ZHANG Wei, Department ofNeurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China (Tel: 86-10- 13810202944. Email: zhangweivincent@yahoo.com.cn) ZHANG Quan-geng, Department ot Immunology, Capital Medical University, Beijing 100069, China (Tel: 86-10-1860 1061465. Email: zhangqg@ccmu.edu.cn)