Mononuclear phagocyte system complement receptor dysfunction in rheumatoid arthritis.

To explore the relationship between complement-dependent and Fc receptor-mediated clearance mechanisms, clearance studies were performed in nine patients with definite rheumatoid arthritis and 49 normal controls. Kinetic analysis allowed evaluation of the four rate constants governing both complement- and Fc-mediated clearance processes. This analysis revealed that patients with rheumatoid arthritis had significantly reduced values for the constants regulating complement-dependent clearance (p less than 0.001). Complement-mediated clearance dysfunction was associated with normal serum complement levels and normal Fc receptor function. These data indicate that complement-mediated clearance defects are neither the simple result of a hypocomplementemic complement opsonization deficiency nor merely the reflection of profound Fc dysfunction. Defects in the two clearance processes can occur independently. These data demonstrate a specific complement receptor defect in the fixed tissue macrophages of patients with rheumatoid arthritis.