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, aiding the immune system in recognising and responding to infected or transformed cells. MICB expression increases under conditions of cellular stress, such as viral infection or tumour development, enhancing immune surveillance and targeted cell destruction.