IgG4 isotype antibodies can interact with FcγRIIb on the surface of macrophages (see Table 1), and this may lead to impaired antitumor responses.118,119 Consistent with the reported immune-modulating effects of IgG4, elevated serum levels of IgG4 in patients with melanoma have been associated with poorer prognosis.117,120 Further work is needed to investigate how these interactions may contribute to melanoma growth and survival and may reveal new prognostic markers, and strategies to interrupt this pro-tumor signaling pathway. This evidence concerns the gene FCGR2B and melanoma.