Corroborating this migration theory is our data showing discordant IL-17 vs. Th17 levels found early on after immunization (1 week); propionate elevated IL-17 production in the ileum at a time when it reduced Th17 numbers in the MLN, suggesting that there may be propionate-induced retention of Th17 in the ileum prior to the onset of uveitis. The gene discussed is IL17A; the disease is uveitis.