The ligand chemokines, CCL3, CCL4 and CCL5 for CCR5, CCL20 for CCR6, CCL19 and CCL21 for CCR7, CXCL9, CXCL10 and CXCL11 for CXCR3, CXCL12 for CXCR4, and CXCL13 for CXCR5 has been reported to be expressed in the RA synovium [22-29]. The gene discussed is CXCR4; the disease is rheumatoid arthritis.