (VDR) expression. In this way, local conversion of 25-hydroxyvitamin D (25OHD) to 1,25-dihydroxyvitamin D (1,25(OH)2D) can impact on DC function in several ways. A. synthesis of 1,25(OH)2D by mDCs activates VDR signaling in an intracrine fashion despite low numbers of VDR, suppressing DC function and antigen presentation to adjacent niave T-cells (Th0). B. synthesis of 1,25(OH)2D by mDCs activates VDR signaling in an paracrine fashion, suppressing the maturation of adjacent iDCs and thereby promoting tolerogenic T-cell responses. C. synthesis of 1,25(OH)2D by mDCs acts in a paracrine fashion on VDR-expressing T-cells, promoting the generation of immunosuppressive regulatory T-cells (Treg) from Th0 cells.