IFNG and obesity due to melanocortin 4 receptor deficiency: Physical alteration of the intestinal barrier in obesity, as evidenced by an enlarged jejunal mucosa surface in obese compared to lean subjects, may also shift gut immunity as indicated by increased IFN-γ-, IL-17-, and IL-22-producing Th1 and Th17 cells in the lamina propria, and increased CD8+ T cell frequency in epithelium.