Antifungal activity of human polymorphonuclear leucocytes against yeast cells of Paracoccidioides brasiliensis

Human peripheral blood polymorphonuclear leucocytes (PMN) were examined in vitro for antifungal activity against yeast cells of Paracoccidioides brasi liensis. The yeast cell of this fungus was resistant to killing by PMN, How ever, PMN exhibited a fungistatic effect on the fungal isolates employed in a long-term (similar to 72 h) assay. Lysates of PMN did not show a fungist atic or fungicidal effect, indicating that live PMN are necessary for the a ntifungal effect. Interferon-gamma (IFN-gamma) enhanced the antifungal acti vity of PMN, IFN-gamma-treated PMN killed isolate Bt-4 within 2 h of cocult ure, and after 24 h a still greater killing effect was observed. By contras t, IFN-gamma-treated PMN did not show a significant killing effect on isola te Tatu, but did exhibit an enhanced fungistatic effect on this isolate. In contrast, tumor necrosis factor-alpha and interleukin 8 had no effect on t he antifungal activity of PMN. Scanning electron microscopy revealed that t he surface structure of the fungal cell was apparently damaged by PMN withi n 24 h of cocultures. Based on these novel findings, we speculate that huma n PMN might play a role in host resistance in early infection with this fun gus due to their antifungal activity.