Expression of the Alpha Chain of Human FcεRI in Transfected Rat Basophilic Leukemia Cells: Functional Activation after Sensitization with Human Mite-Specific IgE

Abstract

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 (FcεRI) 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 α chain, a β chain and two disulfide-linked γ chains. In order to establish a cell line expressing the α chain of human FcεRI which can be triggered with IgE from human patients and specific allergen, we transfected the cDNA coding for the human α subunit into rat basophilic leukemia cells. The resulting transfectants express the human α chain on the cell surface in the form of a hybrid complex associated with endogenous rat γ 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.

Alternative Endocytic Pathway for Immunoglobulin A Fc Receptors (CD89) Depends on the Lack of FcRγ Association and Protects against Degradation of Bound Ligand

“…The percentage of specifically precipitated counts was calculated for each Ab after subtraction of nonspecific counts obtained using either irrelevant IgG1-coupled beads or lysates that had been preincubated with a 100-fold excess of unlabeled antiFc␣R mAb (nonspecific counts were always Ͻ3%). For RBL transfectants, 3 l of polyclonal rabbit anti-␥ chain antiserum plus protein A-coupled beads were used to coprecipitate both rat and human ␥ chains (49). Normal rabbit serum was used to determine background precipitation.…”

Transmembrane Sequences Are Determinants of Immunoreceptor Signaling

“…All of these receptors contain the EC region of human Fc⑀RI␣, allowing selective sensitization with huIgE in the absence of sensitization of endogenous Fc⑀RI (26), and they also contain the CT segment of the TCR subunit, which has three ITAM sequences (2) (Fig. 1A).…”

Evaluation of an in vitro Mast Cell Degranulation Test in the Context of Food Allergy to Wheat

“…The transfection of cDNAs coding for the α-subunit of the human FcεRI into a rat basophilic leukemia (RBL) mast cell line is a means to obtain suitable effectors that can be triggered with human serum IgE and specific allergen [11,21,22,23,24,25]. …”