CD4-CD8 - T cell receptor αβ T cells: Generation of an in vitro major histocompatability complex class I specific cytotoxic T lymphocyte response and allogeneic tumor rejection

The generation of an in vitro major histocompatibility complex class I specific response of CD4⁻CD8⁻ T cell receptor (TCR) αβ cytotoxic T lymphocytes (CTL) and their allogeneic tumor rejection were investigated. Inocula ofBALBRLo’ 1 were rejected in C57BL/6 (B6) mice treated with minimum essential medium (MEM) (control), anti-L3T4 (CD4) monoclonal antibody (mAb) or anti-Lyt-2.2 (CD8) mAb and CTL against the tumor were generated in vitro. No rejection and no induction of CTL were observed in B6 mice treated with anti-L3T4 (CD4) plus anti-Lyt-2.2 (CD8) mAb. CTL with the classical Thy-1⁺CD3⁺CD4⁻ CD8⁺ TCR αβ phenotype were generated in mixed lymphocyte tumor cell culture (MLTC) spleen cells from B6 mice treated with MEM (control) or anti-L3T4 (CD4) mAb, whereas CTL with an unusual Thy-1⁺CD3⁺CD4⁻ CD8⁻ TCR αβ phenotype were generated in MLTC spleen cells from anti-Lyt-2.2 (CD8) mAb-treated B6 mice. Both types of CTL were reactive with both H-2K^d and D^d (L^d) class I antigen. These findings suggest that when CD4⁺ cells were blocked by anti- L3T4 (CD4) mAb, CD8⁺ CTL mediated rejection, and when CD8⁺ cells were blocked by anti-Lyt-2.2 (CD8) mAb, CD4⁺ cells were capable of mediating rejection, although less efficiently than CD8⁺ cells, by inducing CD4⁻ CD8⁻ TCR αβ CTL. The finding that adoptive transfer of CD4 and CD8-depleted MLTC spleen cells, obtained from anti-Lyt-2.2 (CD8) mAbtreated B6 mice that had rejected BALBRLa 1, resulted in rejection of BALBRLa 1 inoculated into B6 nu/nu mice confirmed the above notion. CTL clones with the CD4⁻ CD8⁻ TCR αβ phenotype specific for L^d were established.