HbsAg

Hepatitis B surface antigen (HBsAg) is the coat protein of hepatitis B virus (HBV), which is a glycosylated protein produced by the S gene expression of mature HBV. HbsAg itself is not toxic, but it can bind to liver cell surface receptors to mediate virus invasion, and then its accumulation will induce endoplasmic reticulum stress, ultimately leading to cell damage and even carcinogenesis. Therefore, HbsAg can be used in the research and diagnosis of chronic hepatitis, cirrhosis, and hepatocellular carcinoma caused by HBV infection. Moreover, HbsAg can increase inflammation by initiating the P38 MAPK pathway, accelerate cell cycle by activating Cyclin A and CDK2, and stimulate tumor development by up-regulating GRP78 and GRP94. However, the positivity rate of HbsAg in liver cancer is lower than that in para-carcinoma tissue, speculated that it is caused by HBV gene mutation or coding inhibition. In addition, the high deposition of HbsAg is found in pediatric membranous nephropathy, suggesting that it may be one of the pathogenic antigens of HBV related nephropathy.