CD300E and obesity due to melanocortin 4 receptor deficiency: This study aimed at i) investigating if CD300e elicits an antibody response in patients with obesity and if the antibody titer declines after surgery-induced weight loss, ii) verifying if the anti-CD300e titer before weight loss might be predictive for the improvement of insulin sensitivity and glucose metabolism, and iii) exploring CD300e-specific T cell-responses both in the peripheral blood and in adipose tissues.