Analysis of the IgG subclass production from rheumatoid arthritis synovial cell cultures.

In man there are four subclasses of IgG which differ from each other with respect to their biological properties. Some evidence suggests that the production of IgG3 is unusually high in rheumatoid synovia. In this study secretion of IgG subclasses by synovial lymphocytes in vitro was measured using sensitive subclass-specific ELISAs. It was found that, in both synovial membrane- and synovial fluid-derived cell cultures, the general pattern of IgG subclass secretion was IgG1 greater than 2 greater than 3 greater than or equal to 4, and that, in most cultures, IgG3 was a minor subclass accounting, on average, for only 8% of the total IgG. This was similar to the percentage of this subclass in normal human serum and in culture supernatants from the patients' peripheral blood lymphocytes.