Although there are studies showing the anti-inflammatory effect of leptin, there are leptin receptors in lung, alveolar epithelium, and macrophages, and leptin plays very important roles in immunity and host defense response, especially for activation of cell mediated immunity, as leptin is regarded as a proinflammatory adipokine in obesity and lung injury, supported by the majority of the clinical trials and animal studies [59]. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.