Table 1.

Local Production and Effects of 1,25D in the Respiratory Tract

Cell type	Conversion of 25D → 1,25D	1.25D Effects	References
Airway Epithelium	Constitutive	Increases CD14 and cathelicidin. Dampens IFN-β and chemokine response during viral infection	Hansdottir et al.
Alveolar Macrophages	Upon activation	Increases the antimicrobial peptide cathelicidin	Liu et al.
Dendritic Cells	Increases with differentiation	Inhibits dendritic cell differentiation, maturation and function, decreases IL-12 and increases IL-10, alters T cell activation	Fritsche et al., Sigmundsdottir et al., Piemonti et al., Penna et al
T lymphocytes	At least when activated	Inhibits proliferation, modulates cytokine production - inhibits Th1 and Th17 cytokines but induces Tregs	Sigmundsdottir et al., Lemire et al., Daniel et al., Mora et al., Penna et al.
B lymphocytes	Unclear	Inhibits proliferation of activated B cells and generation of plasma cells	Chen et al.