Effects of granulocyte colony-stimulating factor and interferon-γ on antifungal activity of human polymorphonuclear neutrophils against pseudohyphae of different medically important Candida species

Polymorphonuclear neutrophils (PMNs) are the major host defense against pseudohyphae, the invasive form of Candida species. We studied the effects of granulocyte colony-stimulating factor (G-CSF) and interferon-γ (IFN-γ) on the PMN-induced damage of pseudohyphae of Candida albicans, Candida tropicalis, and Candida parapsilosis in vitro by using two antifungal assays: a modified limiting dilution assay and a colorimetric metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. PMNs from healthy volunteers were incubated with either G-CSF (100-10,000 U/ml) or IFN-γ (10-5000 U/ml) or buffer at 37°C for 90 min and their capacity to damage nonopsonized pseudohyphae was then measured. C. tropicalis appeared to be the most susceptible species, whereas C. parapsilosis showed the highest rate of resistance to PPN damage. G-CSF (500-10,000 U/ml) and IFN-γ (100-1000 U/ml) enhanced the antifungal activity of PMNs against C. albicans pseudohyphae (P <.01 and P <.05). Among the others, G-CSF enhanced PMN-induced damage of C. parapsilosis at concentrations 500-10,000 U/ml(P <.05), whereas it enhanced damage of C. tropicalis only at 10,000 U/ml (P <.01). IFN-γ (100-1000 U/ml)-primed PMNs also caused augmented damage of C. parapsilosis (P <.05) but not of C. tropicalis at the same concentrations. Species-dependent differences exist in the responses of PMNs to Candida pseudohyphae and G-CSF as well as IFN-γ are important immunomodulators of phagocytic host defenses against them.