Vitamin D Oily fish, liver, eggs, fortified foods (spreads and some breakfast cereals) Regulates antimicrobial proteins (cathelicidin and β-defensin), modifying intestinal microbiota to a healthier composition and supporting the gut, as well as protecting the lungs against infection; ↑ tight junction protein expression, E-cadherin and connexion 43 in the gut; maintains renal epithelial barrier function; ↑ corneal epithelial barrier function
Vitamin D receptor found in, e.g., monocytes, macrophages, and DCs; ↑ differentiation of monocytes to macrophages; calcitriol ↑ movement and phagocytic ability of macrophages
Regulates antimicrobial protein expression (cathelicidin and defensin), which directly kill pathogens, especially bacteria; ↓ IFN-γ production
↑ The oxidative burst potential of macrophages; increases superoxide synthesis; reduces the expression of pro-inflammatory cytokines and increases the expression of anti-inflammatory cytokines by macrophages
Homing of T cells to the skin; ↓ T-cell proliferation; inhibitory effects mainly in adaptive immunity (e.g., Th1-cell activity); stimulatory effects in innate immunity; ↓ the effector functions of T helper cells and cytotoxic T cells; ↑ the production of Tregs; inhibitory effect on the differentiation and maturation of the antigen-presenting DCs, and helps program DCs for tolerance
↓ Antibody production by B cells
↑ Antigen processing; role in the down-regulation of MHC-II) [64, 71, 79–81, 85, 95, 99, 104–106, 151–153]