AbstractObjectivesThe purpose of this study was to characterize the expression of interleukin‐11 (IL‐11), a cytokine with anti‐inflammatory, cytoprotective, and immune‐modulating characteristics, in the canine eye.ProceduresNormal canine eyes were collected from clinically healthy dogs that had been euthanized for reasons unrelated to this study. The distribution of IL‐11 expression in the different ocular layers was evaluated by immunofluorescence (eight eyes). Expression levels were quantified (based on fluorescence intensity) using pixel density analysis. Primary cell cultures were derived from all three corneal cell layers. IL‐11 mRNA expression was assessed in these cultures using quantitative RT‐PCR before and after treatment with TGF‐β1, a known inducer of IL‐11 expression. IL‐11 protein expression was also assessed in the media of these cells by Western blot analysis.ResultsIL‐11 protein was detected in the corneal epithelium, keratocytes, and the corneal endothelium of the normal canine eyes examined using immunofluorescence. Baseline IL‐11 mRNA expression was noted in the corneal epithelium, fibroblasts, and endothelium using quantitative RT‐PCR. Treatment of canine corneal cell lines with TGF‐β1 resulted in statistically significant increases in IL‐11 expression in the corneal epithelium, endothelial and fibroblast cell lines with strongest induction noted in the fibroblasts and endothelium.ConclusionThis is the first description of IL‐11 expression in the canine eye. The protein and mRNA appear to be constitutively present throughout all layers of the cornea and are increased by TGF‐β1, a cytokine important in ocular inflammation and disease.