Human leukocyte antigen DR (HLA-DR) (HLA-DR)

Human leukocyte antigen DR (HLA-DR) is a major histocompatibility complex (MHC) class II cell surface receptor primarily expressed on professional antigen-presenting cells (APCs) such as B cells, dendritic cells, and macrophages (UniProt P01903). Its fundamental biological role is to present processed exogenous peptides to CD4+ T-helper cells, a process essential for the initiation and regulation of the adaptive immune response (PubMed: 10508212). HLA-DR is a heterodimeric glycoprotein consisting of an alpha chain (DRA) and a highly polymorphic beta chain (DRB), the latter of which determines the specificity of peptide binding and is linked to various autoimmune susceptibilities. In oncology, HLA-DR is a significant therapeutic target for monoclonal antibodies in B-cell malignancies, such as non-Hodgkin lymphoma and chronic lymphocytic leukemia, due to its high and stable expression on tumor cells (PubMed: 11560776). Furthermore, the expression levels of HLA-DR on monocytes (mHLA-DR) serve as a critical clinical biomarker for monitoring immune competence; low expression is often indicative of immunoparalysis in patients with sepsis or major trauma, correlating with an increased risk of secondary infections (PubMed: 16447171).

Other names

HLA class IIMHC class II DRHuman leukocyte antigen DR antigenMajor histocompatibility complex class II DRHLA-DRB1HLA-DRA

Monoclonal antibodies targeting HLA-DR bind to the extracellular domain of the receptor on the surface of antigen-presenting cells, particularly malignant B cells. This binding triggers cell death through multiple pathways, including antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and the direct induction of caspase-independent apoptosis. In the context of autoimmune disorders, therapeutic modulation aims to block the presentation of self-antigens to CD4+ T cells, thereby reducing aberrant immune activation.