10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 3 2012 (July - September) The tetraspanins are a superfamily of four-span membrane proteins that are widely expressed in mammalian cells. Although they have been implicated in important cell processes and some diseases, it has been difficult to characterise their exact functions. Tspan-11 is a recently identified member of the tetraspanin family. Little is known about Tspan-11; however sequence evidence indicates that Tspan-11 most closely resembles tetraspanin CD151. Recently, Tspan-11 GFP transfected CHO cells were used to immunize mice for generation of monoclonal antibodies (mAbs) and found that these mAbs bound to the surface of Tspan-11 GFP transfected CHO cells, indicating that they are able to recognize native forms of the tetraspanin. Surprisingly, one of cancer cell lines tested, the A549 lung adenocarcinoma cell line, was strongly positive for Tspan-11 mAbs, showing both intracellular and plasma membrane staining. Some preliminary investigations have been carried out on normal cells/tissues; these indicate that Tspan-11 is only expressed weakly, if at all on white blood cells, and may be present on epithelial cells in the colon. Taken together, these findings suggest that Tspan-11 has low, or restricted expression, or that the mAbs characterised so far recognize only some forms of the protein. Arunya Jiraviriyakul Tetraspanins, Tetraspanin 11, Tspan-11, CD151 418-426