Immune response during disease and recovery in the elderly

Abstract

The present article reviews immune ageing and its relationship with nutritional ageing, with a particular insight into the influences of disease on both ageing processes. Immune ageing can be described primarily as the progressive appearance of immune dysregulations, mainly acquired immunity (mature: immature, naive: memory T lymphocyte subset decreases) leading to gradual increases in T-helper 2: T-helper 1 cells. This change is due initially to decreased thymic function, and later to accumulative antigen pressure over the lifespan. In contrast, innate immunity (macrophage functions) is preserved during the ageing process and in the elderly this leads to macrophage–lymphocyte dysequilibrium, which is particularly critical during on-going disease. Indeed, any disease induces long-lasting acute-phase reactions in aged patients and leads to body nutritional reserve (mainly protein) losses. Episodes of disease in the aged patient progressively deplete body nutritional reserves and lead to protein–energy malnutrition, undernutrition-associated immunodeficiency, and finally cachexia. Undernutrition is a common symptom in the elderly; protein-energy malnutrition is found in more than 50 % of hospitalized elderly patients and in most elderly diseased subjects. In addition, micronutrient deficit or low levels are common in home-living self-sufficient apparently-healthy elderly subjects. All these nutritional deficits induce decreased immune responses, and micronutrient deficits are now thought to be partly responsible for the decreased immune responses (immune ageing?) observed in the apparently-healthy elderly. Indeed, several studies have shown that micronutrient supplements induce increased immune responses in the healthy elderly. The progression of infectious diseases depends on immune responses and on nutritional status before the onset of illness in aged subjects. In addition, recovery depends on the intensity of acute-phase responses in the undernourished elderly. In fact, chronic acute-phase responses, commonly associated with diseases in aged patients, lead to progressive lowering of metabolic responses in the undernourished elderly. This can be quantified by increased production of free radicals during treatment and these increases may explain the difficulty in successfully treating aged patients. Nutritive therapy in order to improve metabolic processes and also to maintain body reserves should be considered as a necessary adjuvant therapy in the treatment of elderly patients.