CXCL16 is a small cytokine protein that is expressed as a cell surface bound molecule, as well as a soluble chemokine. CXCL16 is produced by dendritic cells found in the T cell zones of lympoid organs, and by cells found in the red pulp of the spleen. Cells that can bind to CXCL16 include several subsets of T cells, and natural killer T (NKT) cells, and the ligand interacts with the chemokine receptor CXCR6, also referred to as Bonzo.