Influence of aging and protein deficiency on neutrophil function.

This study examined the effect of age and protein deficiency on the function of mouse neutrophils. Compared with appropriate controls aging and protein deficiency caused significant reductions in respiratory burst activity, exocytosis, and enzyme release from neutrophils. Individually, neither aging nor protein deficiency caused decreases in the ability of the neutrophil to phagocytose or kill bacteria. When aged animals were fed a protein deficient diet, however, further reductions in neutrophil function occurred that resulted in significant decreases in phagocytosis and bacterial cell kill. These findings indicate that both aging and protein deficiency compromise neutrophil function. When both variables are present the abnormalities become sufficient to affect the neutrophils' most critically important functions. The results emphasize the importance of protein deficiency in the aged and help explain the high prevalence of bacterial infection in malnourished older individuals.