INTERLEUKIN-2 PREVENTION OF APOPTOSIS IN HUMAN NEUTROPHILS

Evidence is presented that interleukin (IL)-2 maintains viability of h uman polymorphonuclear cells (PMN) in culture by preventing these cell s from undergoing programmed cell death (PCD) and induces the synthesi s of new RNA and protein. Our laboratory has recently discovered that human PMN constitutively express IL-2 beta receptor and more important ly, PMN are able to respond functionally to IL-2 by enhanced growth in hibitory activity against an opportunistic fungal pathogen, Candida al bicans. We now report that IL-2 was able to interfere with the PCD pro cess and reduce the number of apoptotic PMN IN to < 40% in 72-h cultur e. Freshly isolated PMN usually underwent a time-dependent aging proce ss and > 80% of PMN cultured in medium alone for 72 h showed morpholog ic features of PCD as depicted by hematoxylin and eosin staining as we ll as by electron microscopy. During the PCD process, untreated PMN no t only exhibited condensed nuclear structure and decrease in cell size , but also displayed DNA fragmentation. DNA fragmentation in PMN was p revented by IL-2. Prevention of PCD by IL-2 was associated with an inc rease in new RNA and protein synthesis in PMN, which map reflect cytok ine induction: such as tumor necrosis factor, as we have recently show n. Thus, our data expands our current understanding of PMN in that the y may be an active component of the immune system, with a longer life- span when activated than expected.