Assessment of NETosis in patients with primary immunodeficiencies: evidence for a ROS‐independent pathway (1046.6)

Abstract

Neutrophil‐mediated host defenses against pathogens include the extrusion of a lattice of DNA and microbicidal enzymes known as Neutrophil Extracellular Traps (NETs). Since the host response of extravasated neutrophils to mycotic infections within tissues necessitates contact with extracellular matrices, this study also identified a novel and significant regulatory role for the ubiquitous matrix component fibronectin (Fn) in NET release. We report that recognition of the purified fungal‐associated molecular pattern, β‐glucan, by normal human neutrophils causes rapid (蠄 30 mins) homotypic aggregation and NET release by a mechanism that requires Fn. NET formation to Candida albicans hyphae depends on β‐glucan recognition by CR3 (CD11b/CD18), requires Fn and ERK but not production of ROS, and results in hyphal destruction. To better understand the genotypic and phenotypic correlations of NET disgorgement in the host defense we assayed responses to Fn + β‐glucan by neutrophils from various patient populations including: GATA2 deficiency, Chronic Granulomatous Disease (CGD), Leukocyte Adhesion Deficiency (LAD), STAT3 loss‐of‐function mutation, STAT1 gain‐of‐function mutation, IL‐12R β2 chain mutation, IFNγ receptor mutation, IRAK 4 deficiency, and neonatal PMNs. Surprisingly, and in contrast with previous reports, CGD and neonatal patient neutrophils formed aggregates and NETs even when treated with DPI to block residual ROS production. These data support our previous findings that the respiratory burst is dispensable for PMN aggregation and NET extrusion. Mechanisms involving STAT1, STAT3 and GATA2 may potentially mediate Fn + β‐glucan‐induced NETosis or aggregation, whereas IRAK4, IL‐12 and IFNγ do not appear to play a major role. Further studies will challenge patient cells with C. albicans to better understand mediators of phagocyte responses and help elucidate the mechanisms in rapid release of NETs to fungal pathogens.Grant Funding Source: Supported by NIH Grant GM066194; A.S. Byrd is supported by the UNCF/Merck Graduate Fellowship