HLA-DM, HLA-DO and tapasin: functional similarities and differences

Curr Opin Immunol. 2002 Feb;14(1):22-9. doi: 10.1016/s0952-7915(01)00294-1.


In both the MHC class II and class I pathways of antigen presentation, accessory molecules influence formation of MHC-peptide complexes. In the MHC class II pathway, DM functions in the loading and editing of peptides; recent work demonstrated that it is acting not only in late endosomal compartments but also in recycling compartments and on the surface of B cells and immature dendritic cells. DM activity is modulated by another accessory molecule, DO, but this modulation is mainly operative in B cells, where it may lead to preferential activation of B cells producing high-affinity antibodies. In the MHC class I pathway of antigen presentation, recent in vivo experiments with knockout mice confirmed the role of tapasin in antigen presentation and indicate that it acts as a peptide editor and as a chaperone for TAP and the MHC class I heavy chain. In the class I loading complex, calreticulin and the thiol-dependent oxidoreductase ER60/ERp57 appear to support the function of tapasin in an as-yet-unknown fashion. The picture emerges that DM and tapasin have analogous functions in shaping the peptide repertoire presented by the respective MHC class II and class I molecules.

Publication types

  • Comparative Study
  • Review

MeSH terms

  • Animals
  • Antigen Presentation*
  • Antiporters / immunology*
  • HLA-D Antigens / immunology*
  • Histocompatibility Antigens Class I / immunology
  • Histocompatibility Antigens Class II / immunology
  • Humans
  • Immunoglobulins / immunology*
  • Membrane Transport Proteins
  • Mice
  • Mice, Knockout


  • Antiporters
  • HLA-D Antigens
  • HLA-DM antigens
  • HLA-DO antigens
  • Histocompatibility Antigens Class I
  • Histocompatibility Antigens Class II
  • Immunoglobulins
  • Membrane Transport Proteins
  • tapasin