MHC Class II Antigen Processing and Presentation

Major histocompatibility complex class II (MHC II) molecules are central to adaptive immunity, presenting peptides derived from extracellular proteins to CD4+ T helper cells. Biosynthesis begins in the endoplasmic reticulum, where MHC II α and β chains associate with the invariant chain (Ii). This chaperone blocks premature peptide binding and directs the complex to endosomal compartments, where proteases such as cathepsins degrade Ii into the class II–associated invariant chain peptide (CLIP). HLA-DM then catalyses the release of CLIP and edits the peptide repertoire by favouring stable peptide–MHC II complexes. The resulting peptide–MHC II complexes traffic to the cell surface of professional antigen-presenting cells and are interrogated by T cell receptors, initiating immune responses. Allelic polymorphism and conformational dynamics of MHC II shape the spectrum of presented peptides, influencing susceptibility to infection, autoimmunity and informing vaccine or immunotherapy design.

Research from Nature Portfolio

Recent studies have elucidated the intrinsic dynamic features of MHC II that underpin peptide exchange. One investigation of multiple HLA-DRB1 allotypes demonstrated that, despite differences in thermodynamic stability, allotypes maintain a conserved conformation susceptible to HLA-DM editing. This work linked dynamic allosteric coupling in MHC II to peptide exchange rates and proposed mechanisms by which certain allotypes contribute to autoimmune predisposition. Complementing this, molecular dynamics simulations combined with NMR-detected hydrogen/deuterium exchange have revealed that peptide–MHC II complexes sample rare intermediate conformations. These intermediates correlate with both intrinsic and HLA-DM-catalysed exchange pathways, offering a unified model of how allelic variation and conformational flexibility govern epitope selection.

Research from all publishers

High-resolution structural analysis using cryo-electron microscopy has provided atomic models of full-length HLA-DR and HLA-DQ in complex with invariant chain, clarifying interactions among transmembrane domains, loop regions and CLIP. This work completes the structural trajectory from biosynthesis to peptide loading intermediates and informs on the assembly of class II–Ii trimers. In a complementary in vitro approach, a cell-free antigen processing system reconstituting HLA-DR1, HLA-DM and key proteases identified over thirty novel HIV-1 epitopes, revealing how protein stability and solvent accessibility determine epitope selection and guiding vaccine design strategies. Finally, studies of H2-O (the murine analogue of HLA-DO) deficiency have shown that loss of this peptide-editing chaperone skews thymic selection towards regulatory T cells and drives peripheral CD4+ T cell hyperactivity, offering fresh insights into mechanisms of autoimmunity and potential therapeutic targets.

MHC Class II Antigen Processing and Presentation publication trend

The graph below shows the total number of articles in mhc class ii antigen processing and presentation across all publications each year (not limited to Nature Index journals).

Technical terms

MHC class II: Cell-surface glycoproteins that bind and present extracellularly derived peptides to CD4+ T helper cells.

Invariant chain (Ii): A chaperone that associates with MHC II in the endoplasmic reticulum, preventing premature peptide loading and targeting complexes to endosomes.

CLIP: The class II–associated invariant chain peptide that occupies the MHC II peptide-binding groove until peptide editing occurs.

HLA-DM: A nonclassical MHC II molecule that catalyses the release of CLIP and edits the peptide repertoire by promoting stable peptide–MHC II complexes.

HLA-DO (H2-O): A modulator of HLA-DM activity, influencing the diversity and selection of peptides loaded onto MHC II molecules.

References

1. MHC-II dynamics are maintained in HLA-DR allotypes to ensure catalyzed peptide exchange. Nature Chemical Biology (2023).
2. MHC class II complexes sample intermediate states along the peptide exchange pathway. Nature Communications (2016).
3. Structural insights into human MHC-II association with invariant chain. Proceedings of the National Academy of Sciences of the United States of America (2024).
4. A cell-free antigen processing system informs HIV-1 epitope selection and vaccine design. Journal of Experimental Medicine (2023).
5. H2-O deficiency promotes regulatory T cell differentiation and CD4 T cell hyperactivity. Frontiers in Immunology (2024).