A simple quantitative assay of circulating immune complexes by laser nephelometry, using a rabbit igg antibody against human aggregated igg.

Circulating antigen-antibody complexes were detected by measuring agglutination of complexes with rabbit antisera against heat-aggregated human IgG by means of laser nephelometry. Rabbit antisera were obtained by immunization with heat-aggregated human IgG after intravenous injection of a large amount of native human IgG. The antisera were observed to be almost specific to conformationally altered human IgG by immunodiffusion. Even if the antibody activity to native IgG did occur in the antisera, the native IgG in test sera was in excess of antigen in the assay system employed for the detection of immune complexes. In conclusion, the minor antibody activity against native IgG does not interfere with the assay of immune complexes by laser nephelometry. The clinical applications demonstrated the advantage of the method.