CXC Chemokine receptors (CXCRs) are integral membrane proteins that specifically bind and respond to cytokines of the CXC chemokine family. They represent one subfamily of chemokine receptors, a large family of G protein-linked receptors that are known as seven transmembrane (7-TM) proteins, since they span thecell membrane seven times. CXCR predominantly recognize CXC chemokines. CXC chemokines are distinguished by having four conserved cysteines, with the first two cysteines being separated by a single amino acid. There are six chemokine CXC receptors.