CD40LG and chronic idiopathic urticaria: In contrast, Type IIb autoimmunity is primarily mediated by IgG autoantibodies, although IgA or IgM autoantibodies may also be involved, as demonstrated by Altrichter et al., who showed that IgM and IgA in addition to IgG autoantibodies against FcεRIα are frequent and associated with disease markers of chronic spontaneous urticaria (3, 4).