We previously observed that mature osteoclasts highly expressed C-C chemokine receptor type 5 (CCR5) and that CCR5 and C-C motif chemokine ligand 5 (CCL5), a major ligand for CCR5, were involved in bone-destructive diseases, such as osteoporosis and rheumatoid arthritis [20]. The gene discussed is CCL5; the disease is rheumatoid arthritis.