Reduced immune function and malnutrition in the elderly

An important observation in elderly subjects is their susceptibility to inf ection associated with a decline in host immune function. Nutrition is also an important factor that influences host defense against infection. We, th erefore, evaluated the relationship between nutritional status in 155 healt hy subjects ranging in age from 20 to 99 years and various immunological pa rameters, including the phagocytic and bactericidal activities of neutrophi ls and monocytes, superoxide production and chemotaxis of neutrophils, lymp hocyte subsets, blastoid transformation and serum immunoglobulins. Aging wa s associated with increased phagocytic activity of neutrophils but not bact ericidal activity, superoxide production or chemotaxis of neutrophils, Agin g was also associated with a significant decrease in the number of lymphocy tes as well as a decline in mature T cells and helper/inducer T cells but w ith increased numbers of activated T cells, suppressor T cells and natural killer cells. In addition, blastoid transformation in response tc, phytohem agglutinin (PRA) and concanavalin A (Con A) was significantly reduced in ag ed subjects. A poor nutritional status was noted in individuals 60 years of age or older, The nutritional status did not influence neutrophil function but correlated significantly with the number of lymphocytes and degree of blastoid formation with PHB and Con A stimulation. Our results suggest that the cell-mediated immunity in elderly subjects is reduced as a result of m alnutrition, and that improvement of the nutritional status may enhance the immune function, likely contributing to their successful aging.