title: Semiquantitative measurement of aquaporin-4 antibodies as a possible surrogate marker of neuromyelitis optica spectrum disorders with systemic autoimmune diseases.
abstract: OBJECTIVE
  To assess the association between serum aquaporin-4 (AQP4) autoantibodies and neuromyelitis optica spectrum disorders (NMOSDs) associated with systemic autoimmune diseases.
  
  
  METHODS
  We retrospectively studied 626 hospitalized patients with systemic lupus erythematosus (SLE) or Sjögren's syndrome (SS). We collected serum samples from those patients with suspected NMOSDs (i.e., myelitis or optic neuritis) at the time of onset and thereafter. AQP4 antibodies were measured by a cell-based indirect immunofluorescence assay using AQP4-transfected HEK-293 cells in a semi-quantitative manner.
  
  
  RESULTS
  Sera from 6 patients with suspected NMOSDs and SLE (n = 3) or SS (n = 3) were evaluated. Among these, 2 patients' sera samples, i.e., 1 with SLE and 1 with SS, were positive for AQP4 antibodies. There was an inverse relationship between disease amelioration and antibody titer in one NMOSD patient, whereas the antibody titer remained high in the other NMOSD patient, whose clinical manifestations of NMOSDs did not improve despite intensive immunosuppressive treatments.
  
  
  CONCLUSIONS
  These results indicate that serum AQP4 antibodies are present in some SLE/SS patients with myelitis/optic neuritis and might be associated with clinical outcomes. The semi-quantitative measurement of the AQP4 antibody might be a possible surrogate marker in patients with NMOSDs associated with systemic autoimmune diseases.
authors.affiliation: Institute of Rheumatology, Tokyo Women's Medical University, 10-22 Kawada-cho, Shinjuku-ku, Tokyo 162-0054, Japan. katsumata@ior.twmu.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Katsumata
authors.forename: Izumi
authors.initials: I
authors.lastname: Kawachi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: Takahisa
authors.initials: T
authors.lastname: Gono
authors.forename: Hisae
authors.initials: H
authors.lastname: Ichida
authors.forename: Masako
authors.initials: M
authors.lastname: Hara
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamanaka
mesh_terms: D000328:Adult; D051401:Aquaporin 4 / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001327:Autoimmune Diseases; D015415:Biomarkers; D016022:Case-Control Studies; D003520:Cyclophosphamide / Q000627:therapeutic use; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D057809:HEK293 Cells; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007275:Injections, Intravenous; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology*; D008875:Middle Aged; D009471:Neuromyelitis Optica / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology*; D012189:Retrospective Studies; D012595:Scleroderma, Systemic / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: C496030:AQP4 protein, human; D051401:Aquaporin 4; D001323:Autoantibodies; D015415:Biomarkers; D005938:Glucocorticoids; D007166:Immunosuppressive Agents; D003520:Cyclophosphamide