Abstract
Purpose: :
To determine levels of interleukin–6 (IL–6) and tumor necrosis factor α (TNF–α) in tears of patients with dry eye syndrome and analyze the correlation between levels of these cytokines and tear film and ocular surface parameters.
Methods: :
IL–6 and TNF–α levels were measured by enzyme–linked immunosorbent assay in tear samples obtained from 18 dry eye patients (8 patients with Sjögren’s syndrome and 10 patients with non–Sjögren’s syndrome) and 14 control subjects. The correlation between IL–6 and TNF–α levels and tear film and ocular surface parameters including corneal sensitivity, tear film break up time (BUT), Schirmer test, tear clearance, keratoepitheliopathy score, and conjunctival goblet cell density were analyzed. The relative expression of these cytokines was evaluated in conjunctival impression cytology and conjunctival biopsy specimens using immunohistochemical staining.
Results: :
The mean concentrations of IL–6 and TNF–α were 18.57 ± 8.92 and 3.59 ± 3.38 pg/ml in dry eye patients and 3.68 ± 3.45 (P<0.01) and < 0.5 (P<0.01) pg/ml in control subjects, respectively. IL–6 level was significantly increased in tears of patients with Sjögren’s syndrome (P<0.01) compared with non–Sjögren’s syndrome patients. IL–6 level correlated significantly with tear film BUT (R=–0.50, P=0.04), Schirmer test (R=–0.79, P<0.01), tear clearance (R=0.53, P=0.02), keratoepitheliopathy score (R=0.72, P<0.01), and goblet cell density (R=–0.51, P=0.03) except corneal sensitivity (R=–0.34, P=0.08). However, there was no significant difference in TNF–α level between Sjögren’s and non–Sjögren’s syndrome patients. TNF–α level did not correlate with tear film and ocular surface parameters. Immunohistochemical staining showed positive staining for IL–6 in specimens from dry eye patients, especially in specimens form Sjögren’s syndrome patients.
Conclusions: :
IL–6 and TNF–α levels are elevated in tears of patients with dry eye syndrome. IL–6 level, not TNF–α level, is associated with severity of the disease and also correlated with various tear film and ocular surface parameters.
Keywords: cornea: tears/tear film/dry eye • cytokines/chemokines