FIGURE 1. Model illustrating the impact of IgG antibodies on Type I hypersensitivity . Allergens are taken up by antigen presenting cell which present processed antigen to TH cells. TH cells help B cells to produce IgE which binds to FcεRI on the surface of mast cell and sensitize them. Subsequent production of allergen-specific IgG antibodies which neutralizes allergens and/or engage the inhibitory receptor FcγRIIb.