Unusual stage-specific embryonic antigen (TEC-4) defined by a monoclonal antibody to embryonal carcinoma cells defective in the expression of embryoglycan.

Most developmentally regulated epitopes identified on embryonal carcinoma cells and murine preimplantation embryos are associated with a glycoprotein-bound large glycan called embryoglycan. To prepare monoclonal antibodies recognizing other, less immunogenic stage-specific embryonic epitopes, we used embryoglycan-negative embryonal carcinoma cells P19XT.1.1 as immunogen. One monoclonal antibody prepared by this strategy was found to react specifically with mouse embryonal carcinoma and embryo-derived stem cell lines. The target epitope, TEC-4, was found to be expressed on eggs and two-cell embryos but was undetectable on later stages of mouse embryos and adult mouse tissues. NaDodSO4/PAGE of immunoaffinity-isolated antigen revealed that TEC-4 epitope is associated with glycoproteins of apparent Mr 120,000 and 240,000. The epitope was resistant to oxidation by sodium periodate and to digestion by endoglycosidase F but was sensitive to treatment with protein-denaturing agents and proteases, which suggested that the epitope is located in the protein moiety of the molecule. In the course of retinoic acid-induced differentiation of embryonal carcinoma cells the epitope disappeared before the onset of morphological differentiation. The combined data indicate that TEC-4 is an unusual stage-specific embryonic antigen that may be amenable to direct genetic analysis.