NKG2D defines tumor‐reacting effector CD8(+) T cells within tumor microenvironment

For successful immunotherapy for cancer, it is important to understand the immunological status of tumor antigen‐specific CD8(+) T cells in the tumor microenvironment during tumor progression. In this study, we monitored the behavior of B16OVA‐Luc cells in mice immunized with a model tumor antigen ovalbumin (OVA). Using bioluminescence imaging, we identified the time series of OVA‐specific CD8(+) T‐cell responses during tumor progression: initial progression, immune control, and the escape phase. As a result of analyzing the status of tumor antigen‐specific CD8(+) cells in those 3 different phases, we found that the expression of NKG2D defines tumor‐reacting effector CD8(+) T cells. NKG2D may control the fate and TOX expression of tumor‐reacting CD8(+) T cells, considering that NKG2D blockade in OVA‐vaccinated mice delayed the growth of the B16OVA‐Luc2 tumor and increased the presence of tumor‐infiltrating OVA‐specific CD8(+) T cells.