Immune complexes in the pericardial fluid in systemic lupus erythematosus.

Two patients with systemic lupus erythematosus (SLE) had pericardial tamponade. The pericardial fluid from both patients contained "mixed" type cryoglobulins consisting of IgG, IgM, and C1q. There was a selective concentration of antinuclear antibodies in the pericardial fluid cryoglobulin of one patient. Pericardial fluid from the same patient contained immune complexes. Anti-DNA antibodies were found in the serum, pericardial fluid, and pericardial fluid cryoprotein. Immune complexes isolated from the pericardial fluid by polyethylene complexes isolated from the pericardial fluid by polyethylene glycol precipitation contained antinuclear antibodies including anti-DNA antibodies. Immune complexes may be important in the pathogenesis of pericarditis in SLE.