Mouse Anti-Human HLA-DR, DP, DQ Antibody (Tu39)

HLA-DR, DP, and DQ are three classical class II molecules encoded by the MHC class II region on human chromosome 6. They are all heterodimeric membrane glycoproteins composed of a non-covalently associated α chain (approximately 35 kDa) and β chain (approximately 31 kDa), with the antigen-binding groove formed jointly by the α1 and β1 domains. This groove is open at both ends and can accommodate longer peptides of 12 to 28 amino acids. These molecules are primarily expressed on the surface of professional antigen-presenting cells (such as dendritic cells, B cells, and macrophages) and thymic epithelial cells. By presenting exogenously derived antigenic peptides acquired through the endocytic pathway to CD4⁺ helper T cells, they play a central role in the initiation and regulation of adaptive immune responses. Although the three are structurally similar and functionally coordinated, they differ significantly in their immunobiological properties: HLA-DR is the most extensively studied class II isotype, with the highest polymorphism and the greatest immunogenicity in transplant rejection, and its efficient peptide presentation strictly depends on the assistance of the invariant chain (Ii) and HLA-DM; HLA-DQ is particularly notable for its association with various autoimmune diseases—for example, DQ2 and DQ8 are strong risk alleles for celiac disease, and the crystal structures of the DQ8-insulin peptide complex and the DQ2-gluten peptide complex have been solved, although its dependence on Ii and DM is relatively weaker; HLA-DP has unique biochemical characteristics, being able to form SDS-stable dimers in the presence of HLA-DM alone without Ii, and tends to bind a more restricted peptide repertoire, often presenting viral-derived peptides, with its associations with diseases such as hepatitis B, berylliosis, and myasthenia gravis receiving increasing attention. The differential dependence of the three on the chaperones Ii and DM within the same cellular environment suggests that antigen-presenting cells can differentially regulate peptide loading and transport of different class II isotypes by modulating the levels of these accessory molecules, thereby shaping the specificity and intensity of CD4⁺ T cell responses.