Subclasses IgA1 and IgA2 in serum and synovial fluid in rheumatoid arthritis and reactive synovitis of local origin.

Subclasses IgA1 and IgA2 in serum were examined in 40 patients (28 cases of rheumatoid arthritis and 12 cases of reactive synovitis of local origin) and also in synovial fluid of the knee joint in 17 of these patients. The levels of IgA1 and IgA2 in serum were statistically significantly higher than in synovial fluid in both groups of patients (P = 0.0237--0.0018), but significant correlations between serum and synovial fluid for IgA1 (R = 0.8855, P = 0.0010) and for IgA2 (r = 0.7630, P = 0.0124) were found only in cases of rheumatoid arthritis. A percentage evaluation revealed a significant disproportion (P = 0.0028) in favour of IgA1 in synovial fluid during rheumatoid arthritis. The analysis of proportions of IgA subclasses and rheumatoid factor has shown no significant relationships.