CXCR1 is a 67-70 kD seven-transmembrane protein, also known as IL-8 receptor A (IL-8RA), CD181, and CDw128a. It is a CXC chemokine receptor belongs to G protein-coupled receptor (CPCR) family. CXCR1 is expressed as homodimer or heterodimer with CXCR2 and found on granulocytes, NK cells, subset of T lymphocytes, mast cells, monocytes, endothelial cells, megakarocytes, and oligodendrocytes. The expression level of CXCR1 on monocytes is lower that of CXCR2. CXCR1 mediates nurophil activation and chemotaxis, megakaryocytic proliferation, and angiogenesis via binding its ligands including IL-8(CXCL8), NAP-2(CXCL7), GCP-2(CXCL6), and GRO-alpha(CXCL1).