Stability of natural self-reactive antibody repertoires during aging

We have used a quantitative immunoblotting technique to analyze the repertoires of self-reactive antibodies in serum samples obtained from the same five healthy adults over a 25-year interval. The average age of the donors was 43 years at the time of the first serum sample and 69 years at the time of the second serum sample. The antibody repertoires of IgM and IgG were found to be strikingly similar among individuals in both early and late samples. Densitometric profiles of self-reactivity of serum IgM and of purified serum IgG remained unchanged over the 25-year interval. The total reactivity of serum IgG decreased significantly over the 25-year period. The observed stability of the natural self-reactive IgM and IgG antibody repertoires with aging supports the view that autoreactive B cells in the normal immune system are positively selected for reactivity with a limited set of immunodominant self-antigens throughout life.