Feline complement dependent binding in the Raji cell assay is insufficient for the quantitation of immune complexes

A comparison was made of the binding of radiolabeled heat aggregated cat immunoglobulin G (125I-ACG) to Raji cells using normal or heat-inactivated cat or human serum. The binding with normal or heated cat serum, as well as heated human serum were essentially identical. The binding using normal human serum was 2.5- to 3-fold greater than observed with heated human serum. These results suggest that feline complement associated with 125I-ACG does not bind to Raji cells via complement receptors, but only by receptors for the Fc portion of IgG. Human serum and 125I-ACG can bind to both Fc and complement receptors on Raji cells.