Loss of GM1 surface expression precedes annexin V-phycoerythrin binding of neutrophils undergoing spontaneous apoptosis during in vitro aging.
BACKGROUND
Apoptosis of neutrophil granulocytes is an important determinant of the resolution of inflammation. Apoptotic neutrophils undergo specific alterations in their receptor profiles. These alterations are likely to contribute to the characteristic functional silencing of the dying cells.


METHODS
By flow cytometry and fluorescence microscopy, we analyzed the ganglioside GM1, a lipid raft marker, with respect to its surface expression on neutrophil and eosinophil granulocytes. Apoptosis was monitored by morphological changes and by the binding of annexin V-phycoerythrin (AxV-PE).


RESULTS
GM1, which was stained by the cholera toxin subunit B, was found only on neutrophil granulocytes; eosinophil granulocytes did not bind cholera toxin subunit B. GM1 was lost from the surfaces of neutrophils before AxV-PE binding (early apoptosis). Surprisingly, GM1 reappeared during the late stages of apoptosis, although without functional consequences. GM1 was found on the cell surface and in intracellular membranes, whereas CD16 was found only at the cell surface.


CONCLUSIONS
Loss of surface GM1 is a new marker for the detection of the aging of neutrophils. Its loss precedes the binding of AxV-PE of neutrophils.
Sheriff
Ahmed
A
Institute for Clinical Immunology, Department of Medicine III, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany.
Gaipl
Udo S
US
Franz
Sandra
S
Heyder
Petra
P
Voll
Reinhard E
RE
Kalden
Joachim R
JR
Herrmann
Martin
M
D017304:Annexin A5 / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D016922:Cellular Senescence / Q000502:physiology*; D004804:Eosinophils / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D005677:G(M1) Ganglioside / Q000096:biosynthesis*; D006801:Humans; D066298:In Vitro Techniques; D008856:Microscopy, Fluorescence; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology; D010799:Phycoerythrin / Q000378:metabolism*
D017304:Annexin A5; D010799:Phycoerythrin; D005677:G(M1) Ganglioside