title: Fibrin mimics neutrophil extracellular traps in SEM.
abstract: Neutrophil extracellular traps (NETs) are extracellular web-like structures produced by activated polymorphonuclear neutrophils. NETs kill bacteria extracellularly, but their role in human pathology remains largely unclear. One possible way of studying NETs is through the SEM approach. However, web-like structures observed with SEM in sites of inflammation have been interpreted either as NETs or as fibrin. Thus, the question arises whether a reliable SEM discrimination between NETs and fibrin is at all possible. NET samples were collected as purulent crevicular exudate from periodontal pockets. DNase-digested controls for SEM were employed to demonstrate the DNA backbone and immuno-staining for confocal laser scanning microscopy was used to show the citrullinated histones of NETs. Blood clot samples were treated in the same way as the exudate samples to demonstrate that fibrin and fibrinolysis can mimic NETs and DNA digestion, respectively. No discrimination between fibrin and NETs based on morphological criteria in SEM was possible. Furthermore, only a vague distinction between DNA digestion and fibrinolysis could be made. These findings unambiguously indicate that the discrimination between NETs and fibrin by means of SEM is untrustworthy for samples of inflammatory exudate.
authors.affiliation: Department of Light & Electron Microscopy, Organismic Biology, University of Salzburg, Salzburg, Austria.
authors.forename: Wolf Dietrich
authors.initials: WD
authors.lastname: Krautgartner
authors.forename: Michaela
authors.initials: M
authors.lastname: Klappacher
authors.forename: Matthias
authors.initials: M
authors.lastname: Hannig
authors.forename: Astrid
authors.initials: A
authors.lastname: Obermayer
authors.forename: Dominik
authors.initials: D
authors.lastname: Hartl
authors.forename: Veronica
authors.initials: V
authors.lastname: Marcos
authors.forename: Ljubomir
authors.initials: L
authors.lastname: Vitkov
mesh_terms: D000328:Adult; D000368:Aged; D003584:Cytological Techniques; D005260:Female; D005337:Fibrin / Q000378:metabolism* / Q000648:ultrastructure; D005883:Gingival Crevicular Fluid / Q000166:cytology / Q000276:immunology / Q000382:microbiology; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D018375:Neutrophil Activation / Q000276:immunology; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology / Q000473:pathology*; D010518:Periodontitis / Q000276:immunology / Q000382:microbiology / Q000473:pathology
chemical_list: D005337:Fibrin