C-X-C motif chemokine 4 (CXCL4) also named platelet factor 4 (PF4), which is a chemokine of the intercrine alpha family. CXCL4 is a 8kDa protein containing 70 amino acid residues. CXCL4 is produced by the activated platelets which plays an important role in immune responses. CXCL4 inhibit the cell proliferation, platelet aggregation and wound repair. CXCL4 also suppresses the hematopoiesis.