CXCR4 and rheumatoid arthritis: When we examined the differential expression of CXCR5, CCR6 and CXCR4 on the cell surface and total expression on B cells from the PB and SF of RA patients, we observed that CXCR5 and CCR6 in SF B cells had undergone an internalization process, whereas CXCR4 had not.