CXCR4 and rheumatoid arthritis: Chemokine receptors on T cells [CCR2, CCR4, CCR5, CCR6, CCR7, CXCR3, CXCR4, CXCR6, and CX3CR1 (111, 126–129)], B cells [CCR5, CCR6, CCR7, CXCR3, CXCR4, and CXCR5 (130–132)], monocytes [CCR1, CCR2, CCR5, CCR9, CXCR4, and CX3CR1 (33, 100, 133–137)], macrophages [CCR7, CCR9, and CXCR3 (100, 138)], and neutrophils [CCR1, CCR5, CXCR1, and CXCR2 (79, 106, 139)] were more highly expressed in patients with RA than in HD.