Abstract text (incl. figure legends and references)

Neutrophil extracellular traps (NETs) have been established as a key feature of cellular innate immunity that is mediated by polymorphonuclear neutrophils (PMNs), the primary leukocyte population in humans. NETs form web-like structures that are composed of DNA, histones, and antimicrobial proteins. They trap and kill microbial invaders thereby enhancing host defense. Whilst DNA has been in focus as a primary structural component of NETs, we here characterize naRNA (NET-associated RNA), as a new canonical, abundant, and largely unexplored NET component.

In order to contribute to the understanding of the localization of these RNAs and the composition of the NET structures we have analysed PMNs on the ultrastructural level both by scanning and transmission electron microscopy. Immunolabeling using anti-rRNA antibodies confirmed the presence of RNA in NET structures on ultrathin sections of plastic embedded samples corroborating fluorescence microscopy date. To show the localization of RNA to the NET structures also in SEM we established an immunolabeling protocol for this kind of samples.