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

MICB is a highly polymorphic cell-surface glycoprotein of the MHC class I-related protein family, encoded within the human MHC locus. Unlike classical MHC class I molecules, MICB does not present peptides; rather, it is upregulated under cellular stress (infection, transformation, DNA damage) and functions as a ligand for the activating immunoreceptor NKG2D, stimulating the cytolytic activity of NK cells and CD8+ T cells. MICB is minimally expressed by healthy cells, largely intracellular, but is upregulated and sometimes shed from the cell surface in tumors or damaged tissues. This serves as an alert signal for immune elimination of potentially dangerous cells but is also exploited by tumors as a mechanism for immune escape via proteolytic shedding or exosome release. MICB expression is regulated by multiple post-transcriptional modifications and is a focus for experimental cancer immunotherapy, although direct targeting strategies remain in research.

Other names

MHC class I chain-related protein BMICA/B (when discussed together with MICA)MICB

Activation of immune response via NKG2D binding Potential immune modulation or checkpoint inhibition through antibody-based therapies targeting MICB/MICA