Platelet heparin-neutralizing factor (platelet factor 4)

The heparin-neutralizing platelet factor (PF4) is released from platelets under the influence of inducers of aggregation and nucleotide-release in the form of a high-molecular weight complex. The heparin-neutralizing activity is carried by a basic protein of molecular weight 29,700, four of which combine with a proteoglycan carrier, which in turn consists of 4 chondroitin sulfate A residues and a peptide moiety.