CCR9 and rheumatoid arthritis: We show that RA patients have increased serum levels of lipopolysaccharide (LPS), LPS binding protein (LBP), and intestinal fatty acid binding protein (I-FABP), markers of intestinal damage and permeability, and a systemic rise in leukocytes expressing gut-homing markers chemokine receptor 9 (CCR9) and lymphocyte Peyer's patch adhesion molecule 1 (LPAM-1) compared to healthy individuals.