title: Prevention of murine lupus by an I-E alpha chain transgene: protective role of I-E alpha chain-derived peptides with a high affinity to I-Ab molecules.
abstract: The expression of a transgene encoding the I-E alpha chain prevents a lupus-like autoimmune syndrome in BXSB mice. However, it had not been elucidated whether the E alpha d transgene-mediated protective effect results from I-E expression or from the generation of I-E alpha chain-derived peptides (E alpha peptide) displaying high affinity for the I-Ab molecule. To address this question, two different BXSB lines expressing the transgene at low or high levels were crossed with lupus-prone MRL mice; this resulted in three types of (MRL x BXSB)F1 mice, differing in the expression levels of I-E molecules and of E alpha peptides presented by I-Ab molecules. Comparative analysis of these three (MRL x BXSB)F1 mice as well as several BXSB transgenic lines showed that the E alpha d transgene-mediated protection paralleled the expression levels of E alpha peptide presented by I-Ab molecules, but not of I-E molecules on B cells. In addition, use of transgenic and nontransgenic double bone marrow chimeras showed a selective activation of nontransgenic B cells during I-Ab-restricted T cell-dependent immune responses, while both transgenic and nontransgenic B cells were comparably activated during T cell-independent responses. These results favor a model of autoimmunity prevention based on competition for antigen presentation, in which excessive generation of E alpha peptides prevents, because of their high affinity to the I-A molecules, activation of potential autoreactive T and B cells.
authors.affiliation: Department of Pathology, Centre Medical Universitaire, University of Geneva, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Iwamoto
authors.forename: N
authors.initials: N
authors.lastname: Ibnou-Zekri
authors.forename: K
authors.initials: K
authors.lastname: Araki
authors.forename: S
authors.initials: S
authors.lastname: Izui
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003433:Crosses, Genetic; D005260:Female; D018628:Gene Dosage; D000949:Histocompatibility Antigens Class II / Q000737:chemistry* / Q000235:genetics* / Q000627:therapeutic use; D008180:Lupus Erythematosus, Systemic / Q000235:genetics* / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010047:Ovalbumin / Q000276:immunology; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D011485:Protein Binding / Q000276:immunology; D011828:Radiation Chimera / Q000276:immunology; D019076:Transgenes / Q000276:immunology*
chemical_list: D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D010455:Peptides; D010047:Ovalbumin