TRA-1-60-R antibody recognizes the neuraminidase resistant form of TRA-1-60. TRA-1-60 is a 200-240 kD cell surface antigen expressed by human embryonic stem cells (ESC), embryonic germ cells (EG), and embryonal carcinoma cells. The expression of TRA-1-60 on human ESC is downregulated upon differentiation. The soluble form of TRA-1-60 has been found in the serum of patients with embryonic cancers. Historically, TRA-1-60 is a neuroaminidase-sensitive (TRA-1-60-S) carbohydrate epitope expressed on podocalyxin, a member of the mucin-like glycoprotein CD34 family. Podocalyxin is a type I transmembrane sialoprotein with anti-adhesion properties. Further studies have shown that some of TRA-1-60 is neuraminidase resistant (TRA-1-60-R). The two forms of TRA-1-60 are essentially indistinguishable in terms of their cellular reactivity except for the difference in neuraminidase sensitivity. Both of TRA-1-60-S and TRA-1-60-R appear to be the same molecular weight glycoproteins detected by Western blot.