Reticuloendothelial system Fc receptor function in the drug induced lupus erythematosus syndrome.

In view of reported delayed clearance of 51Cr labelled IgG sensitized autologous erythrocytes in systemic lupus erythematosus, we measured clearance half-time (t1/2) in 16 patients with the drug induced lupus erythematosus syndrome. The mean t1/2 for the patients with drug induced lupus was 52 min, and for 16 normals mean was 48 min, a difference without statistical significance. Nine of the patients with drug induced lupus had laboratory abnormalities only, and mean t1/2 in this group was not significantly different from that in the 7 symptomatic patients. T1/2 was not significantly associated with Clq or DNA binding levels in symptomatic or asymptomatic patients. Normal mean clearance of model immune complexes was thus present in patients with drug induced lupus, with and without symptoms, and may protect against renal and central nervous system disease in drug induced lupus erythematosus.

Reticuloendothelial system fc receptor function in rheumatoid arthritis.

Patients with systemic lupus erythematosus (SLE) have abnormal reticuloendothelial system (RES) IgG Fc receptor function which is correlated with disease activity and levels of immune complexes (IC). We studied RES function, IC levels, clinical and laboratory manifestations in 43 patients with RA. The articular index was abnormal in 42 patients (range of 6 to 153). Thirty were seropositive; 31 had an elevated erythrocyte sedimentation rate. Extraarticular manifestations included nodules (25), anemia (19), Sjögren's syndrome (6), vasculitis (4), and Felty's syndrome (2). Medication included corticosteroids (32), nonsteroidal antiinflammatory drugs (33), slow acting antirheumatic drugs (18), and cytotoxics (2). Thirty-three patients had IC (30 by the Clq binding assay, 21 by the Raji cell assay); 13 patients had normal RES function (t 1/2-24-60 min; upper 95% confidence limit in normals = 62 min). Thirty had prolonged clearance times (65-210 min, mean 106 min). In contrast to SLE, clearance times were not found to be correlated with IC levels, or clinical or laboratory measures of disease activity. Defective RES immune clearance may not be an important determinant in the pathogenesis of immunologic tissue damage in rheumatoid arthritis.

Activation of the alternative pathway of complement by monosodium urate crystals.

Monosodium urate crystals (MSU) have been shown to activate the alternative pathway of complement in a dose- and time-dependent fashion at 37 degrees C. Activation was maximal upon addition of 10-20 mg/ml monosodium urate crystals to C2-deficient human serum (C2D) or normal human serum containing 5 mM MgEGTA. Immunoelectrophoretic analysis of such treated sera demonstrated cleavage of C3 and factor B. Incubation of highly purified C3 and factor B with 10 mg/ml MSU did not, however, affect their immunoelectrophoretic pattern, suggesting that cleavage of either factor B or C3 in serum requires an intact alternative complement pathway. The fluid-phase control proteins, Factor H and Factor I, were not found to be diminished upon incubation of C2D serum or NHS containing MgEGTA with MSU. Thus activation appeared to be surface dependent and not a consequence of control protein depletion. It was also found, in agreement with earlier observations, that the classical complement pathway is activated, with concomitant depletion of C1 and C4. We conclude that MSU crystals activate both the classical and alternative pathways, and that such activation may participate in the pathogenesis of gouty arthritis.

Reticuloendothelial system Fc receptor function and plasmapheresis in systemic lupus erythematosus: a preliminary report.

Reticuloendothelial System (RES) Fc receptor-mediated immune clearance and levels of immune complexes were measured in patients with systemic lupus erythematosus undergoing plasmapheresis. RES clearance defects improved and disease manifestations and levels of circulating immune complexes decreased after plasmapheresis. Patients with initially abnormal reticuloendothelial system function, elevated levels of circulating immune complexes, and active acute illness appeared to respond to plasmapheresis. One patient with normal immune clearance, lacking measureable immune complexes, and manifesting chronic disease remained unchanged. Improvements seen following plasmapheresis were best maintained in patients receiving parenteral cyclophosphamide in the post-pheresis period. The correlation of clinical response, improved RES function, and decreased levels of immune complexes suggests the interaction of the latter two parameters in disease pathogenesis. Plasmapheresis has an important role as a research tool, and may be of clinical usefulness in a small number of patients with serious complications of systemic lupus erythematosus.