Identification and Characterization of a Unique Tumor-associated Surface Antigen on LI 210 Leukemia Cells Recognized by Semisyngeneic Antisera1

The tumor-associated surface antigen on 1.1210 leukemia cells was studied by immunofluorescence staining and immunoprecipitation. AntiLi 210 serum was prepared in BALB/c x DBA/2 I, mice by priming with a hybrid of L1210 and human Lesch-Nyhan fibroblast cells and hyperimmunizing with 1.1210 leukemia cells. This hyperimmune serum was able to demonstrate specific surface fluorescence on L1210 cells, while the antiserum did not react with various mouse tumor cell lines, normal lymphoid tissues, or mitogen-activated lymphoid cells. The anti1.12111serum immunoprecipitated a single polypeptide with a molecular weight of 90,000 from '"1-labeled L1210 cells. The expression of this antigen was enhanced by tumor-promoting agent and heat shock treat ment. The biological significance of the LI2Hi-specific cell surface antigen is discussed.