The formation of antigen-antibody complexes plays a fundamental role in our immune defense system. Interaction of these complexes with many cells of the immune system results in a variety of critical functions, including phagocytosis, antibody-dependent cytotoxicity, modulation of antibody secretion, cell secretion and sometimes the secretion and generation of an array of mediators that induce allergic inflammations (Ref.1). Receptors involved in antigen recognition by cells of the immune system include BCRs (B-Cell Receptors), TCRs (T-Cell Receptors), and the FcRs (Fc Receptors) that bind to their corresponding Igs (Immunoglobulins) through Fc domains. FcRs exist for every antibody class: Fc-GammaRs bind IgG, Fc-AlphaRs bind IgA, FcEpsilonRs bind IgE, FcMuRs bind IgM and FcDeltaRs bind IgD (Ref.2). The multisubunit high-affinity IgE receptor, FcEpsilonRI (FcEpsilonReceptorI) expressed [...]