Essential vitamins for an effective T cell response

Figure 1 Structure of vitamin D and retinoic acid. A: The chemical structure of vitamin D3 and vitamin D2 are indicated by line diagrams; B: The chemical structure of retinoic acid is indicated by line diagrams.

Figure 2 Vitamin D and retinoic acid biosynthesis and activity. A: Vitamin D biosynthetic pathways are indicated, showing critical enzymes in particular tissues. Binding of VDR to DNA with RXR is indicated in a T cell; B: Retinoic acid biosynthetic pathways are indicated. Binding of RAR to DNA with RXR is indicated in an immune cell. RXR: Retinoid X receptor; VDR: Vitamin D receptor; RAR: Retinoic acid receptor; CRBP: Cellular retinol-binding proteins; RDH: Retinol dehydrogenases; VDRE: Vitamin D response element; RARE: Retinoic acid response element; CRABP: Cellular retinoic acid binding proteins.

Figure 3 Effects of vitamin D and retinoic acid on T helper cell differentiation. A: The effects of vitamin D on each of the T helper subsets are indicated, detailing changes in expression of cytokines and transcription factors; B: The effects of retinoic acid on each of the T helper subsets is indicated, detailing changes in expression of cytokines and transcription factors. IL: Interleukin; TGF: Transforming growth factor; Treg: Regulatory T cell.