CXCL16 is a member of the CXC chemokine family and signals through the CXCR6 receptor. CXCL16 may play a role in attracting lymphocyte subsets during inflammation and may facilitate certain immune responses. The chemokine domain of CXCL16 contains six cysteine residues including the four highly conserved cysteine residues characteristic of CXC chemokines. The CXCL16 gene codes for a 273 amino acid polypeptide, which includes a 29 amino acid cytoplasmic domain and transmembrane sequence containing approximately 20 amino acids. The extracellular portion of CXCL16 contains a chemokines domain and an extended C-terminal ``mucin-like stalk'' sequence. The extracellular domain contains 89 amino acid residues (86 a.a. residues for the murine homolog