title: Qa-1, a nonclassical class I histocompatibility molecule with roles in innate and adaptive immunity.
abstract: Qa-1, a nonclassical class I histocompatibility molecule expressed in mice, predominantly assembles with a single nonameric peptide, Qdm, derived from the signal sequence of certain class Ia molecules. The Qa-1/Qdm complex is the primary ligand for CD94/NKG2A inhibitory receptors expressed on a major fraction of natural killer (NK) cells. Cells become susceptible to killing by NK cells under conditions where surface expression of the Qa-1/Qdm inhibitory ligand is reduced. The CD94/NKG2 "missing-self" recognition system serves as mechanism for removing cells that have abnormalities in the intracellular machinery required for assembly and expression of class I-peptides complexes, as a consequence of viral infection, for example. Despite its highly focused peptide-binding specificity, Qa-1 also has a capacity to act as an antigen-presentation molecule for CD8+ T cells. It appears that a small subpopulation of these T cells undergoes positive selection by interaction with Qa-1 in the thymus, and they maintain their specificity for Qa-1 after maturation. The role of these unusual T cells in adaptive immune responses remains to be defined.
authors.affiliation: Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA. pjensen@emory.edu
authors.forename: Peter E
authors.initials: PE
authors.lastname: Jensen
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Sullivan
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Reed-Loisel
authors.forename: Dominique A
authors.initials: DA
authors.lastname: Weber
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000276:immunology; D006680:HLA Antigens / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000502:physiology*; D007110:Immunity, Active; D007113:Immunity, Innate; D007328:Insulin / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D037181:Lectins, C-Type / Q000276:immunology; D051379:Mice; D055654:NK Cell Lectin-Like Receptor Subfamily C; D051920:NK Cell Lectin-Like Receptor Subfamily D; D011971:Receptors, Immunologic / Q000276:immunology; D055607:Receptors, Natural Killer Cell; D013601:T-Lymphocytes / Q000276:immunology; D000097625:HLA-E Antigens
chemical_list: D015703:Antigens, CD; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D007328:Insulin; D037181:Lectins, C-Type; D055654:NK Cell Lectin-Like Receptor Subfamily C; D051920:NK Cell Lectin-Like Receptor Subfamily D; D011971:Receptors, Immunologic; D055607:Receptors, Natural Killer Cell; D000097625:HLA-E Antigens; C527057:Klrc1 protein, mouse; C497870:Klrd1 protein, mouse; C032907:Q surface antigens