TRAF3IP2 and neoplasm: The antitumor activity of CIKs is MHC-unrestricted and mostly mediated by the interaction of CIKs' membrane receptor NKG2D with MHC class I polypeptide-related sequence MICA, MICB or members of the unique long 16-binding protein (ULBP) family (ULBP1, 2 and 3) on tumor cells [57–59].