Invivo Anti-Human pan MHC Class II (HLA II) Recombinant mAb

Major Histocompatibility Complex Class II (MHC Class II) molecules are polymorphic heterodimeric glycoproteins expressed on the cell surface, encoded by the classical class II genes (HLA-DP, HLA-DQ, and HLA-DR) within the human leukocyte antigen (HLA) gene cluster. Each molecule consists of an α chain and a β chain, each containing a membrane-proximal immunoglobulin-like domain and a membrane-distal peptide-binding domain, which together form an open peptide-binding groove. Unlike MHC Class I molecules that present endogenous antigens, MHC Class II molecules are primarily expressed on the surface of professional antigen-presenting cells (such as dendritic cells, macrophages, and B cells). These cells uptake extracellular antigens through endocytosis or phagocytosis. Within the acidic environment of endosomes/lysosomes, the invariant chain (Ii chain) and its proteolytically cleaved remnant, the CLIP fragment, occupy and bind to the peptide-binding groove. Subsequently, under the catalysis of HLA-DM molecules, CLIP is exchanged for exogenous antigen-derived peptides, typically 13–18 amino acids in length, and the processed antigenic peptides are ultimately presented on the cell surface for recognition by the TCRs of CD4+ helper T cells. This antigen presentation process is essential for initiating and regulating adaptive immune responses, particularly promoting antibody production by B cells and activating other immune cells. However, aberrant expression of MHC Class II molecules—such as ectopic expression on non-professional antigen-presenting cells, or high-affinity binding of specific alleles to self-antigenic peptides—can trigger autoimmune diseases, including rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. Furthermore, the high polymorphism of MHC Class II genes also determines individual variations in immune responses to pathogens and vaccines.