title: Exogenous peptides presented by transporter associated with antigen processing (TAP)-deficient and TAP-competent cells: intracellular loading and kinetics of presentation.
abstract: This study investigates the differential capacity of TAP-deficient T2 cells, TAP-competent EBV cells, and immature and mature dendritic cells to present peptides to preformed CTL lines. It demonstrates that presentation of exogenous peptides involves peptide uptake and loading onto newly synthesized MHC class I molecules. This mechanism was best demonstrated for low affinity peptides in the presence of irrelevant peptides competing for HLA binding sites. Under these circumstances, inhibition of protein synthesis with cycloheximide or vesicular trafficking with brefeldin A significantly reduced the presentation of low affinity peptides. This was not restored by adding exogenous beta(2)-microglobulin to stabilize the MHC complex on the cell surface. In contrast, presentation of high affinity peptides was not sensitive to cycloheximide or brefeldin A, which suggests that different mechanisms may operate for presentation of high and low affinity peptides by TAP-competent cells. High affinity peptides can apparently compete with peptides in preloaded MHC class I molecules at the cell surface, whereas low affinity peptides require empty MHC molecules within cells. Accordingly, very high concentrations of exogenous low affinity peptides in conjunction with active MHC class I metabolism were required to allow successful presentation against a background of competing intracellular high affinity peptides in TAP-competent cells. These findings have implications for the design of peptide and protein-based vaccines.
authors.affiliation: Melbourne Tumor Biology Branch, Ludwig Institute for Cancer Research, Austin and Repatriation Medical Centre, Heidelberg, Victoria, Australia. Thomas_Luft@med.uni-heidelberg.de
authors.forename: T
authors.initials: T
authors.lastname: Luft
authors.forename: M
authors.initials: M
authors.lastname: Rizkalla
authors.forename: T Y
authors.initials: TY
authors.lastname: Tai
authors.forename: Q
authors.initials: Q
authors.lastname: Chen
authors.forename: R I
authors.initials: RI
authors.lastname: MacFarlan
authors.forename: I D
authors.initials: ID
authors.lastname: Davis
authors.forename: E
authors.initials: E
authors.lastname: Maraskovsky
authors.forename: J
authors.initials: J
authors.lastname: Cebon
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000276:immunology* / Q000378:metabolism*; D000595:Amino Acid Sequence; D017951:Antigen Presentation / Q000502:physiology*; D000951:Antigens, Neoplasm; D001667:Binding, Competitive; D002454:Cell Differentiation; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D015789:HLA-A2 Antigen / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D007700:Kinetics; D058965:MART-1 Antigen; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010455:Peptides / Q000276:immunology* / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D000951:Antigens, Neoplasm; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D058965:MART-1 Antigen; C548667:MLANA protein, human; D009363:Neoplasm Proteins; D010455:Peptides; C073119:TAP1 protein, human; D007371:Interferon-gamma