Polymorphonuclear functions and aging in humans.

To determine whether normal aging interferes with the functional capability of polymorphonuclear leukocytes (PMNs), 6 tests of PMN function were performed in 285 healthy subjects whose ages ranged from 20 to 97 years. A second selection based upon blood measurement and a review of medical histories 6 months later, eliminated 68 subjects. The 217 remaining persons were sub-classed by age into 7 groups including equal numbers of males and females. The functional properties of PMNs in the aged, when compared to those of younger adults, were characterized by: (a) a decrease in the chemotactic response in the 80+ age group: (b) increased adherence, with onset after age 70, maximal after age 80; (c) a progressive decrease of NBT dye reduction capability, up to age 70-79, followed by an unexplained increase of the mean value after age 80; (d) diminished Candida-killing activity, appearing in the 60+ group and becoming lowest in the oldest group; and (e) lack of changes in spontaneous migration and endocytosis. The mechanisms by which this impairment occurs are hypothetical. It is proposed that normal PMNs, after leaving the bone marrow, are influenced by various humoral components such as metabolic byproducts or immune processes altered by aging. Thus the defective PMN may represent only another victim of the aging process.