Immunogenic variants obtained by mutagenesis of mouse mastocytoma P815. V. H‐2 associativity of variant‐specific antigens

By in vitro mutagenesis of mastocytoma P815, it is possible to obtain tumor cell variants that are rejected by syngeneic mice (tum-). Most of these variants carry new individual antigens and stimulate a specific cytolytic T cell (CTL) response in mixed leukocyte tumor cell culture (MLTC). The H-2 associativity of this response was examined for six different variants by measuring the inhibition of cell-mediated cytolysis by antibodies directed against products of the K or the D end of the H-2d complex. The lysis was either not inhibited (variants P91 and P116) or inhibited selectively by anti-Kd (variants P21, P32 and P198) or anti-Dd antibodies (variant P35). All these tum- variants expressed Kd and Dd antigens as measured by absorption of H-2 alloantisera. Long-term CTL clones can be obtained that are specific for individual tum- antigens. The pattern of H-2 associativity obtained with MLTC-derived CTL against four tum- variants was verified with CTL clones directed against the specific antigens of these variants. Concordant results were observed in all cases. In addition to CTL clones specific for tum- antigens, it is possible to isolate clones against a P815 tumor-associated antigen found on all P815 tum- variants. For these clones no clear associativity with either Kd or Dd products was found.