[Correlation of serum IgA levels with serum IgG levels, erythrocyte sedimentation rate and platelet counts in 98 patients with rheumatoid arthritis].

Rheumatoid arthritis (RA) is an autoimmune disease with unknown etiology. Polyclonal B cell activation (PBA) is one of immunological abnormalities commonly found in RA patients. We examined serum IgG, IgA, IgM levels in 98 RA patients and compared 31 patients with high serum IgA levels (group B) with 67 patients with normal serum IgA levels (group A) in clinical background. Group B patients had significantly higher mean values of serum IgG levels, erythrocyte sedimentation rate (ESR), and platelet counts than group A. However, there was no correlation between serum IgA levels and X-ray stage, class of ADL or disease duration of RA. These results indicate that high serum IgA levels reflect for disease activity of RA. Serum IgA levels did not correlate with interleukin (IL)-6 levels in 53 RA patients studied. It is speculated that high serum IgA levels might be caused by the following evidences 1) that transforming growth factor (TGF) beta, a known cytokine to increase IgA production by human splenic B cells, gene expression is enhanced in mononuclear cells from synovial fluid and 2) that iron deposition is found in RA synovial and high serum IgA levels are found in iron overload like thalassemia intermedia.