title: Alpha-actinin-binding antibodies in relation to systemic lupus erythematosus and lupus nephritis.
abstract: This study investigated the overall clinical impact of anti-alpha-actinin antibodies in patients with pre-selected autoimmune diseases and in a random group of anti-nuclear antibody (ANA)-positive individuals. The relation of anti-alpha-actinin antibodies with lupus nephritis and anti-double-stranded DNA (anti-dsDNA) antibodies represented a particular focus for the study. Using a cross-sectional design, the presence of antibodies to alpha-actinin was studied in selected groups, classified according to the relevant American College of Rheumatology classification criteria for systemic lupus erythematosus (SLE) (n = 99), rheumatoid arthritis (RA) (n = 68), Wegener's granulomatosis (WG) (n = 85), and fibromyalgia (FM) (n = 29), and in a random group of ANA-positive individuals (n = 142). Renal disease was defined as (increased) proteinuria with haematuria or presence of cellular casts. Sera from SLE, RA, and Sjøgren's syndrome (SS) patients had significantly higher levels of anti-alpha-actinin antibodies than the other patient groups. Using the geometric mean (+/- 2 standard deviations) in FM patients as the upper cutoff, 20% of SLE patients, 12% of RA patients, 4% of SS patients, and none of the WG patients were positive for anti-alpha-actinin antibodies. Within the SLE cohort, anti-alpha-actinin antibody levels were higher in patients with renal flares (p = 0.02) and correlated independently with anti-dsDNA antibody levels by enzyme-linked immunosorbent assay (p < 0.007) but not with other disease features. In the random ANA group, 14 individuals had anti-alpha-actinin antibodies. Of these, 36% had SLE, while 64% suffered from other, mostly autoimmune, disorders. Antibodies binding to alpha-actinin were detected in 20% of SLE patients but were not specific for SLE. They correlate with anti-dsDNA antibody levels, implying in vitro cross-reactivity of anti-dsDNA antibodies, which may explain the observed association with renal disease in SLE.
authors.affiliation: Department of Rheumatology, Institute of Clinical Medicine, University of Tromsø, Breivika, N-9037 Tromsø, Norway. andrea.becker-merok@unn.no
authors.forename: Andrea
authors.initials: A
authors.lastname: Becker-Merok
authors.forename: Manar
authors.initials: M
authors.lastname: Kalaaji
authors.forename: Kaia
authors.initials: K
authors.lastname: Haugbro
authors.forename: Cathrin
authors.initials: C
authors.lastname: Nikolaisen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Nilsen
authors.forename: Ole Petter
authors.initials: OP
authors.lastname: Rekvig
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Nossent
mesh_terms: D000185:Actinin / Q000276:immunology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000974:Antibodies, Antinuclear / Q000097:blood; D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000097:blood / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D003429:Cross Reactions; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000276:immunology; D008181:Lupus Nephritis / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged
chemical_list: D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D015415:Biomarkers; D000185:Actinin