Immunoglobulin subclass distribution of synovial plasma cells in rheumatoid arthritis determined by use of monoclonal anti-subclass antibodies.

The distribution of IgG and IgA subclass plasma cells among dissociated synovial cells from 14 rheumatoid arthritis (RA) synovia was examined by immunofluorescence using mouse monoclonal anti-human subclass antibodies. Of the IgG plasma cells 81 +/- 9% were IgG1, 4 +/- 2% IgG2, 14 +/- 9% IgG3, and 0.9 +/- 0.6% IgG4. While IgG1 predominated in all 14 synovia (which is similar to what is seen in normal tissues), in 5/14 20% or greater of IgG plasma cells were IgG3, suggesting a selective increase in IgG3 production in the synovia of certain RA patients. Among IgA plasma cells 89 +/- 5% were IgA1 and 8 +/- 3% were IgA2. This distribution is similar to the distribution in normal serum.