Cytotoxic T lymphocytes recognize determinants on the BALB/c-H-2L^d molecule controlled by α1 and α2 but not α3 external domains

We have shown that cytotoxic T lymphocytes (CTL) raised in H-2^dmice use H-2L^d but not H-2D^d or H-2K^d antigens as restricting elements in lymphocytic choriomeningitis virus (LCMV) and vesicular stomatis virus (VSV) infections. To localize the regions of H-2L^d protein recognized by CTL, we constructed a recombinant H-2L^d/D^dgene encoding a hybrid antigen with α1 and α2 external domains of H-2L^d and α3, transmembrane and cytoplasmic domains of H-2D^d. The recombinant gene was transfected into mouse cells and the hybrid molecules were characterized serologically, biochemically and functionally. In all assays, H-2L^d/D^d molecules were recognized by LCMV- and VSV-specific H-2L^d-restricted CTL in a manner similar to that of wild-type H-2L^d antigens. Analogous results were obtained with alloreactive CTL. Hybrid antigens containing the α3 domain of H-2L^d fused to α1 and α2 domains of a Qa-2,3 region-encoded antigen were not used as restricting elements by LCMV-specific CTL. These results suggest that H-2L^d-restricted CTL directed against LCMV and VSV recognize determinants controlled by the α1 and/or α2 domains of the H-2L^d molecule.