Pre-S_2抗原是由Pre-S_2基因编码55个氨基酸组成的蛋白质,在HBV侵入肝细胞的过程中起链桥作用。Pre-S_2能引起体液、细胞免疫反应,抗PreS_2是中和抗体,对机体起保护作用。测定妊娠妇女血清Pre-S_2滴度能预测母-婴传播的感染率。本项研究中测定肝炎病人血清90份,结果显示:69名乙肝病人,43例(62.3%)Pre-S_2阳性,而非乙肝病人21例中无1例阳性。进一步分析显示Pre-S_2阳性在HBV-DNA、HBsAg HBeAg和抗-HBc阳性组中分别为:76%(16/21), The Pre-S 2 antigen is a 55 amino acid protein encoded by the Pre-S 2 gene, which plays a role of bridge in the intrusion of HBV into hepatocytes. Pre-S_2 can cause humoral and cellular immune response, anti-PreS_2 is neutralizing antibody, the body plays a protective role. Determining the Pre-S 2 titer in pregnant women can predict the infection rate of mother-infant transmission. In our study, 90 serum samples from hepatitis patients were tested. The results showed that 69 hepatitis B patients were positive for Pre-S 2 in 43 patients (62.3%), and none of the 21 hepatitis B patients. Further analysis showed that Pre-S 2 positive in HBV-DNA, HBsAg HBeAg and anti-HBc positive group were: 76% (16/21),