Platelet factor 4 (PF4)

Released during platelet aggregation. Neutralizes the anticoagulant effect of heparin because it binds more strongly to heparin than to the chondroitin-4-sulfate chains of the carrier molecule.

Chemotactic for neutrophils and monocytes. Inhibits endothelial cell proliferation, the brief form is a stronger inhibitor than the longer form.