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

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Abstract
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 PI 16) 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 turn 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.