PTPRC and arthritic joint disease: In agreement with patient data showing higher LPAM-1+CCR9+ expression by RA PBMCs compared to healthy individuals (Figure 1N), we observed significant increases in the frequency of LPAM-1+CCR9+CD45+ cells in the spleens, Peyer’s patches (PPs), mesenteric lymph nodes (mLNs), and paw-draining axillary lymph nodes (ALNs) in arthritic K/BxN mice compared to CTRL mice (naive non-obese diabetic [NOD] mice), suggesting that increased cellular circulation to the gut is a feature of arthritis (Figure 3A).