Human Natural Killer Cells Are Able to Kill Aspergillus Fumigatus but Not Via the Perforin - Granzyme Pathway.

Maria Bouzani*,1, Michael Ok*,2, Oliver Kurzai*,3, Hermann Einsele, MD4 and Juergen Loeffler*,5

Author address: 

1 Medizinische Klinik & Poliklinik II, Wuerzburg University, 97080, Wuerzburg, Germany, 2 Medizinische Klinik & Poliklinik II, Wuerzburg University, 97080 Wuerzburg, Germany, 3 Institut of Hygiene & Microbiology, Wuerzburg University, Wuerzburg,

Abstract: 

Poster Board I-666 Introduction: Natural killer (NK) cells are CD3- CD56+ lymphocytes demonstrating confirmed cytotoxicity against neoplastic and virus infected host cells. Increasing data provide evidence of a direct NK cell effect against extracellular pathogens, such as bacteria, parasites and yeasts, but there is a relative lack of data on their interaction with filamentous fungus and especially with Aspergillus fumigatus. Aspergillus is an omnipresent mold, living in close vicinity with humans, being constantly inhaled in the lungs and thereafter cleared by the innate immune system. Otherwise harmless for healthy people, it is at the origin of invasive Aspergillosis (IA), an extremely devastating disease for immunocompromised subjects. Host's innate immune system controls Aspergillus growth through a complex system of potent effector cells, mediating their antifungal activity mainly by phagocytosis. Our study aims to shed light for the first time on the direct interaction between human NK cells, mediators of extracellular cytotoxicity, and Aspergillus. Methods: NK cells were isolated after magnetic depletion of the peripheral blood of healthy volunteers and they were used after 24h priming with 500 U/ml recombinant interleukin 2 rhIL-2. To determine gene expression and cytokine release of interferon gamma (IFNg) and Tumor Necrosis Factor- a (TNF-a), NK cells were stimulated for 0, 3, 6 and 12h with different morphologies of Aspergillus: conidia and germlings. To evaluate the lethal impact of NK cells on Aspergillus, plate killing assays were performed at 0, 3 and 6h time points. To illustrate the role of antibody dependent cellular cytotoxicity, ADCC a monoclonal IgG antibody, against germlings, was tested. Transwell permeable membranes, with pores of 0,4 µm, prohibiting the direct contact of cells placed on their opposite sides, but allowing the free circulation of molecules, were used to estimate the effect of cell-fungal contact. To investigate the cytotoxic mechanism involved, NK cells were depleted from perforin and granzymes by treatment with strontium chloride and they had their death ligands, TNF- related apoptosis- inducing ligand (TRAIL) and FasL, neutralised by means of blocking antibodies. The release of cytotoxic granules was estimated by the NK cell surface expression of the marker of degranulation CD107a/b. Results: Observing the in vitro interaction of NK cells with Aspergillus, fungal germinated morphologies (germlings) showed to be highly immunogenic towards NK cells, compared to conidia, inducing the gene expression and cytokine release of Th1 immune mediators such as IFN-g (p
2009

abstract No: 

1640

Full conference title: 

51st American Society of Haematologists Annual Meeting
    • ASH 51st (2009)