Tumor necrosis factor alpha potentiates neutrophil antimicrobial activity: increased fungicidal activity against Torulopsis glabrata and Candida albicans and associated increases in oxygen radical production and lysosomal enzyme release

Abstract

The capacity of human tumor necrosis factor alpha (TNF-alpha) to modulate the killing of the opportunistic pathogens Torulopsis glabrata and Candida albicans by human neutrophils was studied. TNF-alpha significantly enhanced neutrophil fungicidal activity in a concentration-dependent manner and was evident in a range of neutrophil-fungus ratios. Enhanced killing of T. glabrata required much lower TNF-alpha concentrations than were required for enhancement of killing of C. albicans. Maximal enhancement of killing occurred with 20 and 100 U of TNF-alpha per 5 x 10(6) neutrophils for T. glabrata and C. albicans, respectively. The fungal killing kinetics demonstrated that TNF-alpha augmentation of fungicidal activity was evident within 1 h and persisted for an incubation period of at least 22 h. Preincubation of neutrophils with TNF-alpha was essential for the enhancement of killing. Maximal stimulation of killing was observed within 1 h of preincubation with TNF-alpha, and poor stimulation of killing was observed when TNF-alpha was added at time zero. Associated with the increase in fungicidal activity was an increased production of superoxide and an enhanced degranulation of enzymes and other proteins from azurophilic and specific granules in response to the fungi. The results demonstrate that TNF-alpha augments the neutrophil oxidative respiratory burst and the degranulation induced by opsonized fungi and that it increases the neutrophil fungicidal activity.