Detection and characterization of 2-E2-specific surface protein in human pluripotent stem cells.

To investigate cell surface antigens on human embryonic stem cells (hESCs), we generated a panel of monoclonal antibodies (MAbs) against undifferentiated hESCs by a decoy immunization strategy. One of the MAbs, MAb 2-E2, specifically bound to human pluripotent stem cells but not to mouse pluripotent stem cells and mouse embryonic fibroblasts. 2-E2 also bound to human differentiated cells, peripheral blood monocytes, and dermal fibroblasts. 2-E2 antigen expression drastically decreased in retinoic acid-induced differentiated hESCs. However, it gradually increased after initial decrease during embryoid body formation of hESCs. 2-E2 recognized approximately 68 and 27 kDa proteins present on the surface of human pluripotent stem cells. The results suggest that 2-E2-specific surface protein is a novel cell surface protein that plays a role in the early differentiation of human pluripotent stem cells.