CXCL13 and rheumatoid arthritis: In the pathogenesis of human RA, CXC-chemokines promote neutrophils (CXCL1, CXCL2, CXCL5 and CXCL8) (16), the effector T cell (CXCL10) (17) and the B cell (CXCL13) (18), (19) recruitment into the joint.