IGG1 - AS THE ONLY SUBCLASS OF HUMAN SERUM IGG - SPONTANEOUSLY UNDERGOES O-2(-)-INDUCED, NONCOVALENT SELFAGGREGATION UPON STORAGE AT ROOM-TEMPERATURE

An apparent gradual decrease of IgG1 serum levels of up to 40% occurs within 48 h of storage at room temperature. The effect does not concer n any other IgG subclass, and is more pronounced in sera of smokers. A linear correlation was found between the extent of this ''storage eff ect'' and the initial concentration of IgG1, which rules out an enzyma tic process following Michaelis-Menten kinetics. PAGE and Western blot s of density gradient separated serum proteins revealed the presence o f noncovalent self aggregates of IgG1 in stored sera. Addition of supe roxide dismutase prevented both the formation of aggregates as well as the decay of IgG1 values. It is concluded that the instability of IgG 1 is due to an enhanced propensity of this molecule to form self-aggre gates, whereby O-2(-)-radicals play a functional role. This mechanism, however, is not relevant to a previously detected selective decrease of relative IgG1 levels in sera of patients afflicted with malignant d iseases of various tissue origin.