title: Antigen stored in dendritic cells after macropinocytosis is released unprocessed from late endosomes to target B cells.
abstract: B lymphocytes can be triggered in lymph nodes by nonopsonized antigens (Ag), potentially in their native form. However, the mechanisms that promote encounter of B lymphocytes with unprocessed antigens in lymph nodes are still elusive. We show here that antigens are detected in B cells in the draining lymph nodes of mice injected with live, but not fixed, dendritic cells (DCs) loaded with antigens. This highlights active processes in DCs to promote Ag transfer to B lymphocytes. In addition, antigen-loaded DCs found in the draining lymph node were CD103+. Using 3 different model Ag, we then show that immature DCs efficiently take up Ag by macropinocytosis and store the internalized material in late endocytic compartments. We find that DCs have a unique ability to release antigens from these compartments in the extracellular medium, which is controlled by Rab27. B cells take up the regurgitated Ag and the chemokine CXCL13, essential to attract B cells in lymph nodes, enhances this transfer. Our results reveal a unique property of DCs to regurgitate unprocessed Ag that could play an important role in B-cell activation.
authors: Inserm U1016, Institut Cochin, Paris, France.
authors: Delphine
authors: D
authors: Le Roux
authors: Agnès
authors: A
authors: Le Bon
authors: Audrey
authors: A
authors: Dumas
authors: Kahina
authors: K
authors: Taleb
authors: Martin
authors: M
authors: Sachse
authors: Romain
authors: R
authors: Sikora
authors: Marion
authors: M
authors: Julithe
authors: Alexandre
authors: A
authors: Benmerah
authors: Georges
authors: G
authors: Bismuth
authors: Florence
authors: F
authors: Niedergang
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000941:Antigens / Q000276:immunology*; D015703:Antigens, CD / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D054382:Chemokine CXCL13 / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D039001:Integrin alpha Chains / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D008198:Lymph Nodes / Q000276:immunology*; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D010873:Pinocytosis / Q000276:immunology*
chemical_list: D000941:Antigens; D015703:Antigens, CD; D054382:Chemokine CXCL13; D039001:Integrin alpha Chains; C091367:alpha E integrins