Lymphoproliferative responses in diet-restricted and aging Sprague-Dawley rats

Immunological effects of aging and dietary restriction (i.e., chronic underfeeding without malnutrition) were investigated in male CFY Sprague-Dawley rats. From weaning, diet-restricted animals were given the amount of food that maintained their body weights at approximately 50% of age-matched ad libitum controls. Cells from the spleen, Peyer's patches, brachial/axillary lymph nodes, and mesenteric nodes of 12- and 20-month-old rats were tested in vitro against the T-cell mitogens phytohaemagglutinin and concanavalin A, and the B-cell mitogen Salmonella minnesota lipopolysaccharide (with dextran sulphate). No clear boosting effect of dietary restriction nor age-related decline in T- or B-cell response was observed when a standard foetal bovine serum supplement was used. In general however, serum from diet-restricted rats supported better proliferative responses than serum from age-matched controls, suggesting that dietary restriction may promote lymphocyte proliferation by an indirect mechanism. A feature of this study was the variation in phenotype and immune responsiveness among closely related animals. Thus in an outbred population, any beneficial effects of dietary restriction upon immune responses could be outweighed by variation among individuals.