CD4+ T cells can acquire cytotoxic features under inflammatory and tumor conditions, including the secretion of granzymes, perforin, and IFN-γ, as well as the surface expression of killer ligands such as CRTAM, FasL, NKG2D, and TRAIL (CD253), which induce apoptosis in target cells [15, 16]. Here, KLRK1 is linked to neoplasm.