TNF and rheumatoid arthritis: CXCL13, a chemokine that attracts B lymphocytes and follicular helper T lymphocytes (TFH) by binding to C-X-C chemokine receptor type 5 (CXCR5), is upregulated in a subset of T cells by TNF or interleukin 6 (IL-6) in RA [14, 15] as well as in follicular dendritic cells in the germinal center of lymphoid tissues [16].