Major histocompatibility complex class I chain-related protein B (MICB)

Major histocompatibility complex class I chain-related protein B (MICB) is a non-classical MHC class I-like glycoprotein encoded on human chromosome 6p21.33 within the MHC region[1][7]. It shares high sequence and structural similarity with MICA but, unlike classical MHC class I molecules, does not present antigenic peptides or associate with β2-microglobulin[1][7]. Instead, MICB is expressed as a ligand induced by cellular stress, infection, or transformation, functioning as a danger signal by binding and activating the NKG2D receptor present on natural killer (NK) cells, γδ T cells, and CD8+ αβ T cells[1][5][7]. This interaction serves as a key trigger for innate immune surveillance and elimination of potentially harmful cells[1][7]. MICB is highly polymorphic, with over 225 identified alleles; expression is normally low or absent on healthy cells but upregulated in many tumor types and stressed cells, and may occur in both membrane-bound and soluble forms due to proteolytic shedding[1][5][6]. MICB's role in immunity makes it a potential therapeutic and biomarker target in cancer, infection, and immune-related pathologies[6][7].

Other names

MHC class I polypeptide-related sequence BMIC-BMHC class I chain-related protein B

Enhancement or inhibition of immune cell activation via NKG2D pathway modulation; Antibody-dependent cellular cytotoxicity (for experimental antibodies)