Differential Tumor Immunogenicity of DBA/2 Mouse Lymphoma L1210 and Its Sublines. II. Increased Expression of Tumor-Associated Antigens on Subline Cells Recognized by Serologic and Transplantation Methods2

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Abstract
The expression of surface antigens and the immunogenicity of DBA/2 mouse lymphoma L1210 and three L1210 sublines were investigated. Each subline was resistant to a different antileukemic agent, i.e., guanazol, methylglyoxal-bis-guanylhydrazone, and 4,4-diacetyldiphenyl-urea-bis-guanylhydrazone. Although syngeneic primary immunization of DBA/2 mice with the irradiated parental L1210 had not shown any serum antibody response against the parental L1210 nor against any of the sublines, we have now found that syngeneic hyperimmune antisera, which were raised against the parental L1210, reacted weakly with the parental L1210 cells. However, this antiserum as well as syngeneic hyperimmune antisera raised against the L1210/GZL subline reacted strongly with cells of all sublines tested. The syngeneic hyperimmune antisera reacted weakly with the parental cells. These results were obtained by complement-dependent cytotoxicity tests and membrane immunofluorescence. Quantitative absorption of anti-parent antisera and anti-subline antisera with tumor cells revealed that, although either subline cells or the parental cells removed the antibody activity of both antisera completely, subline cells were more efficient. Normal spleen cells did not remove the activity. However, parental and subline tumor cells were not markedly different in their susceptibilities to anti-H-2K or D cytotoxic activities or in their capacities to absorb the activities of alloantisera. Findings showed that the expression of common tumor-associated antigens was selectively greater on subline cells than on parent line cells, as detected by serologic methods. Tumor transplantation studies on syngeneic immunized animals demonstrated high immunogenicity of subline cells as compared to the lower immunogenicity of parent cells, and sharing of common transplantation antigens by all sublines as well as by the parental line. No evidence was obtained for relationship of the tumor-associated antigen with known murine leukemia virus-related antigens.