title: Localization of peptide/MHC class II complexes in macrophages following antigen processing of viable Streptococcus pyogenes.
abstract: The subcellular localization of peptide/MHC complexes was investigated during processing of the surface M5 protein from Streptococcus pyogenes. Bone marrow-derived macrophages were pulsed with viable S. pyogenes for 20 min followed by various periods of chase. T hybridoma cells detected complexes of one epitope, M5(17-31) with E(d) on the surface of macrophages within 30 min of chase. In contrast, complexes with another epitope, M5(308-319) with A(d) peaked later. Intracellular localization of peptide/MHC-II complexes was studied by subcellular fractionation and detection of complexes in fractions by T hybridoma cells. M5(17-31)/E(d) complexes were detected in light membrane fractions containing plasma membrane and early endosomes by 10-30 min. M5(308-319)/A(d) complexes were detected in these light membranes after 3 h of chase. Thus, the time course of M5(308-319)/A(d) presentation was delayed relative to M5(17-31)/E(d). However, neither type of complex was detected at any time in fractions containing phagosomes. Both species of peptide/MHC complexes localized to endocytic compartments, indicating a role for endosomes in presentation of antigens from phagocytosed bacteria.
authors.affiliation: School of Clinical Medical Sciences (Rheumatology), University of Newcastle upon Tyne, Newcastle upon Tyne, GB.
authors.forename: Alexei
authors.initials: A
authors.lastname: von Delwig
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Ramachandra
authors.forename: Clifford V
authors.initials: CV
authors.lastname: Harding
authors.forename: John H
authors.initials: JH
authors.lastname: Robinson
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology / Q000502:physiology; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D011992:Endosomes / Q000276:immunology / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides / Q000378:metabolism*; D010588:Phagosomes / Q000276:immunology / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D000949:Histocompatibility Antigens Class II; D010455:Peptides; C014689:streptococcal M protein