These double mutant mice express the human Fc fragment of IgE, high affinity I, receptor for; alpha polypeptide, (FCER1A), under the control of the human FCER1A promoter and carry the Fcer1atm1Knt targeted mutation. Mice that are hemizygous for the transgene and homozygous for the targeted mutation express a functioning chimeric receptor complex in which the human alpha-chain associates with the mouse beta- and gamma- chains. Transgene expression is detected on bone marrow derived cultured mast cells (BMMC), mast cells, basophils, monocytes, eosinophils, and epidermal Langerhans cells by FACS, hIgE binding and Western blot analysis and mimics both the human FCER1A expression and cell specificity pattern. The humanized receptor is estimated to be expressed approximately 3 to 5 fold higher than the endogenous mouse receptor. The double mutant mice respond to experimental induction of anaphylaxis and are more sensitive to 2,4,6-tri-nitrobenzenesulfonic acid (TNBS)-induced colitis. These mutant mice exhibit increased levels of IL4 in the colon, enhanced intestinal permeability and modified fecal bacterial flora composition. This mutant mouse strain may be useful in studies of allergic response, anaphylaxis, hypersensitive immune response, and inflammatory bowel disease.
