title: Size-dependent accumulation of particles in lysosomes modulates dendritic cell function through impaired antigen degradation.
abstract: BACKGROUND
  Nanosized particles may enable therapeutic modulation of immune responses by targeting dendritic cell (DC) networks in accessible organs such as the lung. To date, however, the effects of nanoparticles on DC function and downstream immune responses remain poorly understood.
  
  
  METHODS
  Bone marrow-derived DCs (BMDCs) were exposed in vitro to 20 or 1,000 nm polystyrene (PS) particles. Particle uptake kinetics, cell surface marker expression, soluble protein antigen uptake and degradation, as well as in vitro CD4(+) T-cell proliferation and cytokine production were analyzed by flow cytometry. In addition, co-localization of particles within the lysosomal compartment, lysosomal permeability, and endoplasmic reticulum stress were analyzed.
  
  
  RESULTS
  The frequency of PS particle-positive CD11c(+)/CD11b(+) BMDCs reached an early plateau after 20 minutes and was significantly higher for 20 nm than for 1,000 nm PS particles at all time-points analyzed. PS particles did not alter cell viability or modify expression of the surface markers CD11b, CD11c, MHC class II, CD40, and CD86. Although particle exposure did not modulate antigen uptake, 20 nm PS particles decreased the capacity of BMDCs to degrade soluble antigen, without affecting their ability to induce antigen-specific CD4(+) T-cell proliferation. Co-localization studies between PS particles and lysosomes using laser scanning confocal microscopy detected a significantly higher frequency of co-localized 20 nm particles as compared with their 1,000 nm counterparts. Neither size of PS particle caused lysosomal leakage, expression of endoplasmic reticulum stress gene markers, or changes in cytokines profiles.
  
  
  CONCLUSIONS
  These data indicate that although supposedly inert PS nanoparticles did not induce DC activation or alteration in CD4(+) T-cell stimulating capacity, 20 nm (but not 1,000 nm) PS particles may reduce antigen degradation through interference in the lysosomal compartment. These findings emphasize the importance of performing in-depth analysis of DC function when developing novel approaches for immune modulation with nanoparticles.
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland ; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
authors.forename: Emilie
authors.initials: E
authors.lastname: Seydoux
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland ; Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Rothen-Rutishauser
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland.
authors.forename: Izabela M
authors.initials: IM
authors.lastname: Nita
authors.affiliation: Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland.
authors.forename: Sandor
authors.initials: S
authors.lastname: Balog
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland.
authors.forename: Amiq
authors.initials: A
authors.lastname: Gazdhar
authors.affiliation: School of Veterinary and Life Sciences, Molecular and Biomedical Sciences, Murdoch University, Perth, WA, Australia ; Telethon Kids Institute, Perth, WA, Australia.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Stumbles
authors.affiliation: Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland ; Department of Chemistry, University of Fribourg, Fribourg, Switzerland.
authors.forename: Alke
authors.initials: A
authors.lastname: Petri-Fink
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland.
authors.forename: Fabian
authors.initials: F
authors.lastname: Blank
authors.affiliation: Department of Respiratory Medicine, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: von Garnier
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects*; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D053758:Nanoparticles / Q000737:chemistry* / Q000633:toxicity; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D011137:Polystyrenes
keywords: CD4+ T-cells; immune modulation; mouse dendritic cells; nanoparticles; polystyrene particles