Circulating Immune Complexes in Infective Endocarditis

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Abstract
To examine further the role of immune-complex deposition in infective endocarditis, we studied 29 patients with infective endocarditis for presence of complement-containing circulating immune complexes. Ninety-seven per cent (28 of 29) had serum levels of immune complexes greater than 12 μg per milliliter. Mean levels in these patients were significantly higher than in patients with sepsis without endocarditis or in normal controls (P<0.05). Circulating immune-complex levels were correlated with longer duration of illness (P<0.025), extravalvular manifestations of endocarditis (P<0.025) and hypocomplementemia (P<0.05). Patients with right-sided endocarditis had significantly higher circulating immune-complex levels than patients with left-sided involvement (P<0.025). In general, levels fell to zero with successful antimicrobial or surgical therapy. This drop was concurrent with disappearance of extravalvular signs, blood cultures becoming sterile, and rise in serum complement levels. These findings support the concept that immune complexes may be important in the pathogenesis of infective endocarditis. (N Engl J Med 295:1500–1505, 1976)