LEP and obesity due to melanocortin 4 receptor deficiency: Leptin, whose circulating levels are higher in patients with obesity, acts on immune cells, leading to the stimulation of the production of proinflammatory cytokines and reactive oxygen species, chemotaxis, phagocytosis, and proliferation, as well as the polarization of the Th1/Th17 axis in lymphocytes [184,185].