title: Optimizing the exogenous antigen loading of monocyte-derived dendritic cells.
abstract: Dendritic cell (DC) vaccination, i.e. the adoptive transfer of antigen-loaded DC, is still at an early stage and requires standardization. In this study, we investigated the exogenous loading of monocyte-derived DCs with HLA class I- and II-restricted peptides, as despite widespread use, little effort has been put into its pre-clinical validation. We found that only mature DCs (m-DC) but not immature DCs (im-DC) could be sufficiently loaded with exogenous class I-restricted peptides and were by far superior in expanding CD8(+) primary (Melan-A.A2 peptide-specific) and recall [Influenza matrix peptide (IMP) A2-specific] T cell responses. Primary stimulation with peptide-loaded im-DCs even down-regulated antigen-specific T cell responses. Our results indicate that stimulation with m-DCs is superior in terms of quantity and quality compared with im-DCs, supporting their preferred use in clinical DC trials. Loading of m-DCs with high (10 microM) concentrations generated clearly more Melan-A effectors than loading with 1 or 0.1 microM without any negative effect on the quality (affinity) of the resulting T cells. In contrast to the findings with the Melan-A peptide loading with 10 microM IMP was counter-productive, induced apoptosis and yielded fewer specific T cells of inferior affinity as compared with loading with 1 or 0.1 microM. In sharp contrast to the situation for HLA class I, much higher levels and longer half-lives of peptide-HLA class II complexes were obtainable upon loading of im-DCs with exogenous peptide, but m-DCs were functionally preferable to induce T(h)1 responses in vitro. Another surprising finding was that, while presentation to T cells upon simultaneous loading of several peptides with highly varying affinities and competing for the same class I or II molecule was possible, in priming experiments peptide competition clearly inhibited T cell induction. Although peptides will obviously vary in their individual properties, our study clearly points to some important principles that should be taken into account.
authors.affiliation: Department of Dermatology, University Hospital Erlangen, Erlangen, Germany. detlef.dieckmann@derma.imed.uni-erlangen.de
authors.forename: Detlef
authors.initials: D
authors.lastname: Dieckmann
authors.forename: Erwin S
authors.initials: ES
authors.lastname: Schultz
authors.forename: Bernhard
authors.initials: B
authors.lastname: Ring
authors.forename: Patrick
authors.initials: P
authors.lastname: Chames
authors.forename: Gerhard
authors.initials: G
authors.lastname: Held
authors.forename: Hennie R
authors.initials: HR
authors.lastname: Hoogenboom
authors.forename: Gerold
authors.initials: G
authors.lastname: Schuler
mesh_terms: D000906:Antibodies / Q000276:immunology; D017951:Antigen Presentation; D000941:Antigens / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology*; D006649:Histocompatibility Antigens / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D058965:MART-1 Antigen; D058950:Melanoma-Specific Antigens; D009000:Monocytes / Q000276:immunology*; D009363:Neoplasm Proteins / Q000276:immunology; D010455:Peptides / Q000276:immunology; D013745:Tetanus Toxoid / Q000276:immunology; D014763:Viral Matrix Proteins / Q000276:immunology
chemical_list: D000906:Antibodies; D000941:Antigens; D000951:Antigens, Neoplasm; D006649:Histocompatibility Antigens; C072011:MAGEA1 protein, human; C072013:MAGEA3 protein, human; D058965:MART-1 Antigen; C548667:MLANA protein, human; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D010455:Peptides; D013745:Tetanus Toxoid; D014763:Viral Matrix Proteins; D007371:Interferon-gamma