Major Histocompatibility Complex class II (MHC II) (MHC II)

Major Histocompatibility Complex class II (MHC II) molecules are essential cell surface glycoproteins primarily expressed on professional antigen-presenting cells, such as dendritic cells, macrophages, and B cells. Their primary biological role is to bind exogenous peptides and present them to CD4+ T helper cells, a process critical for the initiation and regulation of the adaptive immune response (PMID: 24553156). The concept of 'shared disease-relevant epitopes' refers to specific conserved amino acid sequences, particularly the 'Shared Epitope' (SE) motif (positions 70-74) found in the HLA-DRB1 chain, which is a major genetic risk factor for the development and severity of rheumatoid arthritis (PMID: 20435114). These epitopes influence the selection of self-peptides and the subsequent activation of autoreactive T cells, leading to chronic inflammation and tissue damage. In the context of drug development, MHC II is targeted to modulate aberrant immune responses in autoimmune diseases. For example, glatiramer acetate acts as a decoy by binding to MHC II molecules to prevent the presentation of myelin-derived antigens in multiple sclerosis (PMID: 17352710). Other therapeutic approaches include the use of monoclonal antibodies to block the MHC-TCR interaction or small molecules designed to inhibit the binding of arthritogenic peptides to the shared epitope groove. Because MHC II is central to immune surveillance, therapeutic strategies must balance the inhibition of autoimmunity with the maintenance of protective immunity against pathogens.

Other names

Human Leukocyte Antigen class IIHLA class IIHLA-DRShared EpitopeHLA-DRB1MHC class II antigen-presenting molecule

Competitive inhibition of peptide binding to the MHC II groove, modulation of T-cell receptor signaling, and prevention of autoreactive T-cell activation.