Multiple organ infection and the pathogenesis of SARS

Gu, Jiang; Gong, Encong; Zhang, Bo; Zheng, Jie; Gao, Zifen; Zhong, Yanfeng; Zou, Wanzhong; Zhan, Jun; Wang, Shenglan; Xie, Zhigang; Zhuang, Hui; Wu, Bingquan; Zhong, Haohao; Shao, Hongquan; Fang, Weigang; Gao, Dongshia; Pei, Fei; Li, Xingwang; He, Zhongpin; Xu, Danzhen; Shi, Xeying; Anderson, Virginia M.; Leong, Anthony S.-Y.

Based on our findings, we propose the following pathogenesis mechanism of SARS. The SARS virus enters the body through the respiratory tract and first infects the epithelial cells of the trachea, bronchi, bronchioles, and lungs. The virus infects resident, infiltrating, and circulating immune cells. The circulating immune cells carry the virus to other organs. The virus infects and damages the immune cells of the spleen, peripheral and central lymph nodes, and other lymphoid tissues. The immune defense is weakened significantly, which leads to rapid deterioration of the pneumonia. In the same manner, the blood-borne SARS virus infects other organs. As such, patients who have compromised immune function, such as those who have chronic diseases and aged individuals, suffer a more severe illness and have a much higher mortality from SARS (15) . The extent of immune cell damage, reflected by lymphocyte count, is a manifestation of the patient's immune status and a predictor of outcome. The damage to the immune system, more than damage to the lungs, determines whether a patient recovers or dies from the infection. In a way, the name "sudden acute respiratory syndrome" is inappropriate because it diverts attention from the primary pathologic changes that result from SARS virus infection. It must be emphasized that immune damage most likely is the primary determinant of clinical outcome.