Human leukocyte antigen DR receptor (HLA-DR)

Human leukocyte antigen DR receptor (HLA-DR) is a heterodimeric cell surface glycoprotein belonging to the major histocompatibility complex (MHC) class II family[1][5][8][9]. It is composed of an alpha and beta chain, both transmembrane proteins, encoded at the HLA-DRA and HLA-DRB loci respectively. HLA-DR molecules are primarily expressed on professional antigen-presenting cells, including B lymphocytes, dendritic cells, and macrophages, where they present exogenous peptide antigens (typically 9–30 amino acids) in a groove formed by the alpha and beta chains[1][9]. The resulting HLA-DR–peptide complex binds to T-cell receptors on CD4^+ helper T cells, initiating or modulating adaptive immune responses[1][5]. HLA-DR polymorphism (mainly in the beta chain) underlies individual differences in immune reactivity, disease susceptibility (particularly autoimmunity), and the success of organ transplantation. Increased or altered HLA-DR expression is also a biomarker for immune activation, sepsis, and various inflammatory or malignant states. Drugs or biologics may modulate HLA-DR–related pathways to dampen or redirect immune responses in autoimmune diseases, transplant rejection, and cancer immunotherapy[1][3][7][8][9].

Other names

HLA-DR moleculeHLA-DR antigenHLA-DR receptorMajor histocompatibility complex class II DRMHC class II DR

Inhibition of T-cell activation by interfering with antigen presentation Immunosuppression (blocking signal pathways downstream of HLA-DR:T-cell receptor engagement) Depletion or modulation of antigen-presenting cells expressing HLA-DR