TCRαβ+Anti-Tumor Cytolytic T Lymphocytes Express NKR-P1 While the Anti-Tumor Activity of TCRγδ+T Lymphocytes Is Not Correlated to NKR-P1 Expression

The CD8αα homodimer as well as the NK cell receptor-protein 1 (NKR-P1) have been implicated to be preferentially expressed by T cells that develop extrathymically. We have earlier shown that intraperitoneal administration of radiated syngeneic W439 lymphoma cells in rat induces tumor-specific cytotoxic T cells (CTL) expressing the TCRαβ receptor as well as the TCRγδ receptor. In the present study we have addressed the expression of CD8αα/αβ and NKR-P1 on these CTL and their correlation to cytotoxicity activity against the W439 tumor. The induced CD8+T cells differentiated to effective cytotoxic cells regardless of the CD8 composition. NKR-P1+T cells expressing CD8 were found in the peritoneal cavity of untreated rats and this cell population was markedly increased upon lymphoma immunization. Both TCRαβ+cells and TCRγδ+cells expressing NKR-P1 showed high cytotoxicity against the tumor. TCRγδ+NKR-P1−cells were also cytotoxic against the tumor, while TCRαβ+NKR-P1−cells showed no cytotoxicity. NKR-P1+T cells (TCRαβ+and TCRγδ+) were not cytotoxic against NK sensitive targets, which contradicts earlier data implicating a correlation between the expression of NKR-P1 and MHC-unrestricted cytotoxicity. In conclusion, TCRαβ+anti-lymphoma CTL express high levels of LFA-1 and NKR-P1, while the TCRγδ+CTL are not dependant on NKR-P1. These results suggest that NKR-P1 has a different function within the TCRαβ+CTL than within the TCRγδ+CTL in the recognition process of these lymphoma cells.