RA synovial tissue has been shown to be rich in CXCL12, which is produced by fibroblast-like synoviocytes (27), and this chemokine plays an essential role in B cells resistance to apoptosis, and supports the hypothesis that these synovial cells are involved in the homing and survival of B cells (28). This evidence concerns the gene CXCL12 and rheumatoid arthritis.