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

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.

Experimental nephropathy induced in the rabbit by immunization with a lipopolysaccharide from Escherichia coli.

Twenty rabbits were each injected with 100 microgram of lipopolysaccharide from Escherichia coli 055 at weekly intervals for up to 15 months. The antisera showed an immunologic cross-reactivity with rabbit kidney glycoprotein. A macroscopic nephropathy was present in 14 of the 17 rabbits in which the kidneys were examined. All the rabbits showed extensive histologic lesions involving all the structures of the kidney: organized thrombosis of the arteries, extensive areas of infarction, glomerular atrophy, tubular necrosis and proliferation of young connective tissue. A marked infiltration with lymphoid cells and some plasmacytes was present. The immunologic character of this nephropathy and the immunopathogenic mechanism involved in its pathogenesis are discussed.