title: Transport and intracellular distribution of MHC class II molecules and associated invariant chain in normal and antigen-processing mutant cell lines.
abstract: We have compared the intracellular transport and subcellular distribution of MHC class II-invariant chain complexes in a wild-type HLA-DR3 homozygous cell line and a mutant cell line, T2.DR3. The latter has a defect in antigen processing and accumulates HLA-DR3 molecules associated with an invariant chain-derived peptide (CLIP) rather than the normal complement of peptides derived from endocytosed proteins. We find that in the wild-type cells, CLIP is transiently associated with HLA-DR3 molecules, suggesting that the peptide is a normal class II-associated intermediate generated during proteolysis of the invariant chain. In the mutant cell line proteolysis of the invariant chain is less efficient, and HLA-DR3/CLIP complexes are generated much more slowly. Examination of the mutant cell line by immunoelectronmicroscopy shows that class II-invariant chain complexes accumulate intracellularly in large acidic vesicles which contain lysosomal markers, including beta-hexosaminidase, cathepsin D, and the lysosomal membrane protein CD63. The markers in these vesicles are identical to those seen in the class II-containing vesicles (MIICs) seen in the wild-type cells but the morphology is drastically different. The vesicles in the mutant cells are endocytic, as measured by the internalization of BSA-gold conjugates. The implication of these findings for antigen processing in general and the nature of the mutation in particular are discussed.
authors.affiliation: Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: J M
authors.initials: JM
authors.lastname: Riberdy
authors.forename: R R
authors.initials: RR
authors.lastname: Avva
authors.forename: H J
authors.initials: HJ
authors.lastname: Geuze
authors.forename: P
authors.initials: P
authors.lastname: Cresswell
mesh_terms: D017951:Antigen Presentation / Q000235:genetics*; D000944:Antigens, Differentiation, B-Lymphocyte; D001402:B-Lymphocytes / Q000276:immunology* / Q000648:ultrastructure; D001692:Biological Transport; D015415:Biomarkers; D002460:Cell Line; D004705:Endocytosis; D005629:Frozen Sections; D015803:HLA-DR3 Antigen / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009154:Mutation; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D015415:Biomarkers; D015803:HLA-DR3 Antigen; D000949:Histocompatibility Antigens Class II; D010446:Peptide Fragments; C045084:invariant chain