Increase in CD5+ B Cells in Juvenile Rheumatoid Arthritis

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 enzymelinked 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.