Histocompatibility 2, class II antigen A, alpha (H2-Aa) (H2-Aa)

Histocompatibility 2, class II antigen A, alpha (H2-Aa) is a protein-coding gene in mice that encodes the alpha chain of the I-A molecule, a member of the major histocompatibility complex (MHC) class II family (UniProt P04224). It is primarily expressed on the surface of professional antigen-presenting cells, such as dendritic cells, B cells, and macrophages, where it forms a heterodimer with the H2-Ab1 beta chain (NCBI Gene 14960). The primary biological function of H2-Aa is to bind and present processed exogenous peptides to the T-cell receptors (TCR) of CD4+ T helper cells, a process fundamental to the initiation of the adaptive immune response. In disease contexts, H2-Aa is heavily involved in the pathogenesis of autoimmune disorders, where the presentation of self-peptides can trigger aberrant immune attacks (PubMed: 25607456). It also plays a critical role in the immune system's ability to recognize and respond to infectious pathogens and tumor-associated antigens. While H2-Aa itself is often a target of research-grade monoclonal antibodies like M5/114.15.2 to study immune modulation, its human orthologs (HLA-DQ) are significant targets for developing therapies for allergies and transplant rejection. Understanding the structural and functional nuances of H2-Aa is essential for the design of vaccines and immunotherapies that aim to either enhance or suppress specific immune pathways.

Other names

I-A alphaMHC class II antigen A alphaH-2 class II antigen A alphaIAaH2-IAAI323765

Presentation of exogenous peptides to CD4+ T-cell receptors to initiate adaptive immune responses.