The effect of leptin administration during starvation on thymic histology in C57BL/6 mice. (a and b) Ad libitum–fed controls. (c and d) PBS-treated starved mice. (e and f) Leptin-treated starved mice. Sections are stained with H&E and shown at ×25 (a, c, and e) and ×250 (b, d, and f). c, cortex; m, medulla; a, apoptotic thymocytes.