Effect of age on human neutrophil function

Neutrophil phagocytosis, reactive oxygen intermediate production (intra- an d extracellular), neutrophil bactericidal activity, and chemotaxis/chemokin esis were assessed in three age groups: 21-36, 38-56, and 62-83 years. A si gnificant age-dependent reduction in the number of phagocytized Escherichia coli per neutrophil (measured by acridine orange staining) and Staphylococ cus aureus phagocytosis (measured by flow cytometry) was seen (r = 0.669 an d r = 0.684, P < 0.001 for both). These findings correlated with an age-dep endent increase in intracellular calcium concentrations in resting neutroph ils (r = 0.698, P < 0.001) and a reduced hexose uptake (r = 0.591, P < 0.01 ), In addition, a significant reduction in the intracellular reactive oxyge n production was seen after stimulation with S. aureus (P < 0.001) with inc reasing age, In contrast, no differences between the groups in reactive oxy gen production was seen after stimulation with E. coli, The neutrophil bact ericidal activity was impaired with increasing age (64 +/- 4% of the phagoc ytized bacteria were killed in group 1.; 66 +/- 2 in group 2, and 59 +/- 6 in group 3; P < 0.01), In addition, a trend toward a reduced neutrophil che motaxis was seen with increasing age (P = 0.022), The findings suggest that increased intracellular calcium concentrations in resting neutrophils and/ or a reduced hexose uptake result in reduced phagocytic ability and decreas ed bactericidal activity of neutrophils in the elderly.