Effects of vitamin D on immune cells: (a) Macrophages and dendritic cells; (b) T lymphocytes, regulatory T (Treg) lymphocytes, B lymphocytes. CCR6, CCR10, chemokine receptor; CLA, conjugated linoleic acid; CDK-4,-6, cyclin-dependent kinase; ERN1, endoplasmic reticulum to nucleus signalling-1; FOXP3, forkhead box P-3; GM-CSF, granulocyte–macrophage colony-stimulating factor; DCs, dendritic cells; CYP24-SV, 24-hydroxylase splice variant form; CYP27B1, 25-hydroxyvitamin D-1 α-hydroxylase; Ig, immunoglobulin; iNOS, inducible nitric oxide synthases; IFN-γ, interferon-γ; IL-1, interleukin-1; LPS, lipopolysaccaride; MHC-2, major histocompatibility complex-2; MMP-7, matrix metalloproteinase-7; M. tb, Mycobacterium tuberculosis; NF-κB, nuclear factor-κB; NOD2/CARD15/IBD1, nucleotide-binding oligomerization domain containing 2/Caspase activation and recruitment domains/inflammatory bowel disease 1; Tregs, regulatory T cells; PAMPs, pathogen-associated molecular patterns; PBMC, peripheral blood mononuclear; PLC-γ1, phospholipase C-γ1; PGE2, prostaglandin E2; TCR, T-cell receptor; TLR-2, toll-like receptor-2; TGF-β1, transforming growth factor-β1; TNF-α, tumour necrosis-α; VDR, 1,25(OH)2D3 receptor; Th-1, T helper type 1; XBP1, X-box binding protein-1.