The proportions of CD3+ (P = 0.0324) and CD3+CD4+ (P = 0.0305) T cells in the spleens of mice from undernutrition 65% + infection group were significantly higher than those in normal + infection group or obesity + infection group at the 5th week after infection, but the proportions of CD3+CD4+ (P = 0.0483) and CD3+CD8+ (P = 0.0307) T cells were significantly lower at the 8th week after infection (Fig. 3A, B). The gene discussed is CD8A; the disease is obesity due to melanocortin 4 receptor deficiency.