Analysis of Inflammatory Cytokines in the Tears of Dry Eye Patients

Purpose: To determine the levels of 8 important cytokines and 1 chemokine in tears of patients with dry eye disease. Methods: Tear samples were collected from 7 patients with dry eye disease and 7 healthy volunteers, and impression cytology samples were collected from 3 of the dry eye patients and 3 of the normal controls. Tears were analyzed for the presence of 8 cytokines [interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-1 beta] and 1 chemokine (IL-8). The cytokines and chemokine in each tear sample were measured using Invitrogen's Multiplex Bead Immunoassays. The impression cytology samples were analyzed for IL-1 beta, IL-6, IL-8, and TNF-alpha mRNA expression using real-time reverse transcriptase polymerase chain reaction anlaysis. Results: All cytokines and the chemokine measured were significantly increased in the tears of dry eye patients as compared to normal controls. mRNA of all four markers was increased, and the fold increase correlated well with the fold increase of the cytokine concentration found in the tear samples. Conclusion: Tears from dry eye patients contain significantly increased concentrations of cytokines that show correlation to severity of the disease. The upregulation of their respective genes in the conjunctiva suggests that the concentration increase is not the result of evaporative effects, but of overproduction. These findings suggest that cytokines may play an important role in dry eye disease and topical cytokine modulators may be explored as a therapeutic approach to dry eye disease.