title: Association of IL-21 cytokine with severity of primary Sjögren syndrome dry eye.
abstract: OBJECTIVE
  IL-21 plays an important role in primary Sjögren syndrome (SS) pathogenesis. The purpose of this study was to evaluate IL-21 expression in tears and the conjunctiva and to analyze the impact of IL-21 on primary SS dry eyes.
  
  
  METHODS
  Eighty subjects were enrolled in this study: 30 patients with primary SS dry eye (30 eyes); 30 patients with non-SS dry eye (30 eyes), and 20 normal controls. Tear IL-21 levels were measured by flow cytometry, and IL-21 gene expression in the conjunctiva from impression cytology was evaluated by quantitative polymerase chain reaction. Ocular Surface Disease Index, tear film breakup time, Schirmer I test, and ocular surface staining scores were obtained for all patients.
  
  
  RESULTS
  Primary SS dry eyes had significantly higher tear IL-21 levels than non-SS dry eyes and normal controls (P < 0.01). In addition, IL-21 gene expression in the conjunctiva was also higher in primary SS dry eyes than in non-SS dry eyes and normal controls (P < 0.01). However, there were no significant differences in IL-21 expression in tears and the conjunctiva between non-SS dry eyes and controls. The tear IL-21 level was significantly correlated with ocular surface stain scores (r = 0.54, P < 0.01) and Schirmer I test values (r = -0.23, P < 0.05) in primary SS dry eyes.
  
  
  CONCLUSIONS
  Our findings suggest that severity of primary SS dry eye is associated with IL-21.
authors.affiliation: *Department of Ophthalmology and Visual Science, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea; †Catholic Institute for Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea; ‡Northfield Mount Hermon School, MA; and §Division of Rheumatology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Sung A
authors.initials: SA
authors.lastname: Lim
authors.forename: Doo Hyun
authors.initials: DH
authors.lastname: Nam
authors.forename: Jee Hye
authors.initials: JH
authors.lastname: Lee
authors.forename: Seung-Ki
authors.initials: SK
authors.lastname: Kwok
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Park
authors.forename: So-Hyang
authors.initials: SH
authors.lastname: Chung
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003228:Conjunctiva / Q000378:metabolism / Q000473:pathology; D015352:Dry Eye Syndromes / Q000209:etiology / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007378:Interleukins / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012720:Severity of Illness Index; D012859:Sjogren's Syndrome / Q000378:metabolism*; D013666:Tears / Q000378:metabolism; D000098546:Interleukin-21
chemical_list: D007378:Interleukins; D000098546:Interleukin-21