title: Antiperinuclear factor of the IgA isotype in active rheumatoid arthritis.
abstract: OBJECTIVE
  For rheumatoid arthritis (RA), antiperinuclear factor (APF) is as efficient a marker as rheumatoid factor (RF). However, the prevalence and significance of APF of the IgA isotype in active RA, as well as its correlation with RF-IgA, have not been determined. Our goal was to obtain information on these points.
  
  
  METHODS
  APF-IgA were screened in 80 sera from patients with active RA, prospectively and consecutively selected over an 8-month period. Sera from 22 patients with Sjögren's syndrome and 50 with lupus were also studied retrospectively for APF-IgG and IgA.
  
  
  RESULTS
  APF-IgA were found at a 1:10 dilution or above in 31 RA sera (39%), which were all positive for APF-IgG as well at higher titers. In the 64 sera positive for APF no correlations were found between APF-IgA and IgA or immune complexes-IgA, latex, the Rose-Waaler test and RF-IgA. Conversely, an association of APF-IgA was found with both APF-IgG (p < 0.0001) and anti-stratum corneum of rat esophagus (ASC)-IgG (p < 0.0001). APF-IgA, though correlated with the presence of secondary sicca syndrome in RA (p = 0.0023), was not more frequent (5/22) in primary Sjögren's sera.
  
  
  CONCLUSIONS
  RF-IgA and APF-IgA are not correlated. Despite its localization in the mucosae, the target antigen for APF elicit fewer IgA antibodies in RA than does the RF target.
authors.affiliation: Department of Rheumatology, Nantes University Medical School Hospital, France.
authors.forename: J M
authors.initials: JM
authors.lastname: Berthelot
authors.forename: B
authors.initials: B
authors.lastname: Bendaoud
authors.forename: Y
authors.initials: Y
authors.lastname: Maugars
authors.forename: M
authors.initials: M
authors.lastname: Audrain
authors.forename: A
authors.initials: A
authors.lastname: Prost
authors.forename: P
authors.initials: P
authors.lastname: Youinou
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000974:Antibodies, Antinuclear / Q000276:immunology*; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D005260:Female; D000091344:Filaggrin Proteins; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007381:Intermediate Filament Proteins / Q000032:analysis; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000473:pathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D051381:Rats; D017208:Rats, Wistar; D012189:Retrospective Studies; D012217:Rheumatoid Factor / Q000276:immunology; D012859:Sjogren's Syndrome / Q000378:metabolism
chemical_list: D000974:Antibodies, Antinuclear; D015415:Biomarkers; D000091344:Filaggrin Proteins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007381:Intermediate Filament Proteins; C030902:antiperinuclear factor; D012217:Rheumatoid Factor