Neutrophil degranulation

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Homo sapiens
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Neutrophils are the most abundant leukocytes (white blood cells), indispensable in defending the body against invading microorganisms. In response to infection, neutrophils leave the circulation and migrate towards the inflammatory focus. They contain several subsets of granules that are mobilized to fuse with the cell membrane or phagosomal membrane, resulting in the exocytosis or exposure of membrane proteins. Traditionally, neutrophil granule constituents are described as antimicrobial or proteolytic, but granules also introduce membrane proteins to the cell surface, changing how the neutrophil responds to its environment (Borregaard et al. 2007). Primed neutrophils actively secrete cytokines and other inflammatory mediators and can present antigens via MHC II, stimulating T-cells (Wright et al. 2010).

Granules form during neutrophil differentiation. Granule subtypes can be distinguished by their content but overlap in structure and composition. The differences are believed to be a consequence of changing protein expression and differential timing of granule formation during the terminal processes of neutrophil differentiation, rather than sorting (Le Cabec et al. 1996).

The classical granule subsets are Azurophil or primary granules (AG), secondary granules (SG) and gelatinase granules (GG). Neutrophils also contain exocytosable storage cell organelles, storage vesicles (SV), formed by endocytosis they contain many cell-surface markers and extracellular, plasma proteins (Borregaard et al. 1992). Ficolin-1-rich granules (FG) are like GGs highly exocytosable but gelatinase-poor (Rorvig et al. 2009).
Literature References
PubMed ID Title Journal Year
23650620 Proteome profiling of human neutrophil granule subsets, secretory vesicles, and cell membrane: correlation with transcriptome profiling of neutrophil precursors

Heegaard, NH, Rørvig, S, Borregaard, N, Østergaard, O

J. Leukoc. Biol. 2013
17627888 Neutrophil granules: a library of innate immunity proteins

Sørensen, OE, Borregaard, N, Theilgaard-Mönch, K

Trends Immunol. 2007
1378856 Stimulus-dependent secretion of plasma proteins from human neutrophils

Nielsen, MH, Johnsen, AH, Bjerrum, OW, Borregaard, N, Kjeldsen, L, Rygaard, K, Sengeløv, H, Bastholm, L

J. Clin. Invest. 1992
20338884 Neutrophil function in inflammation and inflammatory diseases

Bucknall, RC, Wright, HL, Edwards, SW, Moots, RJ

Rheumatology (Oxford) 2010
8692836 Targeting of proteins to granule subsets is determined by timing and not by sorting: The specific granule protein NGAL is localized to azurophil granules when expressed in HL-60 cells

Le Cabec, V, Borregaard, N, Calafat, J, Cowland, JB

Proc. Natl. Acad. Sci. U.S.A. 1996
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