Immunofluorescence studies of cardiac valves in infective endocarditis.

Mitral and aortic valves removed at emergency cardiac surgery from a patient with infective endocarditis caused by Streptococcus viridans were studied by immunofluorescence to ascertain the extent and pattern of various immune reactants within the large valvular vegetations. Heavy intravalvular deposits of IgG as well as bacterial antigen were present. Much more focal interstitial IgM and C3 deposits were noted within vegetations and valve substance. Diffuse endocardial and subendocardial deposition of C5b-C9 and C9 complement neoantigens was present. Direct staining of valvular tissues and vegetations for rheumatoid factor showed extensive interstitial tissue deposition. These findings emphasize the large amounts of immune reactants and constituents of immune complexes present in valves and vegetations of patients with infective endocarditis.