The longevity of mice of the (NZB X NZW)F1 (B/W) strain and the DBA/2f strain of mice is dramatically prolonged by dietary restriction. B/W mice are susceptible to, and die at an early age from, immunocomplex nephritis. Mice of the DBA/2f strain are also relatively short-lived. Restriction of caloric intake prolonged life of B/W mice more than did protein restriction. DBA/2f mice showed prolongation of life when the diet was restricted only with respect to protein. Caloric restriction alone prolonged life less in DBA/2f mice than in B/W mice. These observations show that dietary manipulations have profound effects on immunity functions, including inhibition of the development of life-shortening autoimmune disease.