title: Class I HLA folding and antigen presentation in beta 2-microglobulin-defective Daudi cells.
abstract: To present virus and tumor Ags, HLA class I molecules undergo a complex multistep assembly involving discrete but transient folding intermediates. The most extensive folding abnormalities occur in cells lacking the class I L chain subunit, called beta(2)-microglobulin (beta(2)m). Herein, this issue was investigated taking advantage of eight conformational murine mAbs (including the prototypic W6/32 mAb) to mapped H chain epitopes of class I molecules, four human mAbs to class I alloantigens, as well as radioimmunoprecipitation, in vitro assembly, pulse-chase, flow cytometry, and peptide-pulse/ELISPOT experiments. We show that endogenous (HLA-A1, -A66, and -B58) as well as transfected (HLA-A2) heavy chains in beta(2)m-defective Burkitt lymphoma Daudi cells are capable of being expressed on the cell surface, although at low levels, and exclusively as immature glycoforms. In addition, HLA-A2 is: 1) partially folded at crucial interfaces with beta(2)m, peptide Ag, and CD8; 2) receptive to exogenous peptide; and 3) capable of presenting exogenous peptide epitopes (from virus and tumor Ags) to cytotoxic T lymphocytes (bulk populations as well as clones) educated in a beta(2)m-positive environment. These experiments demonstrate a precursor-product relationship between novel HLA class I folding intermediates, and define a stepwise mechanism whereby distinct interfaces of the class I H chain undergo successive, ligand-induced folding adjustments in vitro as well as in vivo. Due to this unprecedented class I plasticity, Daudi is the first human cell line in which folding and function of class I HLA molecules are observed in the absence of beta(2)m. These findings bear potential implications for tumor immunotherapy.
authors.affiliation: Laboratory of Immunology, Regina Elena Cancer Institute Centro della Ricerca Sperimentale, Rome, Italy.
authors.forename: Aline
authors.initials: A
authors.lastname: Martayan
authors.forename: Leonardo
authors.initials: L
authors.lastname: Sibilio
authors.forename: Elisa
authors.initials: E
authors.lastname: Tremante
authors.forename: Elisa
authors.initials: E
authors.lastname: Lo Monaco
authors.forename: Arend
authors.initials: A
authors.lastname: Mulder
authors.forename: Doriana
authors.initials: D
authors.lastname: Fruci
authors.forename: Agata
authors.initials: A
authors.lastname: Cova
authors.forename: Licia
authors.initials: L
authors.lastname: Rivoltini
authors.forename: Patrizio
authors.initials: P
authors.lastname: Giacomini
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D017951:Antigen Presentation / Q000235:genetics* / Q000276:immunology; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000276:immunology; D006680:HLA Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015788:HLA-A1 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D015789:HLA-A2 Antigen / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D015235:HLA-B Antigens / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D017510:Protein Folding; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D001613:beta 2-Microglobulin / Q000172:deficiency* / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D015788:HLA-A1 Antigen; D015789:HLA-A2 Antigen; D015235:HLA-B Antigens; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D011498:Protein Precursors; D001613:beta 2-Microglobulin