Identification of a Human T Cell Clone with the Cytotoxic T Lymphocyte and Natural Killer‐like Cytotoxic Function against Autologous Mammary Carcinoma and K562 Line

Pleural exudative lymphocytes (PLED from a 60‐year‐old female patient showed high cytotoxicity against the autologous mammary tumor line, HMC‐2, and NK‐susceptible K562 cells, although PLEL demonstrated only weak cytotoxic potentials against several allogeneic tumor lines. We successfully obtained seven cytotoxic T cell clones from PLEL bulk populations, and assessed the possibility that these lymphocytes are simply natural killer (NK)‐like cells or have the dual cytotoxic activity of cytotoxic T lymphocytes (CTL) and NK‐like cells. These clones, designated as T(cHMC‐2), showed strong cytotoxicity against both HMC‐2 and K562 cells. In contrast, allogeneic human peripheral blood‐derived NK cells could not kill HMC‐2 targets. Furthermore, a blocking study of T(cHMC‐2) cytotoxicity using monoclonal antibodies against CD3, CD8 and human MHC class I products showed that all of these antigen molecules were involved in the cytotoxicity of T(cHMC.2) clone against autologous HMC‐2 cells, indicating MHC class I recognitive cytotoxicity. These data indicate that the T(cHMC‐2) clone may have dual cytotoxicity with CTL‐ and NK‐like activity against autologous HMC‐2 mammary tumor and K562 cells, respectively.