Anti-Human HLA-DR (MHC Class II) - Purified

HLA-DR antibody, clone L243, recognizes the major histocompatibility complex (MHC) class II molecule Human Leukocyte Antigen - DR isotype (HLA-DR). MHC class II is constitutively expressed on human professional antigen-presenting cells (APCs), including macrophages/monocytes, dendritic cells (DCs), and B cells, and is induced on T cells upon activation2. HLA-DR consists of two transmembrane proteins, a 35 kDa α (heavy) chain and 29 kDa β (light) chain3 encoded by the HLA-DRA and HLA-DRB1, HLA-DRB3, HLA-DRB4, and HLA-DRB5 genes, respectively, located in the HLA complex of chromosome 6. The N-terminal α1 and β1 domains form the antigen-binding groove, which binds 13-25 aa peptides derived from exogenous antigens4. On APCs, MHC class II plays a critical role in the adaptive immune response by presenting phagocytosed antigens to helper CD4 T cells. The T cell receptor (TCR)/CD3 complex of CD4 T cells interacts with peptide-MHC class II, which induces CD4 T cell activation leading to the coordination and regulation of other effector cells. CD4 molecules also bind to MHC class II, which helps augment TCR signaling5. It has also been demonstrated that MHC class II express on activated T cells are capable of antigen presentation6 and can transduce signals into T cells, enhancing T cell proliferation and activity7. HLA-DR expression is a marker of T cell activation and correlates with disease activity in patients with autoimmune disease8 and rapid progression in HIV infection9. Specific alleles of HLA-DR are associated with autoimmune diseases, including rheumatoid arthritis10.