title: Radioimmunoassay evaluation of anti-C3d reactivity in broad spectrum commercial antiglobulin reagents.
abstract: The study was undertaken to assess the potential of a labeled C3d radioimmunoassay method as a standardization criterion for antiglobulin reagents containing anti-C3d reactivity. Over an 18-month interval, four different lots of broad-spectrum antiglobulin reagents were purchased from each of seven United States manufacturers. Anti-C3d antibody concentration and Ko in each lot were assayed initially and at four-month intervals over 16 to 21 months storage at 4 degrees C. The results permitted 1) comparison of anti-C3d antibody concentrations among different manufacturers, 2) comparison among different lots from the same manufacturer, and 3) assessment of stability of anti-C3d during storage. In addition, serial dilutions of reagents in each manufacturer's diluent were compared for their anti-C3d agglutinating properties by the spin-antiglobulin method against red blood cells (RBC) coated by C3d in vitro and against in vivo C3d-coated RBC from 16 patients. Most reagents were shown also to contain anti-C3c, anti-C4c and anti-C4d reactivities when tested against suitably coated RBC. Anti-C3d antibody concentrations ranged from approximately 1 to 3.5 microgram/ml for 27 of the 28 reagents and were stable over 16 to 21 months of storage. Anti-C3d agglutination titer scores showed a general correlation with anti-C3d antibody concentrations when tested against in vitro C3d-coated RBC; correlations were less good against C3d-coated cells from patients. The radioimmunoassay provided reproducible objective measurements and appeared to have merit as a standardization criterion.
mesh_terms: D000744:Anemia, Hemolytic, Autoimmune / Q000276:immunology; D000906:Antibodies / Q000032:analysis*; D000888:Antibodies, Anti-Idiotypic; D003176:Complement C3 / Q000032:analysis / Q000276:immunology*; D015932:Complement C3c; D015933:Complement C3d; D003298:Coombs Test; D004355:Drug Stability; D006801:Humans; D007202:Indicators and Reagents / Q000032:analysis / Q000592:standards; D011863:Radioimmunoassay
chemical_list: D000906:Antibodies; D000888:Antibodies, Anti-Idiotypic; D003176:Complement C3; D007202:Indicators and Reagents; D015932:Complement C3c; D015933:Complement C3d