Coexistence of Multiple Monoclonal Immunoglobulins with Identical Constant Regions in One Patient

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Abstract
Two populations of IgG molecules, designated F-IgG3(.kappa.) and S-IgG3(.kappa.), were isolated from a patient with multiple myeloma. The constant regions of the 2 molecules appear to be identical, since the H chains of both belong to the .gamma.3 subclass, and both molecules were positive for G3m(5), G3m(10) and G3m(11), but negative for G3m(21), Km(1) and Km(2) allotypes. The 2 molecules have different variable regions, since they do not share idiotypic determinant(s); their L chains have different NH2 terminal amino acid sequences; and both their H and L chains have different peptide maps and amino acid compositions. SDS[sodium dodecyl sulfate]-polyacrylamide gel electrophoresis showed that the F-IgG3(.kappa.) molecules have 2 kinds of L chains. One, designated .kappa.n, had a normal MW (.apprx. 23,000); the other, designated .kappa.h, had a MW of .apprx. 28,000.