Flow cytometry in impression cytology during keratoconjunctivitis sicca: effects of topical cyclosporin A on HLA DR expression

Purpose: Immune-based inflammation has been observed as a common mechanism of keratoconjunctivitis sicca (KCS). In KCS-affected eyes, up-regulated expression of HLA DR by conjunctival epithelial cells has been demonstrated in impression cytology (IC) specimens using a technique of flow cytometry. The purpose of this study was to monitor the effects of topical cyclosporin A on the expression of this marker over a 12-month period of treatment. Methods: Patients with moderate-to-severe KCS included in a large European multicenter clinical trial (Cyclosporin Dry Eye Study, Allergan, Irvine, CA) underwent collection of IC specimens at baseline, month 3, month 6, and month 12. They randomly received 0.05% or 0.1 % cyclosporin A or vehicle. Patients randomized to receive vehicle received 0.1 % cyclosporin A from month 6 onwards. Specimens were processed and analyzed in a masked manner by flow cytometry, using monoclonal antibodies directed to HLA DR. Results: We included 169 patients in this study. HLA DR expression, both in percentage of positive cells and level of expression, was highly significantly reduced after 0.05 % and 0.1 % cyclosporin A treatment at months 3, 6, and 12 compared with baseline values, whereas vehicle did not induce any change in HLA DR expression over time. The 0.05% and 0.1 % cyclosporin emulsions were significantly more effective than the vehicle in reducing HLA DR at months 3 and 6 (0.05%) and at month 6 (0.1 %). Conclusions: Topical cyclosporin A strikingly reduced HLA DR, whereas the vehicle, used as a control tear substitute, had almost no effect. This study confirms that cyclosporin A may be effective in reducing conjunctival inflammation in moderate-to-severe KCS and is consistent with clinical results in this indication.