title: CD11c+ antigen presenting cells from the alveolar space, lung parenchyma and spleen differ in their phenotype and capabilities to activate naïve and antigen-primed T cells.
abstract: BACKGROUND
  The lung is divided into two major compartments: the alveolar space and the parenchyma. The alveolar macrophages are the first line of leukocytes in the lung taking up incoming microbes or microbial antigens whereas the parenchymal dendritic cells (DCs) are believed to be the sole potent antigen presenting cells (APCs) in the lung. Both resting alveolar macrophages and parenchymal DCs express CD11c. Several important questions remain to be elucidated: 1] to which extent the alveolar space and lung parenchymal CD11c+ APCs differ in their phenotype and ability to activate naïve T cells; 2] whether they differ in their ability to activate antigen-experienced or -primed T cells; and 3] whether these lung CD11c+ APC populations differ from the splenic CD11c+ APCs which have been commonly used for understanding APC biology.
  
  
  RESULTS
  CD11c+ APCs from the alveolar space, lung parenchyma, and the spleen display differential co-stimulatory molecule expression and cytokine responsiveness upon stimulation. Alveolar space APCs are weak activators of naïve T cells compared to lung parenchymal and splenic CD11c+ APC populations. However, alveolar space APCs are able to potently activate the in vivo microbial antigen-primed T cells to a similar extent as lung parenchymal and splenic APCs.
  
  
  CONCLUSIONS
  Together our findings indicate that alveolar CD11c+ APCs have a specialized T cell-activating function, capable of activating antigen-primed, but not naïve, T cells whereas lung CD11c+ APCs are capable of activating both the naïve and antigen-primed T cell populations.
authors.affiliation: Department of Pathology and Molecular Medicine, Centre for Gene Therapeutics, McMaster University, Hamilton, Ontario, Canada. kugatk@mcmaster.ca
authors.forename: Kapilan
authors.initials: K
authors.lastname: Kugathasan
authors.forename: Elizabeth K
authors.initials: EK
authors.lastname: Roediger
authors.forename: Cherrie-Lee
authors.initials: CL
authors.lastname: Small
authors.forename: Sarah
authors.initials: S
authors.lastname: McCormick
authors.forename: Pingchang
authors.initials: P
authors.lastname: Yang
authors.forename: Zhou
authors.initials: Z
authors.lastname: Xing
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism*; D018845:CD11 Antigens / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism*; D005260:Female; D007156:Immunologic Memory; D008070:Lipopolysaccharides / Q000378:metabolism; D008168:Lung / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009928:Organ Specificity; D010047:Ovalbumin; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D037182:T-Cell Antigen Receptor Specificity / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism
chemical_list: D018845:CD11 Antigens; D008070:Lipopolysaccharides; D010047:Ovalbumin