title: Characterization of an HLA-DR4-restricted T cell clone recognizing a protein moiety of small nuclear ribonucleoproteins (UsnRNP).
abstract: In sera of patients with mixed connective tissue disease (MCTD, Sharp Syndrome) high titres of IgG autoantibodies to U1snRNP-specific proteins are found. The isolated occurrence of these autoantibodies is highly associated with the HLA-DR4 haplotype. snRNP-specific T cells are supposed to be involved in this autoantibody production. To address this question we cultured mononuclear cells from MCTD patients and healthy donors with a highly purified UsnRNP preparation from HeLa cells using bulk or limiting dilution cultures. Secondary responses to snRNP were detected only rarely with T cell lines from two patients and two controls, and turned out to be unstable during further expansion. One T cell line derived from a healthy individual retained its snRNP reactivity upon limiting dilution cloning and could be characterized in detail. The CD4+ T cell clone recognized native snRNP particles presented by monocytes in an HLA-DR4 (B1*0401)-restricted manner. Separation of the protein and RNA moieties of snRNP particles revealed that the T cell clone responded specifically to the protein fraction, but not to RNA and diverse control antigens. Sequencing of the T cell receptor alpha and beta chain cDNAs revealed that the clone used the V alpha 14.2 and V beta 14 elements. Upon antigen-specific and mitogenic stimulation the T cell clone showed a Th1-specific cytokine pattern, and did not provide helper activity for in vitro immunoglobulin production. This study demonstrate the presence of self-reactive snRNP-specific T cells in a healthy donor. The T cell clone may not represent a helper T cell for the formation of U1snRNP-specific autoantibodies.
authors.affiliation: Abt. Rheumatologie und Klinische Immunologie, Medizinische Klinik, Freiburg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Wolff-Vorbeck
authors.forename: W
authors.initials: W
authors.lastname: Hackl
authors.forename: S
authors.initials: S
authors.lastname: Fenning
authors.forename: U
authors.initials: U
authors.lastname: Krawinkel
authors.forename: R
authors.initials: R
authors.lastname: Lührmann
authors.forename: H H
authors.initials: HH
authors.lastname: Peter
authors.forename: M
authors.initials: M
authors.lastname: Schlesier
mesh_terms: D000595:Amino Acid Sequence; D000938:Antigen-Presenting Cells; D015551:Autoimmunity / Q000276:immunology*; D001483:Base Sequence; D002999:Clone Cells / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis; D015804:HLA-DR4 Antigen / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics; D017411:Ribonucleoproteins, Small Nuclear / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D016207:Cytokines; D015804:HLA-DR4 Antigen; D016693:Receptors, Antigen, T-Cell, alpha-beta; D017411:Ribonucleoproteins, Small Nuclear