The role of IgG in allergy has been controversial due to their binding affinity to different Fcγ receptors (FcγRs) which may lead to different immune response outcomes, depending on whether the FcγRs are activating (FcγRI and FcγRIIIa) [53] or inhibitory (FcγRIIb) receptors [54,55] on the immune cells [53,56,57]. The gene discussed is FCGR2B; the disease is allergic disease.