Recombinant Human PF-4

Platelet factor 4 (PF4) is a small cytokine belonging to the CXC chemokine family that is also known as chemokine (C-X-C motif) ligand 4 (CXCL4). This chemokine is released from alpha-granules of activated platelets during platelet aggregation, and promotes blood coagulation by moderating the effects of heparin-like molecules. Due to these roles, it is predicted to play a role in wound repair and inflammation.¹ PF4 is usually found in a complex with proteoglycan. PF4 is chemotactic for neutrophils, fibroblasts and monocytes, and interacts with a splice variant of the chemokine receptor CXCR3, known as CXCR3B.²
Platelet factor-4 is released from the alpha-granules of activated platelets and binds with high affinity to heparin. 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 probably has a role in inflammation and wound repair.³ PF4 is the antigen in heparin-induced thrombocytopenia, an idiosyncratic autoimmune reaction to the administration of the anticoagulant heparin.⁴

The biological activity of Human PF-4 was determined by its ability to inhibit human FGF-basic-dependent proliferation of NR6R-3T3 fibroblasts (Rizzino, A., et al., 1988, Cancer Res. 48:4266; Thomas, K. et al., 1987, Methods Enzymol. 147:120; Watson, J.B. et al., 1994, J. Clin. Invest. 94:261). The expected ED₅₀ for this effect is typically 5 - 15 μg/ml.

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Glu32

Lyophilized

The predicted molecular weight of Recombinant Human PF4 is Mr 7.8 kDa.

This recombinant protein was lyophilized from a 0.2 μm filtered solution in 25% acetonitrile (CH₃CN) and 0.1% trifluoroacetic acid (TFA).

This lyophilized protein is stable for six to twelve months when stored desiccated at -20°C to -70°C. After aseptic reconstitution, this protein may be stored at 2°C to 8°C for one month or at -20°C to -70°C in a manual defrost freezer. Avoid Repeated Freeze Thaw Cycles. See Product Insert for exact lot specific storage instructions.

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1. Poncz, M. et al. (1990) Blood 76: 336
2. Romagnani, P. et al. (2003) J Exp Med. 197: 1537
3. Warkentin, TE. et al. (2007) N. Engl. J. Med. 356: 891