CD147 is also known as Basigin (BSG), or extracellular matrix metalloproteinase inducer (EMMPRIN). The human basigin protein contains 269 amino acids that form two heavily glycosylated C2 type immunoglobulin-like domains at the N-terminal extracellular portion. A second form of basigin has also been characterized that contains one additional immunoglobulin-like domain in its extracellular portion. As members of the immunoglobulin superfamily play fundamental roles in intercellular recognition involved in various immunologic phenomena, differentiation, and development, basigin is thought also to play a role in intercellular recognition and regulate several distinct functions, such as spermatogenesis, expression of the monocarboxylate transporter and the responsiveness of lymphocytes. Basigin is a type I integral membrane receptor that has many ligands, including the cyclophilin (CyP) proteins Cyp-A and CyP-B and certain integrins.