Purpose: To determine the levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in tears of patients with dry eye syndrome.
Methods: IL-6 and TNF-alpha levels were measured by enzyme-linked immunosorbent assay in tear samples obtained from 18 patients with dry eye (8 patients with Sjögren syndrome and 10 patients with non-Sjögren syndrome) and 14 control subjects. The correlation between IL-6 and TNF-alpha levels and tear film and ocular surface parameters was analyzed. The relative expression of these cytokines was evaluated in conjunctival impression cytology and conjunctival biopsy specimens by using immunohistochemical staining.
Results: The mean levels of IL-6 and TNF-alpha were, respectively, 18.57 +/- 8.92 and 3.68 +/- 3.45 pg/mL in patients with dry eye and 3.59 +/- 3.38 (P < 0.01) and < 0.5 (P < 0.01) pg/mL in control subjects. IL-6 level was significantly increased in tears of patients with Sjögren syndrome compared with those with non-Sjögren syndrome (P < 0.01). IL-6 level correlated significantly with tear film breakup time (P = 0.04), Schirmer test (P < 0.01), tear clearance (P = 0.02), keratoepithelioplasty score (P < 0.01), and goblet cell density (P = 0.03), but not with corneal sensitivity (P = 0.08). There was no significant difference in TNF-alpha level between patients with non-Sjögren and Sjögren syndrome. TNF-alpha levels did not correlate with tear film and ocular surface parameters. Immunohistochemical staining showed positive staining for IL-6 in specimens from patients with dry eye, especially in specimens from patients with Sjögren syndrome.
Conclusion: IL-6 and TNF-alpha levels are elevated in tears of patients with dry eye syndrome. IL-6 level, but not TNF-alpha level, is associated with the severity of the disease and correlates with various tear film and ocular surface parameters.