Another NK cell receptor, NKG2D, though not required for mediating ADCC, is critical for NK cell activation after binding to its ligands, major histocompatibility complex (MHC) class I-related chain A and B (MICA and MICB/MICAL-1 and MICAL-2), which are overexpressed on tumor cells. The gene discussed is MICA; the disease is neoplasm.