Cellular immunity before and after leptin replacement therapy

Background: The few identified leptin-deficient children have immune deficiency. Aims: To evaluate whether a newly-identified leptin-deficient boy has immune defects; to assess the immune changes during leptin replacement. Methods: A 5 year-old boy with congenital leptin deficiency was evaluated before, 2 weeks and 6 weeks after the initiation of recombinant methionyl human leptin. Thymic volume was measured by computed tomography. Humoral immunity was assessed by measuring levels of several immunoglobulins. Cellular immunity was evaluated by the analysis of lymphocyte proliferation in response to mitogens. Lymphocyte subsets were quantified by flow cytometry. Results: At baseline, thymic volume was increased. The lymphocyte subsets count and humoral/cellular immunities were normal. After treatment, proliferative response to mitogens increased by 1.5- to 3-fold, and lymphocyte count decreased by 17%. Conclusions: Immune defects are not an obligatory feature of congenital leptin deficiency. Even in the absence of significant immune defects, leptin replacement therapy enhanced T-cell responsiveness.