Two distinct antibody-mediated mechanisms of mast cell activation have been identified: Type I autoallergy (TIaiCSU), in which IgE antibodies are directed against self-antigens and Type IIb autoimmunity (TIIbaiCSU), characterized by the presence of IgG autoantibodies targeting either the α-chain of FcεRI or FcεRI-bound IgE. Here, IGHE is linked to Autoimmunity.