The Role of GBPIalpha in Phagocytosis of Platelets by Macrophages.

Abstract

Platelet storage at 04 C suppresses bacterial multiplication, but induces clusters of glycoprotein (GP) Ibalpha that trigger their phagocytosis by macrophages and reduce their survival after transfusion. We searched for a method that detects cold-induced changes in GPIbalpha involved in phagocytosis. STUDY DESIGN AND METHODS: Human platelets were isolated and stored for up to 48 hrs at 0C. Binding of a PE-labeled antibody directed against amino acids 1–35 on GPIbalpha (AN51-PE) was compared with phagocytosis of platelets by matured monocytic THP-1 cells, analyzed by FACS. RESULTS: Freshly isolated platelets were detected as a single population of AN51-PE positive particles and showed < 5% phagocytosis. Cold storage led to a decrease in AN51-PE binding and an increase in phagocytosis. N-acetylglucosamine (GlcNAc), known to interfere with macrophage recognition of GPIbalpha clusters, restored normal AN51-PE binding to cold-stored platelets and suppressed phagocytosis. CONCLUSIONS: We conclude that binding of an antibody against AA 1–35 on GPIbalpha reflects changes in GPIbalpha that make platelets targets for phagocytosis by macrophages.

Platelet responsiveness and function during storage : implications for platelet transfusion therapy

“…An in vitro phagocytosis assay, based on co-incubation of platelets with mature monocytic cells, shows that the elimination of stored platelets can be separated into three phases. 143,144 First, there is the binding of platelets to monocytes, which is in part mediated by platelet CD62 with P-selectin glycoprotein ligand-1 (PSGL-1) as counter-…”