LEP and obesity due to melanocortin 4 receptor deficiency: Leptin resistance or desensitization of signaling in obesity (BMI ≥ 30 kg/m2) and over-nutrition impaired antigen-specific IgG response as well as reduced CD69, IFN-γ, and Granzyme-B in CD8+ T cells to influenza vaccination (Sheridan et al., 2012).