Alterations in immune function in rats caused by dietary lipotrope deficiency: effect of age

Weanling male Sprague-Dawley rats were maintained on a control (C), folacin-deficient (F) or marginal methionine-choline diet (M/C) for 3 weeks, 3 months or 12 months. The immunocompetence of the animals was determined by in vivo (response to infection with salmonella typhimurium) and in vitro (lymphocyte transformation assay) methods. It was found that young animals were most sensitive to dietary lipotrope deficiency, and the in vivo response to bacterial infection did not always correlate with in vitro assessment of immune function. Histopathologic examination of spleens from S. typhimurium-infected rats maintained for 3 weeks on the experimental diets showed an overall decreased cellularity especially in the follicular areas, compared to controls. No differences were seen in the spleens of infected animals at later time points. A short-term (3-week) lipotrope deficiency resulted in a depressed lymphocyte transformation response to concanavalin A (Con A) in the spleen, thymus and lymph nodes; to phytohemagglutinin A (PHA) in the spleen and lymph nodes only. After 3 months on the F or M/C diets, a depressed Con A-induced transformation response was still seen in the spleen, but the normal aging-induced immunosuppression resulted in a low response in all animals, with few significant differences existing among groups.