STUDIES OF TARGET CELL RECOGNITION BY CYTOTOXIC T LYMPHOCYTES
CHAPDELAINE, JOAN MARY
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Cytotoxic T lymphocytes (CTL) generated during a murine sarcoma virus (MSV) infection have been found to be specific for both viral and H-2 antigens. Thus, in order for a target cell to be killed, it must express the same H-2 antigens as the CTL (H-2 restriction). Specifically, CTL recovered from primary MSV-induced tumors and spleens of H-2('b) mice are specific for the H-2D('b) molecule recognized in association with a viral antigen shared by the Friend, Moloney and Rauscher (FMR) viruses. The MSV-induced tumors also contain primed CTL precursor cells which, when restimulated in vitro, have the same specificity as the active cytotoxic T cells.;The H-2D('b) specificity has now been studied using a mutant cell line. A Friend virus-induced tumor cell line originating from a heterozygous H-2('b)/H-2('d) mouse was mutagenized with ethyl methanesulfonate (EMS). These cells were then treated with a hybridoma antibody directed against the H-2D('b) molecule in the present of rabbit complement. The surviving cells were no longer susceptible to the hybridoma antibody but were still lysed with conventional anti-H-2D('b) alloantiserum plus complement. Data obtained by sequential immunoprecipitation followed by gel electrophoresis indicate that both antisera recognized the same molecule. When the mutant cells were used as targets for H-2D('b)FMR specific CTL, the amount of cell lysis, compared to that seen with the nonmutant parent cells, was drastically decreased. However, they remain susceptible to allogeneic CTL raised against the H-2D('b) molecule. The mutant cells also did not differ from the parent cells in their level of viral antigen expression. Comparative tryptic peptide maps indicated that the H-2D('b) molecules from the parental and mutant cells were similar but not identical.;These studies suggest that a possible mechanism of escape by virus-infected cells from destuction by CTL might be alteration by somatic mutation of the Class I H-2 glycoprotein(s) that must be recognized by the CTL in order for them to be effective.