Inhibitor of angiogenesis. Inhibitor of endothelial cell chemotaxis (in vitro). Homotetramer. The N-terminal processed forms of platelet factor 4 variant seems to be produced by proteolytic cleavage. The most abundant form is Platelet factor 4 variant(5-74). Platelet factor 4 variant. Platelet factor 4 variant(4-74). Platelet factor 4 variant(5-74). Platelet factor 4 variant(6-74). Binding to heparin is much weaker than in the close homolog PF4/CXCL4. Belongs to the intercrine alpha (chemokine CxC) family.