Increase in CD5+ B cells in juvenile rheumatoid arthritis. Relationship to IgM rheumatoid factor expression and disease activity.

OBJECTIVE To investigate the association between CD5+ B cell expression and IgM rheumatoid factor (IgM-RF) in juvenile rheumatoid arthritis (JRA). METHODS CD5+ B cell levels analyzed by flow cytometry and IgM-RF expression determined by enzyme-linked immunosorbent assay were compared in children with JRA, children with other collagen vascular diseases, and healthy controls. RESULTS Children with polyarticular JRA had expanded populations of CD5+ B cells, and expansion of CD5+ B cells and IgM-RF both correlated with disease activity. CONCLUSION The results indicate that an expanded CD5+ B cell population leads to IgM-RF production in patients with polyarticular JRA, as well as patients with RA.