Major histocompatibility complex class II I-A^b molecule (I-A^b)

The Major histocompatibility complex class II I-A^b molecule is a mouse-specific heterodimeric glycoprotein composed of alpha (Aβ^b) and beta (Aα^b) chains, encoded within the H-2 I region of the mouse MHC, functioning to present antigenic peptides to CD4+ T helper cells on professional antigen-presenting cells like dendritic cells, macrophages, and B cells. Its peptide-binding groove, formed by the α1 and β1 domains, accommodates longer peptides (13-25 amino acids) due to open ends, enabling recognition of extracellular pathogens and initiation of adaptive immune responses. During biosynthesis, it associates with the invariant chain in the endoplasmic reticulum to prevent endogenous peptide binding, followed by transport to endosomal compartments where HLA-DM homologs facilitate exchange for exogenous peptides. I-A^b is highly polymorphic, influencing peptide specificity and T cell selection in the thymus, critical for immune repertoire diversity. In disease, allelic variants like I-A^b contribute to susceptibility in models of autoimmune disorders such as type 1 diabetes and experimental autoimmune encephalomyelitis, and play roles in transplant rejection and pathogen defense. While not directly targeted by approved drugs, its modulation is explored in immunotherapy and vaccine design, posing challenges like broad immunosuppression or loss of immune surveillance.

Other names

MHC class II H-2 I-A^bH2-I-A^bI-A b