title: Rab17 mediates differential antigen sorting following efferocytosis and phagocytosis.
abstract: Macrophages engulf and destroy pathogens (phagocytosis) and apoptotic cells (efferocytosis), and can subsequently initiate adaptive immune responses by presenting antigens derived from engulfed materials. Both phagocytosis and efferocytosis share a common degradative pathway in which the target is engulfed into a membrane-bound vesicle, respectively, termed the phagosome and efferosome, where they are degraded by sequential fusion with endosomes and lysosomes. Despite this shared maturation pathway, macrophages are immunogenic following phagocytosis but not efferocytosis, indicating that differential processing or trafficking of antigens must occur. Mass spectrometry and immunofluorescence microscopy of efferosomes and phagosomes in macrophages demonstrated that efferosomes lacked the proteins required for antigen presentation and instead recruited the recycling regulator Rab17. As a result, degraded materials from efferosomes bypassed the MHC class II loading compartment via the recycling endosome - a process not observed in phagosomes. Combined, these results indicate that macrophages prevent presentation of apoptotic cell-derived antigens by preferentially trafficking efferocytosed, but not phagocytosed, materials away from the MHC class II loading compartment via the recycling endosome pathway.
authors.affiliation: Department of Microbiology and Immunology and The Centre for Human Immunology, The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada N6A 5C1.
authors.forename: Charles
authors.initials: C
authors.lastname: Yin
authors.affiliation: Department of Microbiology and Immunology and The Centre for Human Immunology, The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada N6A 5C1.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology and The Centre for Human Immunology, The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada N6A 5C1.
authors.forename: Dean
authors.initials: D
authors.lastname: Argintaru
authors.affiliation: Department of Microbiology and Immunology and The Centre for Human Immunology, The University of Western Ontario, Schulich School of Medicine and Dentistry, London, ON, Canada N6A 5C1.
authors.forename: Bryan
authors.initials: B
authors.lastname: Heit
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D000941:Antigens / Q000378:metabolism*; D017209:Apoptosis; D002460:Cell Line; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D010587:Phagocytosis; D010588:Phagosomes / Q000378:metabolism; D021381:Protein Transport; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000941:Antigens; D020691:rab GTP-Binding Proteins