Interleukin 8 (IL-8), a member of the neutrophil-specific CXC subfamily of chemokines, is a potent neutrophil chemotactic and activating factor. It is a primary inflammatory cytokine produced by many cells in response to proinflammatory stimuli such as IL-1, TNF, LPS and viruses. Its function is, in part, to attract neutrophils to the site of inflammation and to activate them. The IL-8 cDNA sequence predicts a protein of 99 amino acids. Removal of a 22-residue signal peptide generates a mature protein of 77 amino acids (~ 8 kDa). Further proteolysis of the N-terminal end leads to a variant form with 72 amino acids; full activation of IL-8 may require cleavage to the 72 amino acid form. IL-8 can form non-covalent dimers in solution, especially at high concentrations, but dimerization is not necessary for biological activity.