MICB (MHC Class I Polypeptide-Related Sequence B) is a gene that encodes a stress-induced protein involved in immune system activation. It acts as a ligand for the NKG2D receptor on natural killer (NK) cells and certain T cells, assisting the immune system in identifying and responding to infected or transformed cells. MICB expression rises under cellular stress conditions, such as viral infections or tumor formation, enhancing immune surveillance and targeted destruction of affected cells.