Description: The TRA-1-81 antibody recognizes a protein expressed on undifferentiated human embryonic stem cells (ES), embyronal carcinoma cells (EC), and embryonic germ cells (EG). Like other stem cell specific markers, the epitope recognized by the TRA-1-81 antibody is lost upon cell differentiation. The TRA-1-81 epitope is resistant to neuraminidase digestion, unlike the epitope recognized by the related TRA-1-60 antibody. The TRA-1-81 antibody is known to specifically recognize a carbohydrate epitope on a keratan sulfated glycoprotein recently identified as podocalyxin, a member of the CD34-related family of sialomucins. Podocalyxin is a transmembrane glycoprotein originally identified on epithelial glomerular cells known as podocytes, and the protein has also been implicated in the development of aggressiveness in a variety of cancers, including breast and prostate cancer.