title: Quantitative assays for anti-aquaporin-4 antibody with subclass analysis in neuromyelitis optica.
abstract: BACKGROUND
  To clarify the clinical relevance of anti-aquaporin-4 (anti-AQP4) antibody titers and immunoglobulin (IgG) subclass.
  
  
  METHODS
  Using a bridging enzyme-linked immunosorbent assay (ELISA), a flow cytometric assay (FCMA) and an immunofluorescence assay (IFA) for anti-AQP4 antibodies, sera from 142 patients with multiple sclerosis (MS) as defined by the McDonald criteria (2005), 29 with neuromyelitis optica (NMO) who fulfilled the 1999 criteria, 19 with recurrent and/or longitudinally extensive myelitis (RM/LM), 86 with other non-inflammatory neurological diseases (OND) and 28 healthy controls (HC) were studied.
  
  
  RESULTS
  Anti-AQP4 antibody positivity rates by IFA, FCMA, and ELISA were 41.4%, 51.7% and 48.3%, respectively, in NMO (1999) patients, and 0% in the OND and HC groups. Twenty-six MS patients (18.3%) were positive for the antibody; 17 met the 2006 NMO criteria, including positivity for anti-AQP4 antibody, and five had longitudinally extensive myelitis (LM). Among the cases with anti-AQP4 antibody detected by FCMA, IgG1, 2, 3, and 4 anti-AQP4 antibodies were found in 97.8%, 37.0%, 6.5% and 6.5% respectively. There was no association of either antibody positivity or level of anti-AQP4 antibody IgG subclasses with clinical parameters after adjustment of p values for multiple comparisons.
  
  
  CONCLUSIONS
  FCMA and bridging ELISA are useful for detecting and quantifying anti-AQP4 antibodies.
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Isobe
authors.forename: Tomomi
authors.initials: T
authors.lastname: Yonekawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsushita
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kawano
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Masaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yoshimura
authors.forename: Jakub
authors.initials: J
authors.lastname: Fichna
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.forename: Jadwiga
authors.initials: J
authors.lastname: Furmaniak
authors.forename: Bernard Rees
authors.initials: BR
authors.lastname: Smith
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Kira
mesh_terms: D051401:Aquaporin 4 / Q000235:genetics / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood* / Q000145:classification; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D057809:HEK293 Cells; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D009471:Neuromyelitis Optica / Q000097:blood / Q000276:immunology*; D011237:Predictive Value of Tests; D011993:Recombinant Fusion Proteins / Q000276:immunology; D012680:Sensitivity and Specificity; D014162:Transfection
chemical_list: C496030:AQP4 protein, human; D051401:Aquaporin 4; D001323:Autoantibodies; D015415:Biomarkers; D007074:Immunoglobulin G; D011993:Recombinant Fusion Proteins