Background: Polymorphonuclear granulocytes (PMNs) are important effector cells in the immune response against fungal infections. To elucidate mechanisms responsible for inactivation of pathogenic fungi by PMNs, the interaction of these cells with A. fumigatus (conidia and germinating conidia) and C. albicans (blastoconidia and germtubes) was analysed. Methods: PMNs (purity ~ 90%) were isolated from the blood of healthy human volunteers directly before use. Fungi were co-cultured with PMNs (1-4 hours) for quantification of the oxidative burst, the efficiency of fungal damage and the formation of neutrophil extracellular traps (NETs). Each experiment was repeated at least 3 times with PMNs from different donors. Results: C. albicans was a more potent inducer of reactive oxygen intermediates (ROI) than A. fumigatus. Furthermore, the level of ROI produced by PMNs was strongly dependent on the fungal morphotype. Only hyphal forms of both fungi were found to induce a strong oxidative burst, independent of their viability. This effect was not due to a higher biomass of the hyphal forms. Actin rearrangement and most likely phagocytosis are necessary for efficient generation of ROI. TNF-a, GM-CSF, IL-1beta and IL-4 enhanced the oxidative burst. A similar effect was detected for the immune regulatory drug mycophenolate. Fungal damage induced by PMNs occured mainly with in the first hour. However, as increased ROI production did not result in enhanced killing, ROI may play only a minor role in fungal inactivation. Extracellular killing might occur predominantly by NETs, which are formed in response to A. fumigatus and C. albicans. Conclusions: PMNs attack fungi in different ways and the generation of ROI plays only a minor role in destroying fungal pathogens. The reaction patterns of PMNs towards fungi can be affected by cytokines and immunomodulatory drugs.
Full conference title:
46th Interscience Conference on Antimicrobial Agents and Chemotherapy
- ICAAC 46th