Antibody to streptococcal cell wall peptidoglycan-polysaccharide polymers in seropositive and seronegative rheumatic disease.
An ELISA has been developed for serum antibodies to streptococcal cell wall peptidoglycan-polysaccharide polymers (PG-GSP). A significantly increased prevalence of serum anti-PG-GSP antibody was found in juvenile chronic arthritis and both seropositive and seronegative rheumatoid arthritis (RA), compared with ankylosing spondylitis, systemic lupus erythematosus, myeloma and healthy controls. Anti-PG-GSP antibody was always of the IgG class and there was no correlation of anti-PG-GSP levels with C reactive protein, rheumatoid factor (RF) or anti-streptolysin O titres. There was no direct cross-reaction of RF with PG-GSP, nor did the presence of IgM-RF significantly interfere with the assay. Examination of paired serum and synovial fluid samples offered no evidence for local production of anti-PG-GSP antibody in synovial tissue. These data are compatible with an increased systemic immunization by bacterial fragments in RA.