JAK2 and acquired polycythemia vera: In addition, JAK2 mutation is involved in activating the leukocyte and the coagulation cascade, in endothelial injury, in producing of leukocyte–platelet aggregates.[3] The presence of leukocyte–platelet aggregates and microparticles (endothelial cell platelet aggregates) in blood circulation is more common in patients with ET and PV.