title: Autoimmunity to a 28-30 kD cell membrane DNA binding protein: occurrence in selected sera from patients with SLE and mixed connective tissue disease (MCTD).
abstract: Previous experiments have established the presence of a 30-kD DNA binding protein on the surface of human leukocytes. Herein we report that selected sera from patients with systemic lupus erythematosus (SLE) and MCTD are reactive with a 28-30 kD protein on immunoblots of peripheral blood mononuclear cells (PBMC) cell membrane preparations; the reactivity is abolished by prior incubation of the blot with DNA. Antibodies eluted from the 28-30 kD strip inhibited the binding of 3H. DNA to human PBMC. An immunomatrix of 28-30 kD reactive immunoglobulins was able to extract a 29-kD DNA binding protein from a PBMC cell membrane preparation. Flow cytometry experiments confirmed the cell surface IgG reactivity of sera with T lymphocytes. Additional experiments indicated that cell surface IgG binding was not due to antibodies binding to cell surface DNA, DNA anti-DNA immune complexes reacting with a DNA binding protein, anti-histone antibodies or anti-Sm antibodies. It is hypothesized that this autoimmune response could be one component of an idiotypic network involving anti-DNA antibodies.
authors.affiliation: Department of Medicine, Oregon Health Sciences University, Portland 97201.
authors.forename: R M
authors.initials: RM
authors.lastname: Bennett
authors.forename: K A
authors.initials: KA
authors.lastname: Cornell
authors.forename: M J
authors.initials: MJ
authors.lastname: Merritt
authors.forename: A C
authors.initials: AC
authors.lastname: Bakke
authors.forename: P H
authors.initials: PH
authors.lastname: Hsu
authors.forename: S H
authors.initials: SH
authors.lastname: Hefeneider
mesh_terms: D001323:Autoantibodies / Q000032:analysis; D015551:Autoimmunity; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000276:immunology*; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008947:Mixed Connective Tissue Disease / Q000276:immunology*; D013601:T-Lymphocytes / Q000166:cytology
chemical_list: D001323:Autoantibodies; D004268:DNA-Binding Proteins