title: Characterization of fibroblasts with a unique defect in processing antigens with disulfide bonds.
abstract: A chinese hamster ovary (CHO) fibroblast, transfected with murine MHC class II genes, inefficiently stimulated CD4+ Th cells specific for OVA, hen egg lysozyme (HEL), and pork insulin which contain disulfide bonds. However, the fibroblasts elicited a T cell response to lambda repressor, which lacks disulfide bonds, and efficiently presented synthetic peptides. A somatic cell hybrid WALC, generated by fusing the hamster fibroblast with a murine L cell fibroblast, very efficiently processed OVA and HEL, suggesting that impaired processing was genetically complemented and was a recessive trait. The hamster fibroblasts were capable of processing two distinct denatured forms of OVA and carboxymethylated HEL, either as effectively or more efficiently than the B lymphoma cell. The CHO cells also displayed diminished disulfide reduction of an endocytosed [125I]tyramine linked to poly-(D-lysine) through a disulfide spacer compared with that of the cell hybrid, providing direct evidence for defective reductive cleavage by the CHO cells. Diminished aspartic acid-mediated proteolysis of Ag could not account for the phenotype, because cell lysates and separated organelles from the fibroblast possessed higher acidic aspartyl proteolytic activity than lysates and organelles from a B lymphoma cell. Thus, CHO cells exhibit a defect in processing Ag with disulfide bonds which is consistent with the impaired intracellular reduction of the disulfide bonds in endocytosed macromolecules.
authors.affiliation: Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond 23298.
authors.forename: B J
authors.initials: BJ
authors.lastname: Merkel
authors.forename: R
authors.initials: R
authors.lastname: Mandel
authors.forename: H J
authors.initials: HJ
authors.lastname: Ryser
authors.forename: K L
authors.initials: KL
authors.lastname: McCoy
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D000941:Antigens / Q000737:chemistry / Q000276:immunology*; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D016466:CHO Cells / Q000276:immunology* / Q000378:metabolism; D002645:Chickens; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics; D003553:Cystine / Q000737:chemistry*; D004268:DNA-Binding Proteins; D004220:Disulfides; D004705:Endocytosis; D005808:Genes, Recessive; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D006822:Hybrid Cells / Q000276:immunology; D006825:Hybridomas; D007328:Insulin / Q000737:chemistry / Q000276:immunology; D007739:L Cells; D051379:Mice; D009113:Muramidase / Q000737:chemistry / Q000276:immunology; D010047:Ovalbumin / Q000737:chemistry / Q000276:immunology; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000276:immunology; D012097:Repressor Proteins / Q000276:immunology; D013552:Swine; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D000941:Antigens; D004268:DNA-Binding Proteins; D004220:Disulfides; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D007328:Insulin; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D003553:Cystine; D010047:Ovalbumin; D009113:Muramidase; D016282:Aspartic Acid Endopeptidases