Acquired immunological tolerance in aged mice. I. The dose-response relationship

Immunoresponsiveness declines with advancing age. In addition, there is an increase in specific and nonspecific suppressor cell activity. In view of these observations it might be predicted that aged mice would be easier to render immunologically tolerant. However, we show here that aged C57B1/6 mice are markedly more resistant to tolerance induction so that 100 times more tolerogen is required to induce unresponsiveness in 24-month-old than in 2-month-old animals. With age the variability between individuals for spleen size and sensitivity to antigen and tolerogen increases in C57B1/6 and Balb/c mice. On the other hand, the duration of tolerance is very little affected by age. The relationships between tolerance, aging and autoimmunity are discussed.