Rituximab selectively lowers total immunoglobulin synthesis but not autoantibody content in rheumatoid arthritis (RA) synovia containing lymphoid aggregates. (a) GAPDH-normalized synovial message for IgM and IgG1 heavy constant region in RA synovial biopsies with (Aggr, n = 5) or without (None, n = 9) lymphoid aggregates 8 weeks after rituximab treatment. Serum-normalized levels of (b) total IgM and total IgG and (c) RF-IgM and anti-CCP IgG in extracts from the same synovia as in (a). Data are expressed as geometric mean ± 95% confidence interval (CI) of post-treatment levels relative to pretreatment levels. Asterisks denote that 95% CI excludes 0% change (stippled line). anti-CCP, anti-cyclic citrullinated peptide; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; RF-IgM, rheumatoid factor of the IgM subtype; SSI, synovial/serum index.