IgG subclass composition of rheumatoid arthritic sera and joint fluids

The IgG subclass composition of 24 matched pairs of synovial fluids and sera, from 24 patients with rheumatoid arthritis, was determined. The subclass composition of rheumatoid synovial fluid IgG was found to be qualitatively the same as that of the corresponding serum, differing only in certain quantitative aspects. A 7-8% increase in IgG1 level found in the sera of rheumatoid arthritis patients relative to that in the sera of normal individuals was accompanied by 6-8, 0-7, and 0-3% decreases in IgG2, IgG3, and IgG4, respectively.