Seventeen different CXC chemokines have been described in mammals. These CXC chemokines can be divided into two classes. Among them, the chemokine with a specific amino acid sequence of glutamic acid-leucine-arginine (ELR) immediately before the first cysteine of CXC is a type (ELR Positive) and those without ELR are another type (ELR Negative). Previous studies have found that ELR-positive CXC chemokines can interact with chemokine receptors CXCR1 and CXCR2 and specifically induce neutrophil migration. ELX-negative CXC chemokines tend to attract lymphocytes.