Histone (extracellular, neutrophil-derived) and neutrophil extracellular trap (NET; (for histone, abbreviations are H2A, H2B, H3, H4 individually))

Histones (notably H2A, H2B, H3, and H4) are highly conserved nuclear proteins essential for DNA packaging within cells. When released extracellularly, commonly as a major component of neutrophil extracellular traps (NETs), histones gain potent antimicrobial and immunomodulatory properties[1][2][3][4][6]. NETs are web-like structures composed of decondensed nuclear DNA, histones, and neutrophil proteins, extruded by neutrophils during immune activation[3][4][6]. These complexes immobilize and neutralize pathogens extracellularly, act as pro-inflammatory agents, and, when dysregulated or in excess, contribute to tissue damage and drive pathology in various infectious, autoimmune, inflammatory, and thrombotic diseases[1][3][4][5][6]. Extracellular histones, whether NET-bound or free, display direct cytotoxicity to mammalian cells, promote inflammation, thrombosis, and can act via Toll-like receptors (such as TLR2) to drive T cell (Th17) differentiation. While their physiological purpose is host defense, targeting of NETs and extracellular histones is an emerging therapeutic area in diseases where their overactivity is pathogenic[1][4][6].

Other names

Histone (when referring to individual proteins: Histone H2A, Histone H2B, Histone H3, Histone H4)Neutrophil extracellular trapNETExtracellular histone

DNase I: Degrades NET DNA backbone, reduces NET burden and sputum viscosity[2] Heparin: Neutralizes positive charges on histones, reduces cytotoxicity and pro-thrombotic activity[4] Pentraxin 3: Binds extracellular histones to suppress their cytotoxicity[4]