We also observed the lower proportion of CD4+FOXP3+ Tregs expressing CXCR4 in the BM and blood from RA patients in comparison with OA patients (Figure 3c,d), which may be at least partially responsible for their reduced trafficking to the BM and for the presence of decreased proportion of Tregs in the BM of RA patients. Here, CXCR4 is linked to rheumatoid arthritis.