Major histocompatibility complex class II (MHC II) presenting Hepatitis B surface antigen (HBsAg) peptides (MHC II-HBsAg)

The Major Histocompatibility Complex class II (MHC II) molecule presenting Hepatitis B surface antigen (HBsAg) peptides is a fundamental immunological assembly required for the clearance of Hepatitis B virus (HBV) infection. This complex is formed on the surface of professional antigen-presenting cells (APCs) after the internalization and proteolytic processing of HBsAg into 13-25 amino acid peptides, which are then loaded onto MHC II molecules like HLA-DR [NIH: StatPearls]. Recognition of this complex by the T-cell receptor (TCR) of naive or memory CD4+ T cells is the primary signal for helper T-cell activation, which is essential for orchestrating both the humoral (antibody) and cellular arms of the immune system [PubMed: 30104468]. In chronic HBV infection, the presentation of HBsAg via MHC II is often insufficient or leads to T-cell exhaustion, preventing viral clearance. Therapeutic interventions, such as recombinant vaccines and novel T-cell-directed immunotherapies, target this pathway to induce or restore robust HBsAg-specific CD4+ T-cell responses [PubMed: 25605863]. Monitoring the efficacy of these interventions often involves measuring anti-HBs antibody titers and the frequency of HBsAg-specific T cells.

Other names

HLA-DR-HBsAg complexMHC II-HBsAg peptide complexHBsAg-MHC II complexHLA-DQ-HBsAg complexHLA-DP-HBsAg complex

The complex presents processed HBsAg epitopes to the T-cell receptors (TCR) of CD4+ T cells, initiating an adaptive immune response characterized by cytokine release and B-cell activation for antibody production [PubMed: 25605863].