CXCL16, also known as SR-PSOX (scavenger receptor for phosphatidylserine and oxidized lipoprotein), binds to CXCR6/Bonzo/ STRL33, induces a strong chemotactic response and induces calcium mobilization. CXCL16, an alpha (CXC) chemokine, also has characteristics of CC chemokines and a structure similar to fractalkine (neurotactin) in having a transmembrane region and a chemokine domain suspended by a mucin-like stalk. Northern blot analysis of mouse and human tissues detect a 2.2-kb CXCL16 transcript in spleen, lymph nodes, Peyer patches, lung, kidney, small intestine, and thymus, with weak expression in heart and liver and no expression in brain and bone marrow. Flow cytometry and Western blot analysis demonstrate expression of a glycosylated cell-surface protein and a cell supernatant soluble protein.