Serum and tissue immune complexes in infective endocarditis.

Serial circulating immune complex (IC) determinations were performed in 24 patients with infective endocarditis (IE) using the solid phase Clq, solid phase conglutinin and 3.5% polyethylene glycol precipitation assays. Circulating IC were detected in 67% of IE patients at presentation, but in only 7% of valve lesion controls. Serial determinations produced a 75% prevalence of IC in IE. The presence of circulating IC correlated with "subacute" disease, the presence of tissue deposits of immunoglobulin and/or complement components and with certain extravalvular manifestations (immune complex type glomerulonephritis cutaneous vasculitis and musculoskeletal manifestations). Effective therapy was associated with a fall in circulating IC levels, an effect which was well demonstrated by 3 patients in whom IC rapidly fell to zero following artificial valve replacement. The results support a role for circulating IC in the pathogenesis of this disorder, and suggest that serial IC determinations are useful in following clinical progress, particularly in culture negative endocarditis.