The TRA-1-81 monoclonal antibody reacts with a pluripotent-stem-cellspecific antigen expressed upon the surface of human embryonic stem (ES) cells, embryonal carcinoma (EC) cells, and embryonic germ (EG) cells. The expression of TRA-1-81 antigen is stage-specific and can be used to characterize embryonic cells and monitor their differentiation. As human EC and ES cells undergo differentiation, expression of TRA-1-81 antigen is lost. TRA-1-81 antibody recognizes a carbohydrate epitope expressed on podocalyxin, a sialoglycoprotein structurally related to CD34. Podocalyxin is a transmembrane glycoprotein which has been implicated in the development of aggressiveness in a variety of cancers, including breast and prostate cancer.
