Cloning and expression of the extra-cellular part of the alpha chain of the equine high-affinity IgE receptor and its use in the detection of IgE

The high-affinity receptor for IgE (FcɛRI) plays a central role in IgE-mediated allergic reactions. Cross-linking of FcɛRI by IgE-antigen complexes results in the activation of mast cells and basophils and is thought to contribute to the immunopathology of Heaves, a chronic obstructive pulmonary disease of horses. Recombinant protein corresponding to the extra-cellular portion of the FcɛRI alpha subunit, cloned and sequenced previously [McAleese, S.M., Halliwell, R.E.W., Miller, H.R.P., 2000. Cloning and sequencing of the horse and sheep high-affinity IgE receptor α chain cDNA. Immunogenetics 51, 878–881], was expressed using both mammalian cells and insect cells. The yield of expressed protein was considerably greater using insect cells and the baculovirus expression system. The recombinant proteins differed in size between the two systems, presumably due to differences in the extent of glycosylation. However, recombinant protein from both cell systems bound equine IgE present in bronchoalveolar lavage fluid from horses with Heaves. These results suggest that the recombinant extra-cellular part of FcɛRI should be a useful tool with which to study equine IgE responses.