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

Hum Immunol. 2013 Oct;74(10):1280-7. doi: 10.1016/j.humimm.2013.05.010. Epub 2013 Jun 10.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Bacterial / immunology*
  • Antigens, Bacterial / metabolism*
  • Antigens, Differentiation, B-Lymphocyte / immunology*
  • Antigens, Differentiation, B-Lymphocyte / metabolism
  • B-Lymphocytes / immunology
  • B-Lymphocytes / metabolism
  • Bacterial Toxins / immunology
  • Bacterial Toxins / metabolism
  • Cell Line
  • Enterotoxins / immunology
  • Enterotoxins / metabolism
  • Gene Expression
  • Gene Knockout Techniques
  • HLA-D Antigens / chemistry
  • HLA-D Antigens / genetics
  • HLA-D Antigens / immunology*
  • HLA-D Antigens / metabolism*
  • Histocompatibility Antigens Class II / chemistry
  • Histocompatibility Antigens Class II / immunology*
  • Histocompatibility Antigens Class II / metabolism
  • Humans
  • Mice
  • Protein Binding / immunology
  • Superantigens / immunology*
  • Superantigens / metabolism*

Substances

  • Antigens, Bacterial
  • Antigens, Differentiation, B-Lymphocyte
  • Bacterial Toxins
  • Enterotoxins
  • H-2O antigen
  • HLA-D Antigens
  • HLA-DM antigens
  • HLA-DO antigens
  • Histocompatibility Antigens Class II
  • Superantigens
  • enterotoxin F, Staphylococcal
  • invariant chain
  • enterotoxin A, Staphylococcal