The Age‐Associated Increase in Autoreactive Immunoglobulins Reflects a Quantitative Increase in Specificities Detectable at Lower Concentrations in Young Mice

Serum immunoglobulins reactive with several autoantigens have been reported to increase with age. The authors have studied the reactivity of serum immunoglobulins from mice between 2 and 24 months of age with antigens present in lysates of syngeneic tissue extracts from young mice. The profile of immunoglobulin binding with the immunoblots of spleen and brain tissue increased progressively with age, showing only minor differences from mouse to mouse and, with one exception, revealing that the age‐associated increase in binding of immunoglobulins occurred with antigens with the same migratory position in the immunoblots detectable, at lower concentration, in sera from young mice. Not all sera from older mice had increased immunoglobulin binding when tested with extracts of skin, muscle and liver but those that did expressed increased binding with antigens in all three lysates and with the same profile shown by sera from young mice. These results are consistent with the hypothesis that the age‐associated increase in autoreactive immunoglobulins represents a selective increase in autoreactive specificities expressed by serum immunoglobulins from young animals at lower levels.