Effects of aging on the induction of experimental systemic lupus erythematosus (SLE) in mice

The study was designed to determine whether manisfestations of autoimmunity are altered with age, using an experimental model in which systemic lupus erythematous (SLE) is induced in mice. Young (2-month-old), and aging (18-month-old) BALB/c female mice were immunized with a human monoclonal anti-DNA antibody that bears a common idiotype (16/6 ld). Control groups were either left untreated or were injected with human IgM (HIgM). Anti-16/6 Id levels were found to be significantly lower in the old mice than in the young. Similarly, anti-anti-16/6 Id (murine 16/6 Id⁺) values were lower in the old. Mice injected with the 16/6 Id also produced various autoantibodies, including anti-dsDNA, anti-RNP, anti-Sm and anti-histones antibodies. The levels of these antibodies were lower in the old mice than in the young, yet the differences were not statistically significant. Levels of autoantibodies examined in control animals were either similar in both age groups (anti-RNP and histones) or lower in the old (anti-dsDNA and Sm). Four months after a booster injection of 16/6 Id, the young mice developed clinical manifestations of SLE, including proteinuria and leukopenia, which were seen, in milder form, in the aged mice. Immune complex depositions examined by immunohistology on kidney sections suggested similar differences based on the age of the animals. Our results suggest that aging might actually be associated with a decline in the capacity to produce autoimmune responses.