The effect of chronic leptin administration on (a) body weight, (b) liver weight, (c) splenocyte subpopulations, and (d) thymocyte subpopulations in ob/ob mice. Values represent mean ± SEM. *P < 0.05 vs. ad libitum–fed controls. **P < 0.05, ***P < 0.0005, PBS-treated starved mice vs. both ad libitum–fed and pair-fed control mice.