Abstract
The binding of immunoglobulin E (IgE) to its high-affinity receptor (Fc epsilon RI) is the central protein interaction in IgE-mediated allergic reactions. The cross-linking of the IgE/Fc epsilon RI complex, through cognate allergens, on the surface of mast cells and basophil cells results in mediator release, and thus leads to the symptoms of type I hypersensitivity responses in mammals. To develop a baseline value for subsequent equine anti-allergy drug and vaccine research, the interaction of equine IgE with its high-affinity Fc epsilon RI receptor was investigated following the cloning and expression of equine IgE with specificity for NIP-HSA (4-hydroxy-5-iodo-3-nitrophenylacetic acid conjugated to human serum albumin). Receptor recognition and effector functions were assessed in Rat Basophil Leukemia (RBL-2H3.1) cells transfected with the alpha chain of equine and canine Fc epsilon RI. Results obtained showed that the equine Fc epsilon RI receptor recognizes both equine and canine IgE and supports similar beta-hexosaminidase release levels from RBL cells transfected with equine Fc epsilon RI, peaking at 36.68% at 100 ng ml(-1) antigen and 32.00% at 100 ng ml(-1) antigen respectively. Furthermore, the binding kinetics of the equine IgE to the equine Fc epsilon RI receptor and the canine IgE to the same receptor was measured to be K-A = 6.33 x 10(9) M-1 and K-A = 1.84 x 10(9) M-1 respectively. This research established basic reagents and vitro assay systems to underpin the development of rational therapeutic intervention strategies to combat equine allergic manifestations. (C) 2013 Elsevier B.V. All rights reserved.