Aging, nutrition and immunity – their relationship and interaction

Abstract

Demographic shifts worldwide are resulting in ever-increasing numbers of the elderly in both developed and developing countries. With aging come changes in physical and physiological integrity that are accompanied by a gradual decline in immunocompetence, commonly termed ‘immunosenescence’. Indeed, there are marked differences between young and old subjects with respect to the proportions of naïve and memory T cells and less marked differences in B cells and other immune cells. The number and proportion of late-stage memory T and B cells commonly increases, being particularly prominent in the CD8+ cytotoxic T cell pool. The accumulation of late-stage potentially “terminally” differentiated CD8+CD27−CD28−CD45RA+ cells is often considered a hallmark of immunosenescence. Malnutrition in old age can further add to the severity of this age-associated remodeling of the immune system. Age-associated obesity, in particular, is accompanied by greater chronic inflammation, as reflected in increased plasma concentrations of C-reactive protein (CRP), IL-6, TNF and other factors which may mark compromised immunity. These physiological and immunological changes accompanying aging, markedly affected by nutritional status, are likely to be different in different parts of the globe. Data suggest a gradual decline in both nutritional status and immune functions with aging, but the details of these processes, and potential differences in different societies are unclear. In the following review, we will discuss the hallmarks of age-associated immune system changes and consider how these might be affected by nutritional status.