title: Two preferentially expressed proteins protect vascular endothelial cells from an attack by peptide-specific CTL.
abstract: Vascular endothelial cells (EC) are an exposed tissue with intimate contact with circulating Ag-specific CTL. Experimental in vitro and clinical data suggested that endothelial cells present a different repertoire of MHC class I-restricted peptides compared with syngeneic leukocytes or epithelial cells. This endothelial-specific peptide repertoire might protect EC from CTL-mediated cell death. The HLA-A*02-restricted peptide profile of human EC and syngeneic B lymphoblastoid cells was biochemically analyzed and compared. For EC selective peptides, source protein expression, peptide binding affinity, and peptide-HLA-A*02 turnover were measured. The significance of abundant peptide presentation for target cell recognition by immunodominant CTL was tested by small interfering RNA treatment of EC to knock down the source proteins. High amounts of two peptides, PTRF(56-64) and CD59(106-114), were consistently detected in EC. This predominance of two endothelial peptides was explained by cell type-specific source protein expression that compensated for poor HLA-A*02 binding affinity and short half-live of peptide/HLA-A*02 complexes. Knocking down the source proteins containing the abundant endothelial peptide motifs led to a nearly 100-fold increase of surface expression of SMCY(311-319), an immunodominant minor histocompatibility Ag, as detected by cytotoxicity assays using SMCY(311-319)-specific CTL. We conclude that EC express and present preferentially two distinct HLA-A*02-restricted peptides at extraordinary high levels. These abundant self-peptides may protect EC from CTL-mediated lysis by competing for HLA-A*02 binding sites with immunodominant scarcely expressed antigenic peptides.
authors.affiliation: Department of Biomedicine, University of Basel, CH-4031 Basel, Switzerland.
authors.forename: Daniela S
authors.initials: DS
authors.lastname: Thommen
authors.forename: Heiko
authors.initials: H
authors.lastname: Schuster
authors.forename: Mario
authors.initials: M
authors.lastname: Keller
authors.forename: Sarika
authors.initials: S
authors.lastname: Kapoor
authors.forename: Andreas O
authors.initials: AO
authors.lastname: Weinzierl
authors.forename: Cuddapah S
authors.initials: CS
authors.lastname: Chennakesava
authors.forename: Xueya
authors.initials: X
authors.lastname: Wang
authors.forename: Lucia
authors.initials: L
authors.lastname: Rohrer
authors.forename: Arnold
authors.initials: A
authors.lastname: von Eckardstein
authors.forename: Stefan
authors.initials: S
authors.lastname: Stevanovic
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Biedermann
mesh_terms: D001667:Binding, Competitive / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D004730:Endothelium, Vascular / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D015789:HLA-A2 Antigen / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D016056:Immunodominant Epitopes / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D010446:Peptide Fragments / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding / Q000276:immunology; D021241:Spectrometry, Mass, Electrospray Ionization; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism / Q000473:pathology
chemical_list: D015789:HLA-A2 Antigen; D016056:Immunodominant Epitopes; D010446:Peptide Fragments