Intended for the determination of C3d complement in gel immunoprecipitation techniques, ELISA, and nephelometry.Free C3d shares epitopes with intact C3, and this necessitates the separation of free C3d from C3 and related intermediates before the immunochemical quantitation of free C3d. The separation can be performed by precipitating C3 with polyethylene glycol or with Rabbit Anti-Human C3c.