Furthermore, it was shown that patients with obesity and type 2 diabetes produce significantly less IFN-γ in peripheral blood mononuclear cells in response to IL-18 stimulation compared to lean controls, most likely due to reduced expression of the IL-18 receptor β chain, and the authors have introduced a consept of IL-18 resistance as a potential explanation of elevated IL-18 levels in such patients [85]. The gene discussed is IL18; the disease is obesity due to melanocortin 4 receptor deficiency.