Cell Surface Antigens of Radiation Leukemia Virus‐induced BALB/c Leukemias Defined by Syngeneic Cytotoxic T Lymphocytes

Two cell surface antigens of mouse leukemias were defined by BALB/c cytotoxic T lymphocytes (CTL) generated against syngeneic radiation leukemia virus(RadLV)‐induced leukemia, BALBRV1 or BALBRVD. Hyperimmunization of BALB/c mice with irradiated leukemias followed by in vitro sensitization of primed spleen cells resulted in the generation of CTL with high killing activity. The specificity of CTL was examined by direct cytotoxicity assays and competitive inhibition assays. A shared cell surface antigen, designated as BALBRV1 antigen, was detected by BALB/c anti‐BALBRV1 CTL. BALBRV1 antigen was expressed not only on RadLV‐induced BALB/c leukemias except for BALBRVD, but also on spontaneous or X‐ray‐induced BALB/c leukemias, chemically‐induced leukemias with the H‐2(d) haplotype and some chemically‐induced BALB/c sarcomas. In contrast, a unique cell surface antigen, designated as BALBRVD antigen, was detected by BALB/c anti‐BALBRVD CTL. BALBRVD antigen was expressed only on BALBRVD, but not on thirty‐nine normal lymphoid or tumor cells. These two antigens could be distinguished from those previously defined on Friend, Moloney, Rauscher or Gross murine leukemia virus (MuLV) leukemias, or MuLV‐related antigens. Both cytotoxic responses were blocked by antisera against H‐2K(d), but not H‐2D(d). The relationship of BALBRV1 antigen and BALBRVD antigen to endogenous MuLV is discussed with regard to the antigenic distribution on tumor cell lines.