title: Distribution of productive antigen-processing activity for MHC class II presentation in macrophages.
abstract: We demonstrated that an epitope from the recombinant protective antigen (rPA) of Bacillus anthracis was presented by mature major histocompatibility complex class II (MHC-II) molecules, whereas an epitope from the recombinant virulent (rV) antigen of Yersinia pestis was presented by newly synthesized MHC-II. We addressed which endosomal compartments were involved in the antigen processing of each epitope. Bone-marrow-derived macrophages were subjected to subcellular fractionation; fractions were analysed for the expression of endosomal markers and used as a source of enzyme activity for the processing of rPA and rV antigens. The rPA epitope was productively processed by dense lysosomal fractions and light membrane fractions expressing early endosomal markers Rab5 and early endosomal antigen-1 as well as markers of antigen-presenting compartments (MHC-II, DM, DO and Ii chain). In contrast, the rV epitope was productively processed only by dense fractions with lysosomal activity. No productive antigen-processing activity was associated with fractions of intermediate density expressing Rab7 and Rab9, characteristic of late endosomes. The data suggest that endosomal compartments expressing Rab5 guanosine triphosphatase can productively process protein antigens for presentation by mature MHC class II molecules.
authors.affiliation: Musculoskeletal Research Group, Clinical Medical Sciences, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne, UK. alexei.delwig@ncl.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: von Delwig
authors.forename: J A
authors.initials: JA
authors.lastname: Musson
authors.forename: H-K
authors.initials: HK
authors.lastname: Shim
authors.forename: J J
authors.initials: JJ
authors.lastname: Lee
authors.forename: N
authors.initials: N
authors.lastname: Walker
authors.forename: C V
authors.initials: CV
authors.lastname: Harding
authors.forename: E D
authors.initials: ED
authors.lastname: Williamson
authors.forename: J H
authors.initials: JH
authors.lastname: Robinson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D000942:Antigens, Bacterial / Q000032:analysis / Q000276:immunology*; D001408:Bacillus anthracis / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D011992:Endosomes / Q000276:immunology; D018984:Epitopes, T-Lymphocyte / Q000032:analysis; D000949:Histocompatibility Antigens Class II / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000032:analysis / Q000378:metabolism; D015010:Yersinia pestis / Q000276:immunology*; D020691:rab GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D018984:Epitopes, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; D011994:Recombinant Proteins; D020691:rab GTP-Binding Proteins