Abstract: Immunotherapeutic proteins comprising at least one heavy chain polypeptide derived from an IgG2 antibody are disclosed, wherein the heavy chain polypeptide comprises at least constant heavy domains 2 and 3 (CH2 and CH3) and the lower hinge, and the sequence of the lower hinge comprises a mutation enabling the immunotherapeutic protein to bind to and/or activate Fc?RIIb. The immunotherapeutic protein is suitable for use in methods of treating diseases or conditions wherein, for example, the activation of Fc?RIIb (ie for recruitment of the inhibitory functions of Fc?RIIb) is beneficial, such as allergic diseases.