目的：研究出生前、后小鼠胸腺Ｓ１００蛋白的表达。方法：用免疫组织化学方法对小鼠胸腺Ｓ１００蛋白的表达时间、表达强弱及分布进行原位观察。结果：孕第１７、１９天胎鼠胸腺未见任何Ｓ１００蛋白表达；新生鼠及生后１～５周小鼠胸腺仅呈现极弱的Ｓ１００蛋白表达；生后６周小鼠胸腺Ｓ１００蛋白表达明显增强，并达到最高峰；６周后Ｓ１００蛋白表达又明显减弱。结论：小鼠胸腺Ｓ１００蛋白表达的强弱与小鼠年龄的增长具有相关性 Objective: To study the expression of S100 protein in thymus of mice before and after birth. Methods: Immunohistochemical method was used to detect the expression time, the expression and distribution of S100 protein in mouse thymus in situ. Results: On the 17th and 19th day of pregnancy, no expression of S100 protein was found in the thymus of the fetus; in the newborn and 1 ~ 5 weeks after birth, the mouse thymus showed only weak expression of S100 protein; at 6 weeks after birth, S100 protein expression increased significantly, and reached its peak; S100 protein expression was significantly weakened after 6 weeks. Conclusion: The expression of S100 in thymus of mice is related to the growth of mice