Antibodies reactive with streptococcal peptidoglycan-polysaccharide complexes in rheumatic fever, subacute bacterial endocarditis and tuberculosis.

Serum antibodies reactive with streptococcal peptidoglycan-polysaccharide complexes (PG-PS) have been estimated by enzyme-linked immunosorbent assay in patients with acute rheumatic fever (ARF), tuberculosis (TB) and subacute bacterial endocarditis (SBE) compared with normal age- and sex-matched controls. IgG2 and IgG3 were the predominant subclasses of antibodies in TB and SBE, whereas in ARF IgG1, IgG2 and IgG3 antibodies were detected. IgG4 antibodies were detected only infrequently. Antibodies of the IgG subclasses were detected in a greater proportion of sera when the PG-PS antigen was further purified by extraction with sodium dodecyl sulphate.