Rheumatic-like carditis induced in rabbits by cross-reacting antigens: Streptococcus A polysaccharide and rabbit...

A rheumatic-like carditis was induced in rabbits by 8 mo of immunization with small doses of Streptococcus A polysaccharides or peptoglycane and rabbit aortic glycoprotein. Cardiac lesions were detected 5 to 6 mo after the beginning of immunization and were preceded by the appearance of circulating antibodies. The immunopathological study with peroxidase-labeled antibodies indicated the binding of IgG and C3 complement to the damaged cardiac areas. Enzyme-labeled antibodies to streptococcal polysaccharides were bound to the connective tissue of the cardiac valves and the coronary vessels. An immunological cross-reactivity was detected between Streptococcus A polysaccharide and aortic glycoprotein; this suggests that the immunopathological process initiated by the streptococcal infection may subsequently involve the cardiac tissue itself.