However, although FDCs are a major source of CXCL13 in LNs, monocytes and macrophages have also been shown to secrete this chemokine in the TLOs associated with rheumatoid arthritis and ulcerative colitis (Carlsen et al., 2004), suggesting additional chemokine sources in chronic inflammation, including LTo cells as noted above. The gene discussed is CXCL13; the disease is rheumatoid arthritis.