title: HLA-DO increases bacterial superantigen binding to human MHC molecules by inhibiting dissociation of class II-associated invariant chain peptides.
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.
authors.affiliation: Laboratoire d'Immunologie Moléculaire, Département de Microbiologie et Immunologie, Université de Montréal, H3C 3J7, Canada.
authors.forename: Abdul Mohammad
authors.initials: AM
authors.lastname: Pezeshki
authors.forename: Georges A
authors.initials: GA
authors.lastname: Azar
authors.forename: Walid
authors.initials: W
authors.lastname: Mourad
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Routy
authors.forename: Mohamed-Rachid
authors.initials: MR
authors.lastname: Boulassel
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Denzin
authors.forename: Jacques
authors.initials: J
authors.lastname: Thibodeau
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology* / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D001427:Bacterial Toxins / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D004768:Enterotoxins / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression; D055786:Gene Knockout Techniques; D006681:HLA-D Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D051379:Mice; D011485:Protein Binding / Q000276:immunology; D018089:Superantigens / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D000944:Antigens, Differentiation, B-Lymphocyte; D001427:Bacterial Toxins; D004768:Enterotoxins; C416186:H-2O antigen; D006681:HLA-D Antigens; C084245:HLA-DM antigens; C046148:HLA-DO antigens; D000949:Histocompatibility Antigens Class II; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal; C045084:invariant chain; C026066:enterotoxin A, Staphylococcal