title: Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: III. Correlative Light and Electron Microscopic Study.
abstract: Neutrophil extracellular traps (NETs) released from dead neutrophils at the site of inflammation represent webs of neutrophilic DNA stretches dotted with granule-derived antimicrobial proteins, including lactoferrin, and play important roles in innate immunity against microbial infection. We have shown the coexistence of NETs and fibrin meshwork in varied fibrinopurulent inflammatory lesions at both light and electron microscopic levels. In the present study, correlative light and electron microscopy (CLEM) employing confocal laser scanning microscopy and scanning electron microscopy was performed to bridge light and electron microscopic images of NETs and fibrin fibrils in formalin-fixed, paraffin-embedded, autopsied lung sections of legionnaire's pneumonia. Lactoferrin immunoreactivity and 4'-6-diamidino-2-phenylindole (DAPI) reactivity were used as markers of NETs, and fibrin was probed by fibrinogen gamma chain. Of note is that NETs light microscopically represented as lactoferrin and DAPI-colocalized dots, 2.5 μm in diameter. CLEM gave super-resolution images of NETs and fibrin fibrils: "Dotted" NETs were ultrastructurally composed of fine filaments and masses of 58 nm-sized globular materials. A fibrin fibril consisted of clusters of smooth-surfaced filaments. NETs filaments (26 nm in diameter) were significantly thinner than fibrin filaments (295 nm in diameter). Of note is that CLEM was applicable to formalin-fixed, paraffin-embedded sections of autopsy material.
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine , Toyoake, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Onouchi
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine , Toyoake, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Shiogama
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine , Toyoake, Japan.
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Mizutani
authors.affiliation: Techinical Support Center, JEOL Ltd., Akishima, Japan; Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Takaki
authors.affiliation: Department of Pathology, Fujita Health University School of Medicine , Toyoake, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tsutsumi
keywords: confocal laser scanning microscopy; correlative light and electron microscopy; fibrin; neutrophil extracellular traps; scanning electron microscopy