Human leukocyte antigen class II–peptide complex (HLA-II–peptide complex)

Human leukocyte antigen (HLA) class II–peptide complexes are heterodimeric surface proteins primarily expressed on professional antigen-presenting cells, such as dendritic cells, macrophages, and B cells. These complexes play a pivotal role in the adaptive immune system by binding exogenous peptides—derived from the proteolytic degradation of extracellular proteins—and presenting them to the T-cell receptors (TCRs) of CD4+ helper T cells (Roche & Furuta, 2015). This interaction is fundamental for the initiation of immune responses against pathogens and the maintenance of self-tolerance (Neefjes et al., 2011). Dysregulation or specific genetic variants of HLA class II molecules are strongly linked to the pathogenesis of numerous autoimmune diseases, including rheumatoid arthritis, type 1 diabetes, and celiac disease, where they present self-peptides or dietary antigens to autoreactive T cells (Jones et al., 2006). In oncology, HLA class II–peptide complexes are increasingly targeted by immunotherapies, such as TCR-engineered T cells and peptide vaccines, to direct the immune system against tumor-specific neoantigens (Hailemichael et al., 2013). Therapeutic interventions include the use of competitive peptide binders to block autoimmune presentation or the development of biologics that specifically recognize tumor-associated pMHCII complexes (Schooten et al., 2022).

Other names

MHC class II–peptide complexpMHCIIHLA-DR–peptide complexHLA-DQ–peptide complexHLA-DP–peptide complexMajor histocompatibility complex class II–peptide complex

Drugs targeting HLA class II–peptide complexes typically act by competing for the peptide-binding groove to prevent the presentation of pathogenic self-antigens, or by serving as the target for engineered T-cell receptors (TCRs) and antibodies to induce selective immune modulation or cell lysis.