Role of glycoprotein Ibalpha in phagocytosis of platelets by macrophages.
BACKGROUND
Platelet (PLT) storage at 0 to 4 degrees C suppresses bacterial multiplication, but induces clusters of glycoprotein (GP) Ibalpha that trigger their phagocytosis by macrophages and reduce their survival after transfusion. A method was sought that detects cold-induced changes in GPIbalpha involved in phagocytosis.


METHODS
Human PLTs were isolated and stored for up to 48 hours at 0 degrees C. Binding of a phycoerythrin (PE)-labeled antibody directed against amino acids (AA) 1-35 on GPIbalpha (AN51-PE) was compared with phagocytosis of PLTs by matured monocytic THP-1 cells, analyzed by fluorescence-activated cell sorting.


RESULTS
Freshly isolated PLTs were detected as a single population of AN51-PE-positive particles and showed less than 5 percent phagocytosis. Cold storage led to a decrease in AN51-PE binding and an increase in phagocytosis. N-Acetylglucosamine, known to interfere with macrophage recognition of GPIbalpha clusters, restored normal AN51-PE binding to cold-stored PLTs and suppressed phagocytosis.


CONCLUSIONS
It is concluded that binding of an antibody against AA 1-35 on GPIbalpha reflects changes in GPIbalpha that make PLTs targets for phagocytosis by macrophages.
Badlou
Bahram A
BA
Thrombosis and Haemostasis Laboratory, DCCH, the Department of Immunology, UMC-Utrecht, the Institute for Biomembranes Utrecht University, and the Sanquin Blood Bank Region North-West, Utrecht, the Netherlands.
Spierenburg
Gerrit
G
Ulrichts
Hans
H
Deckmyn
Hans
H
Smid
W Martin
WM
Akkerman
Jan-Willem N
JW
D000117:Acetylglucosamine / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001792:Blood Platelets / Q000502:physiology*; D005374:Filtration; D006801:Humans; D008264:Macrophages / Q000276:immunology*; D010587:Phagocytosis; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000502:physiology*
D000911:Antibodies, Monoclonal; D019038:Platelet Glycoprotein GPIb-IX Complex; D000117:Acetylglucosamine