HLA-DO increases bacterial superantigen binding to human MHC molecules by inhibiting dissociation of class II-associated invariant chain peptides

Abdul Mohammad Pezeshki, Georges A. Azar, Walid Mourad, Jean Pierre Routy, Mohamed Rachid Boulassel, Lisa K. Denzin, Jacques Thibodeau

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HLA-DO (H2-O in mice) is an intracellular non-classical MHC class II molecule (MHCII). It forms a stable complex with HLA-DM (H2-M in mice) and shapes the MHC class II-associated peptide repertoire. Here, we tested the impact of HLA-DO and H2-O on the binding of superantigens (SAgs), which has been shown previously to be sensitive to the structural nature of the class II-bound peptides. We found that the binding of staphylococcal enterotoxin (SE) A and B, as well as toxic shock syndrome toxin 1 (TSST-1), was similar on the HLA-DO+ human B cell lines 721.45 and its HLA-DO- counterpart. However, overexpressing HLA-DO in MHC class II+ HeLa cells (HeLa-CIITA-DO) improved binding of SEA and TSST-1. Accordingly, knocking down HLA-DO expression using specific siRNAs decreased SEA and TSST-1 binding. We tested directly the impact of the class II-associated invariant chain peptide (CLIP), which dissociation from MHC class II molecules is inhibited by overexpressed HLA-DO. Loading of synthetic CLIP on HLA-DR+ cells increased SEA and TSST-1 binding. Accordingly, knocking down HLA-DM had a similar effect. In mice, H2-O deficiency had no impact on SAgs binding to isolated splenocytes. Altogether, our results demonstrate that the sensitivity of SAgs to the MHCII-associated peptide has physiological basis and that the effect of HLA-DO on SEA and TSST-1 is mediated through the inhibition of CLIP release.

Original languageEnglish
Pages (from-to)1280-1287
Number of pages8
JournalHuman Immunology
Issue number10
Publication statusPublished - Oct 2013


ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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