Cell surface antigens of a mouse testicular teratoma. Identification of an antigen physically associated with H-2 antigens on tumor cells.

Rabbit antisera to a mouse testicular teratoma, absorbed with normal mouse tissues, react by immunofluorescence with plasma membrane antigens of a variety of transplantable mouse tumor cells and transformed fibroblast cell lines including Clone 1D, SV-40-3T3, and 3T12. Trypsin treatment of cells of "normal" lines, 3T3 and FR-SV-3T3, uncovers reactivity on these as well. Early passage mouse embryo fibroblast cell cultures do not react even after trypsinization. By cross-absorbtion studies, the anti-teratoma serum appears to react with an antigen common to most tumor cells investigated thus far. When this antigen on Clone 1D cells is "capped," H-2 antigens collect with the teratoma antigens in the cap indicating a physical association between the molecules. Molecules specified by both the H-2D and H-2K regions are bound to the teratoma antigens in the Clone 1D plasma membrane. This antigen is also found in soluble tumor cell fractions where it is believed to be free of H-2. A second cell surface antigen defined by anti-teratoma serum is expressed only by hepatoma and teratoma itself. This second antigen is apparently a secretory product of teratoma cells. A third surface antigen defined by anti-teratoma serum appears to be specific for the teratoma.