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Localization of human neutrophil interleukin‐8 (CXCL‐8) to organelle(s) distinct from the classical granules and secretory vesicles
Author(s) -
Pellmé Sara,
Mörgelin Matthias,
Tapper Hans,
Mellqvist UlfHenrik,
Dahlgren Claes,
Karlsson Anna
Publication year - 2006
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.0505248
Subject(s) - immunoelectron microscopy , biology , secretory vesicle , microbiology and biotechnology , endoplasmic reticulum , vesicle , organelle , chemokine , exocytosis , secretion , proinflammatory cytokine , cytoplast , interleukin 8 , calnexin , cytoplasm , cytokine , inflammation , immunology , biochemistry , calreticulin , immunohistochemistry , membrane
Mature human neutrophils contain small amounts of interleukin‐8 [CXC chemokine ligand 8 (CXCL‐8)], which upon proinflammatory activation, increases significantly. It has been suggested that the CXCL‐8 content of resting human neutrophils is stored in the secretory vesicles. Here, we have used a fractionation technique, which allows isolation of these vesicles, and we find that CXCL‐8 neither colocalizes with the secretory vesicles nor with markers of any of the classical neutrophil granules. To increase resolution in the system, we induced CXCL‐8 production by lipopolysaccharide. After 8 h of stimulation, CXCL‐8 was visualized within the cell using immunoelectron microscopy. The images revealed CXCL‐8‐containing stuctures resembling neutrophil granules, and these were distinct from all known neutrophil organelles, as shown by double immunostaining. Further, the CXCL‐8 organelle was present in nonstimulated neutrophil cytoplasts, entities lacking all other known granules and secretory vesicles. Upon fractionation of the cytoplasts, CXCL‐8 was found to partly cofractionate with calnexin, a marker for endoplasmic reticulum (ER). Thus, part of CXCL‐8 may be localized to the ER or ER‐like structures in the neutrophil.