The aim of this study is to investigate the levels of NKG2D-expressing CD8+NKT cells in peripheral blood of lung cancer patients, which are remarkably related to clinical significance, and to analyze the correlation between NKG2D-expressing CD8+NKT cells and sMICA levels, and to explore the role of NKG2D and sMICA in immune surveillance. The gene discussed is KLRK1; the disease is lung cancer.