title: Bone marrow-derived dendritic cells can process bacteria for MHC-I and MHC-II presentation to T cells.
abstract: Dendritic cells can engulf particulate Ags and induce T cell proliferative responses after pulsing with particulate Ag. However, their capacity to process viable Gram-negative bacteria for presentation by MHC-I and MHC-II has not been shown. We therefore characterized the ability of murine bone marrow-derived dendritic cells to process Escherichia coli and Salmonella typhimurium, expressing defined epitopes for presentation by MHC-I and MHC-II molecules. The I-Ak-restricted 46-61 epitope from hen egg white lysozyme (HEL(46-61)) or the Kb-restricted 257-264 epitope from chicken egg OVA (OVA(257-264)) was expressed as fusion proteins in the bacterial cytoplasm as the Crl-HEL and Crl-OVA fusion proteins, respectively. Bacteria expressing Crl-HEL or Crl-OVA, or beads coated with HEL or OVA, were coincubated with murine bone marrow-derived dendritic cells, and Ag processing and presentation were quantitated using T cell hybridomas. The data show that granulocyte-macrophage CSF-stimulated dendritic cells can process live intact Gram-negative bacteria for peptide presentation by MHC-I and MHC-II. Cytochalasin D inhibition studies revealed that processing for both MHC-I and MHC-II presentation required cytoskeletal rearrangements. Processing for MHC-I and MHC-II presentation was inhibited by ammonium chloride, suggesting that acidic compartments were required. Thus, granulocyte-macrophage CSF-stimulated murine bone marrow dendritic cells are capable of processing exogenous particulate Ags, including bacteria with no known mechanism for phagosomal escape, for peptide presentation by both MHC-I and MHC-II. These data suggest that dendritic cells may be important in priming both CD4+ and CD8+ T cells to bacterial Ags.
authors.affiliation: Department of Cell and Molecular Biology, Lund University, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Svensson
authors.forename: B
authors.initials: B
authors.lastname: Stockinger
authors.forename: M J
authors.initials: MJ
authors.lastname: Wick
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology* / Q000378:metabolism; D001854:Bone Marrow Cells; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects; D003713:Dendritic Cells / Q000276:immunology* / Q000382:microbiology / Q000648:ultrastructure; D004926:Escherichia coli / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008854:Microscopy, Electron; D012486:Salmonella typhimurium / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D000643:Ammonium Chloride; D015638:Cytochalasin D