Flea allergy dermatitis in the cat: Establishment of a functional in vitro test

Abstract

The purpose of this study was to develop a reliable and sensitive allergy test in the cat: The functional in vitro test (FIT) is monitoring exclusively those antibodies sensitizing basophiles and mastcells known as the prime initiators of type I allergies. By means of their Fc-receptors they accumulate antibodies of selected isotypes on their surface. Depending on their specificity these antibodies may bind the “fitting” antigens as bridging “allergens” causing the release of various mediators and, thus, the induction of type I allergy reactions. Histamine is one of these mediators and the only one being stored in considerable amounts in basophils and mastcells exclusively. The FIT was applied to blood specimens of a population of flea-infested laboratory cats. Individual blood samples were washed and divided into subunits. Treatments comprising spontaneous, physical, antibody and antigen mediated histamine release were applied. For antigen induced release the flea antigen was titrated at final concentrations between 1 and 1 * 10^-6 μg/ml. The amount of released histamine was quantified by a radio immuno assay (RIA). Blood samples from individual cats showed interdividual variations of histamine contents as observed in humans and mice. The allergen preparation of Ctenocephalides spp. proved to be free of unspecific triggering of feline basophils. In the concentrations tested it caused dose dependent and individually very different reactions. Thus, this functional in vitro test system might provide a sensitive and reliable monitoring for type I allergies in the cat. It still requires further investigations regarding evaluation of allergen released histamine in order to obtain clinically relevant results.