Survey of cytokines on ocular surfaces of atopic dogs by multiplex analysis using two sampling methods – a pilot study

Abstract

Background: Conjunctivitis in atopic dogs has already been described yet is rarely observed, and likely underdiagnosed in practice. Objectives: To assay various cytokines in tears and conjunctivae from atopic and normal dogs, and to compare canine atopic dermatitis-associated conjunctivitis with controls. Animals: Ten atopic and ten normal client-owned dogs. Methods and materials: Ocular surfaces were sampled bilaterally in a prospective study, using two different methods. Tear samples were obtained with a sterile swab previously moistened with saline solution (method A). Conjunctival impressions were obtained with a conjunctival impression device (method B). For each sample, the concentrations of a panel of 13 cytokines were measured by multiplex analyses. CADESI-4, pruritus (PS) and conjunctival (CS) scores were determined. Results: Among the measured cytokines, only granulocyte-macrophage colony-stimulating factor (GM-CSF), keratinocyte-derived chemokine (KC)-like and interleukin (IL)-8 were above the limit of quantification in most samples. Absolute amounts of each cytokine were always higher in samples obtained with method A than with method B. GM-CSF amounts were lower in atopic dogs (method A, P=0.02; method B, P=0.0005). KC levels were higher in atopic dogs, yet the differences were not significant. IL-8 amounts were higher in atopic dogs (method A, P=0.0003; method B, P=0.006). Conclusions and clinical relevance: Regardless of the method, these preliminary results suggest an overexpression of IL-8 in conjunctivae and tears of atopic dogs despite subtle conjunctival symptoms. As IL-8 is commonly found in many inflammatory conditions, further studies are needed to determine its specificity in atopic conjunctivitis.