title: Quantum dots for tracking dendritic cells and priming an immune response in vitro and in vivo.
abstract: Dendritic cells (DCs) play a key role in initiating adaptive immune response by presenting antigen to T cells in lymphoid organs. Here, we investigate the potential of quantum dots (QDs) as fluorescent nanoparticles for in vitro and in vivo imaging of DCs, and as a particle-based antigen-delivery system to enhance DC-mediated immune responses. We used confocal, two-photon, and electron microscopies to visualize QD uptake into DCs and compared CD69 expression, T cell proliferation, and IFN-gamma production by DO11.10 and OT-II T cells in vivo in response to free antigen or antigen-conjugated to QDs. CD11c(+) DCs avidly and preferentially endocytosed QDs, initially into small vesicles near the plasma membrane by an actin-dependent mechanism. Within 10 min DCs contained vesicles of varying size, motion, and brightness distributed throughout the cytoplasm. At later times, endocytosed QDs were compartmentalized inside lysosomes. LPS-induced maturation of DCs reduced the rate of endocytosis and the proportion of cells taking up QDs. Following subcutaneous injection of QDs in an adjuvant depot, DCs that had endocytosed QDs were visualized up to 400 microm deep within draining lymph nodes. When antigen-conjugated QDs were used, T cells formed stable clusters in contact with DCs. Antigen-conjugated QDs induced CD69 expression, T cell proliferation, and IFN-gamma production in vivo with greater efficiency than equivalent amounts of free antigen. These results establish QDs as a versatile platform for immunoimaging of dendritic cells and as an efficient nanoparticle-based antigen delivery system for priming an immune response.
authors.affiliation: Department of Physiology and Biophysics, University of California Irvine, Irvine, California, United States of America.
authors.forename: Debasish
authors.initials: D
authors.lastname: Sen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Deerinck
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ellisman
authors.forename: Ian
authors.initials: I
authors.lastname: Parker
authors.forename: Michael D
authors.initials: MD
authors.lastname: Cahalan
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D003713:Dendritic Cells / Q000166:cytology / Q000502:physiology*; D004705:Endocytosis; D007107:Immune System / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008954:Models, Biological; D045663:Quantum Dots; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D007371:Interferon-gamma