TRA-1-81 recognizes an antigen of similar size detected as by TRA-1-60, GCTM2, K4, and K21, and all these antibodies detect similar but distinct patterns of expression on panels of tumor-derived cell lines. TRA-1-81 and TRA-1-60 epitopes are associated with distinct molecular species. TRA-1-81, TRA-1-60, GCTM2, and K21 antibodies all recognize distinct epitopes formed by modifications of a common keratan sulfate core molecule that is characteristically expressed by human EC cells. TRA-1-81, clone cl.26, likely recognizes the carbohydrate part of the molecule as TRA-1-60 activity is enhanced by neuraminidase.
This antibody is specific for the TRA-1-81 antigen. On western blots, it identifies the target band at ~200-400 kDa. Reactivity has been confirmed with human EC1003.7 and NTERA-2 cell lysates by western blotting, with smooth muscle cells in frozen normal human arterioles and arteries, intestine, lung, skin, and uterus, as well as epithelial cells of the mammary ducts, stomach, small and large intestine tissues by indirect immunofluorescence, and with lysates from 125I surface-labeled 2102Ep cl.2A6 human EC cells by immunoprecipitation.
TRA-1-60 is a cell surface antigen, expressed along with SSEA-3, SSEA-4, and TRA-1-81 in human embryonic stem cells, embryonal carcinoma cells (EC), and induced pluripotent stem cells (iPS). These surface markers are lost during the differentiation process. In contrast, SSEA-1 is absent in undifferentiated human stem cells but is present on the cell surface after retinoic acid-mediated differentiation. The TRA-1-81 antigen is associated with a polydisperse glycoprotein with a molecular weight in excess of 200,000.
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Protein Aliases: Keratan sulfate antigen TRA1-81; TRA180