Dendritic cell modulation by 1α,25 dihydroxyvitamin D3 and its analogs:: A vitamin D receptor-dependent pathway that promotes a persistent state of immaturity in vitro and in vivo

Dendritic cells (DCs) play a central role in regulating immune activation and responses to self. DC maturation is central to the outcome of antigen presentation to T cells. Maturation of DCs is inhibited by physiological levels of 1 alpha ,25 dihydroxyvitamin D-3 [1 alpha ,25(OH)(2)D-3] and a related analog, 1 alpha ,25(OH)(2)-16-ene-23-yne-26,27-hexafluoro-19-nor-vitamin D-3 (D-3 analog). Conditioning of bone marrow cultures with 10(-10) M D-3 analog resulted in accumulation of immature DCs with reduced IL-12 secretion and without induction of transforming growth factor beta1. These DCs retained an immature phenotype after withdrawal of D-3 analog and exhibited blunted responses to maturing stimuli (CD40 ligation, macrophage products, or lipopolysaccharide). Resistance to maturation depended on the presence of the 1 alpha ,25(OH)(2)D-3 receptor (VDR). In an in vivo model of DC-mediated antigen-specific sensitization, D-3 analog-conditioned DCs failed to sensitize and, instead, promoted prolonged survival of subsequent skin grafts expressing the same antigen, To investigate the physiologic significance of 1 alpha ,25(OH)(2)D-3/VDR-mediated modulation of DC maturity we analyzed DC populations from mice lacking VDR. Compared with wild-type animals, VDR-deficient mice had hypertrophy of subcutaneous lymph nodes and an increase in mature DCs in lymph nodes but not spleen. We conclude that 1 alpha ,25(OH)(2)D-3/VDR mediates physiologically relevant inhibition of DC maturity that is resistant to maturational stimuli and modulates antigen-specific immune responses in vivo.