Immunoglobulin E‐specific allergens against leaf in serum of dogs with clinical features of grass leaf allergy

BackgroundGrass leaf has been suspected of causing immunoglobulin (Ig)E‐mediated immediate hypersensitivity reactions in humans and dogs. However, most studies in this area are case‐control studies without in vitro data showing the involvement of IgE in the reaction. Laboratory studies have demonstrated the reactivity to a 50–55 kDa protein with clinical signs immediately after contact with grass leaf material. The clinical findings of dogs with atopic‐like dermatitis immediately after contact with grass leaf material suggest the involvement of grass leaves as the allergen source.ObjectivesThis study was designed to test the IgE‐reactivity of grass leaf proteins in dogs with clinical signs and positive scratch test results against grass leaf material.Materials and MethodsThe serum of 41 patients with a history of allergy and suspected to grass leaf material was immunoblotted against grass leaf extracts from five suspected grass species. The IgE‐positive blots were separated with 2D gel electrophoresis and analysed with mass spectrometry (MS). Commercially supplied proteins were used to validate immunoblot activity.ResultsThe serum of 25 dogs diagnosed with grass dermatitis had positive IgE‐specific immunoblot against one or more grass leaf extracts. The MS data indicated a reactive band at 55 kDa to be beta‐amylase or RuBisCO (ribulose‐1,5‐bisphosphate carboxylase/oxygenase) large subunit (RbLS). All tested dog sera showed IgE‐reactivity with beta‐amylase and some with RbLS.Conclusions and Clinical RelevanceCanines with clinical signs of grass‐related dermatitis had IgE‐reactivity against grass leaf proteins. Serum IgE‐reactivity to beta‐amylase and RuBisCO large subunit may indicate that these proteins act as allergens, possibly causing pruritus and skin lesions.