CD226 and neoplasm: NKT cell subset is the core of CIK and primarily exerts anti-tumor activity by three pathways: (1) CIK cells possess polyclonal TCRs that allow them to recognize tumor cells via TCR-MHC interactions; (2) CIK cells express NK cell activating receptors (NKG2D, DNAM-1, and Nkp30) that allow them to recognize tumor cells without MHC limitation; (3) Some CIK cells express FCγRIII CD16, which allows them to recognize specific tumor cell antigens [206].