Influence of age on polymorphonuclear leukocytes in vitro: phagocytic activity in healthy human subjects.

Polymorphonuclear leukocytes (PMNs) represent an important defensive mechanism against infectious agents. Some of their functions are impaired in old people, with a decreased effectiveness of nonspecific immunity. In vitro PMN phagocytic activity was studied with different techniques on 74 healthy subjects (20-82.5 years; 40 males, 34 females). Serum-mediated ingestion resulted to be impaired with age with a lower ratio of active PMNs and a lower activity of phagocytosing cells. The behavior of these parameters was age-related, without significant difference between males and females; the decline was found to be a continuous phenomenon with no threshold age. Serum-independent ingestion had very low values and was not impaired with aging. The present data can represent a further explanation for the finding of a higher incidence and mortality of bacterial diseases in elderly population.