CCR9 and Arthritis: In a collagen-induced arthritis model, inflammation was suppressed in CCR9-deficient mice or using the CCR9 antagonist CCX8037.[14] In contrast, in an antigen-induced arthritis model, CCR9-deficient mice developed arthritis that was not significantly different in severity from wild-type animals.[21] These different results may be due to the different mouse models used, and the exact mechanism needs to be further explored.