title: Conformation of human leucocyte antigen-C molecules at the surface of human trophoblast cells.
abstract: Human leucocyte antigen (HLA)-C is expressed at lower levels than other classical HLA-I molecules on somatic cells. Surface HLA-C proteins can occur as conventionally beta(2)-microglobulin (beta2m)-associated complexes or as open conformers dissociated from peptide and/or beta(2)m. We investigated the conformation of HLA-C molecules on normal human trophoblast cells, which invade the maternal decidua during placentation. A panel of monoclonal antibodies to different conformations of HLA-I molecules was used in flow cytometry and surface immunoprecipitation experiments. On the surface of trophoblast cells only beta(2)m-associated complexes of HLA-C molecules were detected. In contrast, both open conformers and beta(2)m-associated HLA-C could be detected on other cells from the decidua, HLA-C-transfectants and cell lines. The levels of HLA-C expressed on primary trophoblast cells could be detected by antibodies specific to non-beta(2)m-associated conformations because binding was seen after acid-induced denaturation of surface proteins. In contrast to HLA-G molecules on trophoblasts, we found no evidence for the presence of disulphide-linked multimers of HLA-C complexes. These results show that most HLA-C molecules present at the trophoblast cell surface are in the conventional beta(2)m-associated conformation. These findings have implications regarding the stability of trophoblast HLA-C molecules and how they interact with receptors on decidual leucocytes during placentation.
authors.affiliation: Department of Pathology, Tennis Court Road, Cambridge, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Apps
authors.forename: Lucy
authors.initials: L
authors.lastname: Gardner
authors.forename: Sue E
authors.initials: SE
authors.lastname: Hiby
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Sharkey
authors.forename: Ashley
authors.initials: A
authors.lastname: Moffett
mesh_terms: D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006680:HLA Antigens / Q000737:chemistry / Q000276:immunology; D015236:HLA-C Antigens / Q000737:chemistry* / Q000276:immunology; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000276:immunology; D006801:Humans; D047468:Immunoprecipitation; D011247:Pregnancy; D011487:Protein Conformation; D011489:Protein Denaturation; D014327:Trophoblasts / Q000276:immunology*; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000378:metabolism
chemical_list: D006680:HLA Antigens; D015236:HLA-C Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; D001613:beta 2-Microglobulin