In the rAreg/PNE or rOSM/PNE sensitized FT+/− pups which had increased anti-PNE specific IgG1, the IgG1 may have limited the oral PN-induced anaphylaxis because IgG1 binds to FcγRIIb which functions to limit the acute effector functions of mast cells and basophils (68). The gene discussed is FCGR2B; the disease is anaphylaxis.