title: Rapid downregulation of antigen processing enzymes in ex vivo generated human monocyte derived dendritic cells occur endogenously in extended cultures.
abstract: Dendritic cells, the most potent antigen presenting cells, have been shown in murine models to induce immune responses against many antigens. Their role in the initiation of antitumour immunity has received enormous attention. Their ability to process and present antigen is dependent on their state of maturation. This study examines the activity of human monocyte-derived dendritic cells at two different time points and the corresponding changes in the proteolytic enzyme activity. Dendritic cells were produced from peripheral blood mononuclear cells of normal volunteers. Plastic adherent cells were cultured for 5 or 7 days with recombinant human (rh)GM-CSF and rhIL-4. Flow cytometry showed that day 5 dendritic cells (DC) were less mature than day 7 DC as indicated by the expression of CD1a, CD11c, CD14, CD80, CD83, CD86 and MHC-II. Proteolytic activity of the enzymes cathepsin C and cathepsin G and phagocytosis of particulate antigens also showed significant differences between d5 dendritic cells and d7 dendritic cells. Allogeneic costimulatory activity of d7 dendritic cells was also significantly increased. Induction of immunity requires active presentation of antigens by antigen processing cells on their MHC-I and/or MHC-II molecules. Study of peptide carriers and peptide precursor molecules showed a significant decrease in CLIP levels in the day 7 DC, suggesting their decreased ability to process antigens but no difference in their ability to load MHC-II molecules. These findings indicate that the length of time in culture, in the absence of exogenous maturation - inducing stimuli affects dendritic cell maturation. Intracellular enzymatic activities of dendritic cells also changed rapidly with small changes in phenotype.
authors.affiliation: Dermatology Laboratories, Melanoma and Skin Cancer Research Institute, Royal Prince Alfred Hospital, University of Sydney, NSW, Australia.
authors.forename: R K
authors.initials: RK
authors.lastname: Ishri
authors.forename: Scott
authors.initials: S
authors.lastname: Menzies
authors.forename: Peter
authors.initials: P
authors.lastname: Hersey
authors.forename: Gary M
authors.initials: GM
authors.lastname: Halliday
mesh_terms: D017951:Antigen Presentation / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D015536:Down-Regulation / Q000276:immunology; D004798:Enzymes / Q000276:immunology* / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D009000:Monocytes / Q000166:cytology; D009369:Neoplasms / Q000276:immunology; D010455:Peptides / Q000276:immunology
chemical_list: D015703:Antigens, CD; D004798:Enzymes; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; D010455:Peptides