CCR9 and rheumatoid arthritis: These results, along with the findings that the percentages of LPAM-1+CCR9+ cells are increased in both the PBMCs of RA patients (Figure 1N) and systemically in arthritic K/BxN and AIA mice (Figures 3A and S3N), prompted us to assess whether inhibiting the recirculation of these cells between the gut and the periphery would reduce the severity of arthritis.