Spontaneous dissociation of an IgG-3 paraprotein through disulfide interchange

A paraprotein of the gamma3 subclass was observed to dissociate "spontaneously" under various experimental conditions, such as during chromatography on DEAE-cellulose and on Sephadex G-200 or on starch block electrophoresis. This phenomenon was accompanied by the formation of various complexes of higher molecular weight, displaying antigenic properties different from those of the original paraprotein. These changes did not occur in the presence of iodoacetamide, indicating that dissociation of the paraprotein was due to disulfide interchange(s) and not to the absence of interchain disulfide bridges.