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. Author manuscript; available in PMC: 2016 May 27.
Published in final edited form as: Adv Pharmacol. 2015 May 27;74:373–412. doi: 10.1016/bs.apha.2015.04.006

Figure 3. Retinoic acid in steady state immune homoestatsis.

Figure 3

A) Throughout the body RA plays an important role in the ratio of Th1:Th2 cells by reducing differentiation of naïve T-cells into IFN-γ producing Th1 cells and promoting differentiation of Th2 cells which secrete IL-4 and IL-5. B) In gut associated lymphoid tissue dendritic cells (DCs) synthesize RA, which acts synergistically with TGF-β to initiate differentiation of Foxp3+ Treg cells and suppress T-cell differentiation into Th17 cells. RA produced by DCs also induces the expression of α4β7 and CCR9 on naïve T-cells to prompt gut homing to the lamina propria over peripheral lymph nodes. Cytokines shown are not a complete list but were chosen based on relevance to the text.