CCR9 and rheumatoid arthritis: Similarly, treatment of EAE mice with IL-4 increased retinaldehyde dehydrogenase (RALDH) activity in DCs, which enhanced RA production, induced expression of α4β7 and CCR9 on CD4+ T cells and deviated their migration from the dLNs-CNS route to the mLNs-gut thus improving EAE outcome without overt colitis [130].