Platelet factor 4 (PF4) is a 70-amino acid protein belonging to the CXC chemokine family also known as chemokine (C-X-C motif) ligand 4 (CXCL4) . It is released from the alpha-granules of activated platelets during platelet aggregation, and promotes blood coagulation by moderating the effects of heparin-like molecules. PF4 is chemotactic for neutrophils, fibroblasts and monocytes, and interacts with a splice variant of the chemokine receptor CXCR3, known as CXCR3B. Its major physiologic role appears to be neutralization of heparin-like molecules on the endothelial surface of blood vessels, thereby inhibiting local antithrombin III activity and promoting coagulation. As a strong chemoattractant for neutrophils and fibroblasts, PF4 plays a critical role in inflammation and wound repair. PF4 is the antigen in heparin-induced thrombocytopenia, an idiosyncratic autoimmune reaction to the administration of the anticoagulant heparin. Its autoantibodies have been found in patients with thrombosis and features resembling HIT but no prior administration of heparin.
血小板因子4抗体