BINDING OF SOLUBLE IMMUNE-COMPLEXES TO HUMAN GLOMERULAR COMPLEMENT RECEPTORS

It generally is admitted that the glomerular deposition of antigen-antibody complexes merely results from their trapping by the glomerular capillary bed during the ultrafiltration process. The presence of glomerular complement receptors (GCR) on the epithelial or mesangial cells suggests that another mechanism leading to the glomerular localization of complement-bearing immune complexes could be their selective interaction with the GCR. To study the binding of immune complexes to the GCR in vitro, we determined the normal GCR binding activity with a technique recently described by Gelfand et al. After the binding conditions were standardized, we studied the GCR binding activity in the presence of increasing amounts of aggregated immunoglobulins or of DNA-anti-DNA complexes. The GCR binding activity then was measured in the presence of serum samples from patients presenting with presumed immune complex-mediated glomerular diseases. In those serum samples where the GCR binding activity was significantly reduced, the physicochemical and immunochemical properties of the causative material were characterized further. Finally, correlations were made between the GCR binding activity and the C1q binding test.