The Immune Response in Canine Atopy: hypersensitivity to house dust mites ['<i>Dermatophagoides</i> spp.']

The genetic and immunological basis of canine atopic dermatitis (CAD), a hypersensitivity disease to environmental allergens in dogs, was investigated. The evaluation of the clinical records of 434 dogs belonging to 92 litters related to dogs with CAD showed that the disease was greatly dependent upon genetic influences with a heritability of 0.49. Using a highly specific IgE detection reagent (FcƐRl alpha-chain) Dermatophagoides pteronyssinus (DP) -specific IgE was measured in the serum of normal and atopic dogs by ELISA. Dogs with CAD had significantly more DP-specific IgE than non- atopic dogs (pImmunoblotting revealed that the serum IgE response to DP in CAD was dominantly to three polypeptides with apparent molecular weights of 34, 63 and 89-95kDa. The 89- 95kDa polypeptide has been characterised as a mite chitinase. Cellular immune responses to DP extract were measured in normal and atopic dogs by measuring the antigen-specific proliferation of peripheral blood mononuclear cells. Atopic dogs showed greater proliferative responses to DP than normal dogs, although there was large individual variation. Dogs were immunised with DP extract to help identify the approximate molecular weights of allergens containing the dominant T-cell epitopes. The lymphocyte proliferative responses to DP polypeptides purified by SDS-PAGE were greatest to proteins of between 60 and 90kDa, similar in size to those reacting with serum IgE in dogs with CAD. Clinical and laboratory examination of dogs with allergic conjunctivitis showed that this condition was associated with CAD. Histopathological examination of conjunctival tissue often revealed signs of allergic response. However, IgE was not detected in the tears of enough affected dogs for it to be diagnostically useful. Family genetic studies and selective breeding programmes can significantly reduce the numbers of animals suffering from CAD. This study has identified antigens which should be used as the basis of improved CAD diagnostic and therapeutic reagents