Synovial fluid in seronegative juvenile rheumatoid arthritis: studies of immunoglobulins, complements, and alpha 2-macroglobulin.

Synovial fluid of 20 children with seronegative juvenile rheumatoid arthritis (JRA) and 20 patients with other joint pathology was examined for levels of total hemolytic complement and selected components, immune complexes, and alpha 2-macroglobulin (alpha 2-M). When adjusted for total protein, synovial levels of total hemolytic complement, C3, C4, and alpha 2-M did not differ significantly in the two groups. The concentrations of IgM and IgG were elevated in the JRA synovial fluid, but immune complexes were not increased when compared with non-JRA group as determined by the Raji cell technique. alpha 2-M activity against substrates of C1 esterase was absent. therefore, evidence of specific increase in immune complexes and complement activation was sought but not found, suggesting that they may not be a major factor in the pathogenesis of seronegative, pauciarticular JRA.