GCP-2 (granulocyte chemotactic protein-2) also known as CXCL6, is a CXC chemokine initially isolated as a neutrophil chemoattractant from the MG-63 osteosarcoma cell line. Among human CXC chemokines, GCP-2 is most closely related to ENA-78 (78% amino acid (aa) sequence identity in the mature peptide region and 86% identity in the signal sequence). The structure and sequence of the genes for human GCP-2 and ENA-78 also exhibit close similarity suggesting the two genes may have originated from a gene duplication. LIX (LPS-induced CXC chemokine) was initially cloned as a gene induced by LPS in mouse fibroblasts. The predicted LIX protein sequence is identical to a previously purified mouse protein designated mouse GCP-2 based on its amino sequence similarity (60% sequence identity) to human GCP-2. Mouse GCP-2/LIX is also 54% identical with human ENA-78 at the amino acid sequence level.