Our disclosure of the activity of the CXCL12/HMGB1 heterocomplex in Rheumatoid Arthritis (8), and the fact that it induces a different conformational change in CXCR4 dimers compared to stimulation with CXCL12 alone (6), prompted us to further investigate the downstream signaling events elicited by CXCR4 triggering. This evidence concerns the gene CXCR4 and rheumatoid arthritis.