title: Mapping the site of interaction between murine IgE and its high affinity receptor with chimeric Ig.
abstract: We have investigated the interaction of mouse (m) IgE with its Fc epsilon RI on rat basophilic leukemia cells using a set of chimeric Ig that were constructed by exchanging homologous H chain C domains between human (hu) IgG1 and mIgE. Binding affinities were examined with equilibrium and kinetic measurements, and we found that epsilon/C gamma 3 (mIgE with C epsilon 4 replaced by C gamma 3) was indistinguishable from mIgE. The huIgG1 and the other chimeric Ig, which did not contain both C epsilon 2 and C epsilon 3, did not bind detectably to rat basophilic leukemia cells (Ka less than 10(6) M-1). The ability of these chimeric Ig to stimulate a cellular response (degranulation) in the presence of multivalent Ag was also tested. The epsilon/C gamma 3 was indistinguishable from mIgE in eliciting a high level of degranulation, whereas the other chimeric Ig stimulated no response even when they were preaggregated to enhance their binding avidity. These results demonstrate that C epsilon 4 may be replaced by C gamma 3 without affecting the binding and cell activating properties of mIgE. The lack of binding by the other chimeric Ig indicates that both C epsilon 2 and C epsilon 3 are necessary for the binding interaction.
authors: Department of Chemistry, Baker Laboratory, Cornell University, Ithaca, NY 14853.
authors: M
authors: M
authors: Weetall
authors: B
authors: B
authors: Shopes
authors: D
authors: D
authors: Holowka
authors: B
authors: B
authors: Baird
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism*; D001665:Binding Sites; D015550:Cell Degranulation; D006801:Humans; D007073:Immunoglobulin E / Q000235:genetics / Q000378:metabolism*; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism*; D015471:Leukemia, Basophilic, Acute / Q000276:immunology; D051379:Mice; D051381:Rats; D011961:Receptors, Fc / Q000378:metabolism*; D017455:Receptors, IgE; D011994:Recombinant Proteins / Q000378:metabolism*
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D007074:Immunoglobulin G; D011961:Receptors, Fc; D017455:Receptors, IgE; D011994:Recombinant Proteins; D007073:Immunoglobulin E