Defensin-rich granules of human neutrophils: characterization of secretory properties.
The various granule subtypes of the human neutrophil differ in propensity for exocytosis. As a rule, granules formed at late stages of myelopoiesis have a higher secretory potential than granules formed in more immature myeloid cells. Neutrophils contain four closely related alpha-defensins, which are stored in a subset of azurophil granules. These defensin-rich azurophil granules (DRG) are formed later than defensin-poor azurophil granules, near the promyelocyte/myelocyte transition. In order to characterize the secretory properties of DRG, we developed a sensitive and accurate ELISA for detection of the neutrophil alpha-defensins HNP 1-3. This allowed us to quantify the exocytosis of alpha-defensins and markers of azurophil (myeloperoxidase), specific (lactoferrin) and gelatinase (gelatinase) granules from neutrophils stimulated with different secretagogues. The release pattern of alpha-defensins correlated perfectly with the release of myeloperoxidase and showed no resemblance to the exocytosis of lactoferrin or gelatinase. This finding was substantiated through subcellular fractionation experiments. In conclusion, despite a distinct profile of biosynthesis, DRG are indistinguishable from defensin-poor azurophil granules with respect to exocytosis. Thus, in contrast to peroxidase-negative granules, azurophil granules display homogeneity in their availability for extracellular release.
The Granulocyte Research Laboratory, Department of Hematology, The National University Hospital, Rigshospitalet, Juliane Maries Vej 20, DK-2100 OE Copenhagen, Denmark. mfaurschou@rh.dk
Mikkel
M
Faurschou
Ole E
OE
Sørensen
Anders H
AH
Johnsen
Jon
J
Askaa
Niels
N
Borregaard
D000906:Antibodies; D003571:Cytochalasin B / Q000494:pharmacology; D023082:Defensins / Q000276:immunology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005089:Exocytosis; D006801:Humans; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D015203:Reproducibility of Results; D013347:Subcellular Fractions
D000906:Antibodies; D023082:Defensins; D007476:Ionophores; D003571:Cytochalasin B; D015759:Ionomycin