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The role of H2‐O and HLA‐DO in major histocompatibility complex class Il‐restricted antigen processing and presentation
Author(s) -
Alfonso Christopher,
Liljedahl Monika,
Winqvist Ola,
Surh Charles D.,
Peterson Per A.,
FungLeung WaiPing,
Karlsson Lars
Publication year - 1999
Publication title -
immunological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.839
H-Index - 223
eISSN - 1600-065X
pISSN - 0105-2896
DOI - 10.1111/j.1600-065x.1999.tb01370.x
Subject(s) - major histocompatibility complex , human leukocyte antigen , biology , histocompatibility , antigen processing , immunology , antigen presentation , minor histocompatibility antigen , antigen , class (philosophy) , presentation (obstetrics) , genetics , immune system , mhc class i , t cell , medicine , epistemology , philosophy , radiology
Summary: The function of major histocompatibility complex (MHC) class II molecules is to sample exogenous antigens for presentation to CD4 + T helper cells. After synthesis in the endoplasmic reticulum, class II molecules are directed into the endosomal system by association with the invariant chain (Ii), which is sequentially cleaved, generating class II dimers loaded with Ii‐derived peptides (CLIP). These class Il‐peptide complexes are physiological substrates for H2‐M/HLA‐DM, a resident of the endosomal/lysosomal system which facilitates the removal of CLIP from newly synthesised class II αβ dimers. Exchange of CLIP for antigenic class Il‐binding peptides is also promoted by the action of H2‐M/HLA‐DM, resulting in stable peptide‐class II complexes that are transported to the cell surface for presentation to CD4 + T cells. Recent evidence suggests that this H2‐M/HLA‐DM‐mediated ‘peptide editing’ is influenced by another MHC class Il‐encoded molecule, H2‐O/HLA‐DO. This non‐polymorphic αβ heterodimer is associated with H2‐M/HLA‐DM during intra‐cellular transport and within the endosomal system of B cells, H2‐0/HLA‐DO alters the peptide exchange function of H2‐M/HLA‐DM in a pH‐dependent manner, so that H2‐M/HLA‐DM activity is limited to more acidic conditions, corresponding to lysosomal compartments. Indeed, H2‐O/HLA‐DO may serve to limit the presentation of antigens after fluid phase uptake by B cells, while augmenting presentation of antigens internalised via membrane Ig receptors. Such a mechanism may maintain the fidelity of the B‐cell‐CD4 + T‐cell interaction, counteracting self reactivity arising from less stringent lymphocyte activation. Here, data evaluating the role of H2‐O/HLA‐DO shall be reviewed and its putative function discussed.