B cells support ectopic lymphoid organogenesis in rheumatoid synovitis. cDNA was generated from synovial biopsies of patients with rheumatoid arthritis, and production of CXC chemokine ligand (CXCL)13, CC chemokine ligand (CCL)21, and lymphotoxin (LT)-β mRNA was quantified by real-time polymerase chain reaction. Tissues were categorized as having germinal centers (GCs), aggregates, or diffuse infiltrates as described in Fig. 1. Results are shown as box plots with medians, 25th and 75th percentiles as boxes, and 10th and 90th percentiles as whiskers. (a) Tissues with GCs produced significantly higher levels of the tumor necrosis factor-like ligand LT-β – a molecule that is involved in lymphoid organogenesis. (b) These tissues also expressed the highest concentrations of the B cell recruiting chemokine CXCL13. (c) Similar to lymph nodes, GC-forming synovial tissues contained high levels of the T-cell attracting chemokine CCL21. Reproduced with permission . Copyright 2001, The American Association of Immunologists, Inc.