Localization of hepatitis B surface antigen in the human parotid gland

Localization of hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg) in the human parotid gland and liver was studied by an immunohistochemical method in four cases with seropositive HBsAg. Neither HBsAg nor HBcAg could be detected in the parenchymal cells of the parotid gland in any of the cases. However, one of four cases, which had the highest titer of serum HBsAg, showed HBsAg immunoreactivity in the vascular wall and luminal fluid of the parotid gland. In liver, HBsAg was detected in three and HBcAg in two of the four cases, respectively. HBsAg was localized in the cytoplasm of hepatocytes, while HBcAg was localized mainly in their nuclei. The detection of HBsAg in the parotid gland and liver was correlated with the serum titer of the antigen. The results indicate that the HB virus does not have an affinity for or a replicate in the parotid gland. Also, it is suggested that the HBsAg found in saliva is derived from HBsAg circulating through the oral mucosa by capillary leakage and not from secretion into the mouth by the salivary gland.