Interleukin-8 (IL-8), also known as CXCL8, is a chemokine that is upregulated at sites of inflammation where it promotes neutrophil infiltration and activation. IL-8 can form homodimers and heterodimers with CXCL4/PF4. Its bioactivity is regulated by proteolytic truncations, citrullination, and the decoy receptor DARC. IL-8 signals through CXCR1/IL-8 RA, which is also used by CXCL6, and through CXCR2/IL-8 RB, which is used by multiple CXC chemokines. IL-8 also binds to Serpin A1/alpha-1 Antitrypsin which prevents IL-8 interaction with CXCR1.