ANALYSIS OF THE NATURAL HUMAN-IGG ANTIBODY REPERTOIRE - LIFELONG STABILITY OF REACTIVITIES TOWARDS SELF-ANTIGENS CONTRASTS WITH AGE-DEPENDENT DIVERSIFICATION OF REACTIVITIES AGAINST BACTERIAL-ANTIGENS

We used a quantitative immunoblotting technique to analyze the reperto ires of IgG antibody reactivities in the serum of healthy young childr en, young adult males and aged males with self and non-self antigens. Densitometric patterns of reactivity of purified IgG with self antigen s were highly conserved between individuals within a given age group a nd across age groups. Inter-individual differences were observed, howe ver, upon analysis of self reactivities of IgG in whole serum. A strik ing heterogeneity between individuals within a given age group and acr oss age groups characterized the reactivity of purified IgG and of IgG in whole serum with bacterial antigens. Inter-individual differences were more marked among aged individuals than among individuals of othe r age groups. Analysis of variances of reactivities of IgG with bacter ial antigens further demonstrated an increased diversity of repertoire s of aged donors compared with those of young adults and children. Our results document the stability of the self-reactive repertoires of Ig G throughout life, which contrasts with the diversification of the rep ertoire of IgG antibody reactivities directed toward foreign antigens with aging. These findings support the concept that self-reactive anti body repertoires are positively selected throughout life by a restrict ed set of self antigens shared by all individuals.