title: Peptide loading onto recycling HLA-DR molecules occurs in early endosomes.
abstract: Presentation of exogenous antigens to MHC class II-restricted T cells can follow two different processing pathways. The classical pathway requires newly synthesized MHC class II molecules, invariant chain and HLA-DM expression, whereas the alternative pathway is independent of protein synthesis, invariant chain and HLA-DM. In both cases, MHC class II molecules associate with peptides derived from exogenous antigens that have been processed in endocytic compartments. Different endosomal/prelysosomal compartments where peptide/MHC class II complexes and HLA-DM molecules accumulate have been described. We show here that the alternative pathway uses an earlier compartment than the classical pathway. Experiments with chemically cross-linked antigen suggest that recycling MHC class II molecules present rapidly degraded antigens, leading to a rapid immune response to exogenously added influenza virus proteins.
authors.affiliation: Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, USA. pinet@montp.inserm.fr
authors.forename: V M
authors.initials: VM
authors.lastname: Pinet
authors.forename: E O
authors.initials: EO
authors.lastname: Long
mesh_terms: D000956:Antigens, Viral / Q000378:metabolism; D002451:Cell Compartmentation; D002460:Cell Line; D003432:Cross-Linking Reagents; D011992:Endosomes / Q000378:metabolism*; D018604:Epitope Mapping; D006684:HLA-DR Antigens / Q000378:metabolism*; D006389:Hemagglutinins, Viral / Q000276:immunology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010455:Peptides / Q000276:immunology; D014763:Viral Matrix Proteins / Q000276:immunology
chemical_list: D000956:Antigens, Viral; D003432:Cross-Linking Reagents; D006684:HLA-DR Antigens; D006389:Hemagglutinins, Viral; D008565:Membrane Proteins; D010455:Peptides; D014763:Viral Matrix Proteins