Inhibition of IgE Activity to Bind its High Affinity Receptor (FcεRIα) by Mouse Anti-IgE Cε3∼4 Monoclonal Antibody (QME5)

Using computer-guided homology modeling method, the 3-D structure of the Fv fragment of a functional anti-IgE antibody (MAE11) was constructed and the spatial structure of E24-MAE11 complex was modeled based on the crystal structure of IgE-Fc (abbr. E24) and molecular docking method. Then the identified epitope of IgE was determined theoretically, which showed the key role of IgE-Cɛ3 in interacting with both FcɛRIα and MAE11. By normal protocols, we immunized mice with purified protein E34 and screened six anti-E34 monoclonal antibodies. Purified antibodies could identify E34 by Western blot; furthermore, all of them could bind IgE by ELISA, in which QME5 seemed to be the best. Flow cytometry analysis displayed that only QME5 could bind membrane IgE and it could compete with membrane FcɛRIα to bind soluble IgE. Meanwhile, QME5 couldn’t bind FcɛRIα-attached IgE, which suggested no hypersensitivity in triggering the target cells (mast cells or basophils) by crosslinking or inducing the release of a variety of chemical mediators.