Non-specific immunity in aging: deficiency of monocyte and polymorphonuclear cell-mediated functions.

Peripheral blood monocytes obtained from 55 aged donors were evaluated for their chemotactic and phagocytic capacity. In the same subjects, polymorphonuclear cell-mediated functions were studied by chemotaxis, phagocytosis, nylon fiber adherence and nitroblue-tetrazolium reduction assay. Monocytes showed a normal chemotactic responsiveness to zymosan-activated serum, while the chemotactic activity induced by leukocyte-derived chemotactic factor and phagocytosis were rather depressed. A dramatic impairment of polymorphonuclear cell-mediated immune response was also observed. In fact, in spite of a normal nylon fiber adherence, chemotaxis, phagocytosis and nitroblue-tetrazolium reduction capacity were significantly depressed by the aging process. These data suggest that the deficiency of non-specific immunity may play an important role in the increased susceptibility to infections in aged donors.