title: The route of bacterial uptake by macrophages influences the repertoire of epitopes presented to CD4 T cells.
abstract: We studied MHC class II (MHC-II)-restricted antigen processing of viable Streptococcus pyogenes by murine macrophages for presentation of two CD4 T cell epitopes of the surface M5 protein. We show that presentation of both epitopes was prevented if actin polymerization was inhibited by cytochalasin D, but not if clathrin-dependent receptor-mediated endocytosis was prevented, suggesting uptake of streptococci by phagocytosis or macropinocytosis was required for presentation of the surface M protein. However, treatment of macrophages with amiloride, which selectively blocks membrane ruffling and subsequent macropinocytosis, inhibited the response to one epitope (M5(308-319)), but had no effect on presentation of the other (M5(17-31)). The effect of the inhibitors on uptake of streptococci was analyzed by electron microscopy. Cytochalasin D completely blocked uptake of streptococci, while dimethyl-amiloride only inhibited uptake into spacious compartments. Neither of the inhibitors altered the cell-surface expression of MHC-II and costimulatory molecules analyzed by flow cytometry. The data suggest that distinct epitopes of a protein associated with viable bacteria may be presented optimally following different uptake mechanisms in the same antigen-presenting cells.
authors.affiliation: Department of Rheumatology, University of Newcastle upon Tyne, Newcastle upon Tyne, GB. alexei.delvig@ncl.ac.uk
authors.forename: Alexei
authors.initials: A
authors.lastname: von Delwig
authors.forename: Emma
authors.initials: E
authors.lastname: Bailey
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Gibbs
authors.forename: John H
authors.initials: JH
authors.lastname: Robinson
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D015703:Antigens, CD / Q000378:metabolism; D018122:B7-1 Antigen / Q000378:metabolism; D051940:B7-2 Antigen; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000378:metabolism; D002103:Cadaverine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002460:Cell Line; D015638:Cytochalasin D / Q000494:pharmacology; D000939:Epitopes / Q000235:genetics / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D013297:Streptococcus pyogenes / Q000235:genetics / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D019013:CD40 Antigens; C497965:Cd86 protein, mouse; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D008562:Membrane Glycoproteins; D015638:Cytochalasin D; C039465:5-dimethylamiloride; D000584:Amiloride; C008542:monodansylcadaverine; D002103:Cadaverine