IL1RL2 and obesity due to melanocortin 4 receptor deficiency: In an effort to explore mechanistically how the IL-36 family might regulate obesity and metabolic disease, we investigated what role, if any, these cytokines might play in disease pathogenesis in mice with a deficiency in the IL-36 receptor antagonist (Il36rn−/−) and the IL-36 receptor (Il1rl2−/−).