Brewer's Yeast Supplementation Enhances Immune Response of Aged Mice

A large amount of evidence indicates that aging is associated with immune system dysfunction. Brewer's yeast, one of the most notable species of yeast in health and wellness, has been shown to stimulate the immune system and improve human life span. In the present study, brewer's yeast (5, 25 or 125 μg/mouse) was orally supplemented to aged mice each other day for 4 weeks. Total number of leukocytes from peripheral blood (PBl), thymus (Thy), spleen (Sp), and peritoneal exudate cells (PEC) were counted. Carbon clearance, plaque-forming cell and rosette-forming cell assays were used to measure macrophage, B cell and T cell responses. In vitro proliferation of splenocytes and histological architecture of thymus from aged mice were tested. Yeast treated mice showed a significant increase in the total number of PBl leukocytes, total cellularity of both Thy and Sp, as well as a significant increase in total and differential numbers of PEC. A gradual increase in macrophages' phagocytic activity of PEC and a significant increase in both plaque-forming cell and rosette-forming cell responses were observed. In vitro results showed that incubation of splenocytes with brewer's yeast (0.5, 2.5 or 12.5μg/well) in the presence of concanavalin-A mitogen elicited a gradual increase in the proliferation of splenocytes. Histological examination of thymuses from yeast-treated aged mice revealed that the cortex was preferentially enlarged and repopulated with immature thymocytes. These results indicate that brewer's yeast supplementation to aged mice improves several baseline immune responses, and provides a valuable tool to identify nutritional strategies that could mitigate immunosenescence.