EXPRESSION OF THE ALPHA-CHAIN OF HUMAN FC-EPSILON-RI IN TRANSFECTED RAT BASOPHILIC LEUKEMIA-CELLS - FUNCTIONAL ACTIVATION AFTER SENSITIZATION WITH HUMAN MITE-SPECIFIC IGE

The actual dilemma in studying the binding and triggering capacity of IgE from allergic patients is the lack of cultured basophils or mast c ell analogs of human origin. Human IgE binds with exquisite species sp ecificity to the high affinity IgE receptor (FcepsilonRI) expressed on the surface of these cells. In rodents this receptor has been charact erized as a tetrameric plasma membrane protein composed of an IgE-bind ing alpha chain, a beta chain and two disulfide-linked gamma chains. I n order to establish a cell line expressing the alpha chain of human F cepsilonRI which can be triggered with IgE from human patients and spe cific allergen, we transfected the cDNA coding for the human alpha sub unit into rat basophilic leukemia cells. The resulting transfectants e xpress the human alpha chain on the cell surface in the form of a hybr id complex associated with endogenous rat gamma chains. After sensitiz ation with human IgE from mite-specific patients, the transfectant pro duces a calcium response upon incubation with allergen. The establishe d cell line can be used as a model system to study the mechanism of ma st cell triggering through IgE from allergic patients.