title: Different endocytic compartments are involved in the tight association of class II molecules with processed hen egg lysozyme and ribonuclease A in B cells.
abstract: The processing of exogenous antigens and the association of peptides with class II molecules both occur within the endocytic pathway. 2A4 B lymphoma cells of the H-2k haplotype were grown in the presence or the absence of two different exogenous antigens (hen egg lysozyme and ribonuclease A) internalized by fluid-phase endocytosis. Using subcellular fractionation techniques, we demonstrate that, in the presence of hen egg lysozyme, newly synthesized SDS-stable class II molecules are detected in a dense endocytic compartment which does not have the characteristics of neither early and late endosomes nor lysosomes. In contrast, no SDS-stable class II molecules are observed between ribonuclease A and newly synthesized class II molecules. Interestingly, when class II molecules are analyzed at steady state, SDS-stable class II molecules induced by ribonuclease A are found in a compartment cosedimenting with late endosomes. These results suggest that the tight associations between ribonuclease A or hen egg lysozyme with class II molecules occur in distinct endocytic compartments and that these associations may depend on the sensitivity of antigens to proteolysis.
authors.affiliation: Centre d'Immunologie INSERM-CNRS de Marseille Luminy, France.
authors.forename: J M
authors.initials: JM
authors.lastname: Escola
authors.forename: J C
authors.initials: JC
authors.lastname: Grivel
authors.forename: P
authors.initials: P
authors.lastname: Chavrier
authors.forename: J P
authors.initials: JP
authors.lastname: Gorvel
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D001402:B-Lymphocytes / Q000502:physiology* / Q000648:ultrastructure; D001692:Biological Transport; D002451:Cell Compartmentation; D002645:Chickens; D004705:Endocytosis; D000949:Histocompatibility Antigens Class II / Q000502:physiology*; D016393:Lymphoma, B-Cell; D051379:Mice; D009113:Muramidase / Q000276:immunology*; D012259:Ribonuclease, Pancreatic / Q000276:immunology*; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured
chemical_list: D000949:Histocompatibility Antigens Class II; D012259:Ribonuclease, Pancreatic; D009113:Muramidase