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 cell analogs of human origin. Human IgE binds with exquisite species specificity to the high affinity IgE receptor (Fc epsilon RI) expressed on the surface of these cells. In rodents this receptor has been characterized as a tetrameric plasma membrane protein composed of an IgE-binding alpha chain, a beta chain and two disulfide-linked gamma chains. In order to establish a cell line expressing the alpha chain of human Fc epsilon RI which can be triggered with IgE from human patients and specific allergen, we transfected the cDNA coding for the human alpha subunit into rat basophilic leukemia cells. The resulting transfectants express the human alpha chain on the cell surface in the form of a hybrid complex associated with endogenous rat gamma chains. After sensitization with human IgE from mite-specific patients, the transfectant produces a calcium response upon incubation with allergen. The established cell line can be used as a model system to study the mechanism of mast cell triggering through IgE from allergic patients.