IgM, IgG and IgA class enterobacterial antibodies in serum and synovial fluid in patients with ankylosing spondylitis and rheumatoid arthritis.

IgM, IgG and IgA class antibodies against three Klebsiella pneumoniae capsular types, Escherichia coli and Proteus mirabilis, as well as total immunoglobulin concentrations, were measured by enzyme immunoassay and radial immunodiffusion technique, respectively, in paired serum and synovial fluid samples from eight patients with ankylosing spondylitis and 10 with rheumatoid arthritis. No clear evidence for intra-articular antibody production against any of the studied microbes was found.