Immune manipulations and brain-reactive antibody formation in aging mice

Previous studies have demonstrated an increase in brain-reactive antibodies (BRA) in sera of various mammals as a function of age. The present study attempts to obtain a better understanding of the mode of formation of BRA by using various immunologic manipulations in young and old C57BL/6 mice. The mean BRA levels were significantly higher in older mice than in the young ones. Mixtures of bone marrow cells and spleen cells from old donors were able to adoptively transfer high BRA levels in young irradiated mice and this was not altered by pretreatment of the cells with anti-Thy-1.2 or anti-Ig serum plus complement. Transfer of young cells to old irradiated hosts did not lower the high BRA levels in the hosts. However, when the old hosts were also thymectomized and grafted with neonatal thymuses, BRA levels were significantly lowered. The studies tend to indicate that thymic involution or loss of thymic function in aging plays an important role in BRA formation in sera of aged mice.