Multiple precipitation of sera containing monoclonal IgG proteins in radial immunodiffusion

Twenty-nine sera containing monoclonal IgG proteins have been examined by radial immunodiffusion using commercially available plates. Double precipitation by IgG myeloma sera was demonstrated to be due to the deficiency of specific antibody determinants to the Fd fragment of the monoclonal proteins.Quantitation of polyclonal- and monoclonal IgG in myeloma sera, based on ring size measurements of the two precipitation rings, leads to erroneous values. The quotient of the ring areas, however, may be useful in the evaluation of chemotherapeutic treatment.