Widespread presence of cytoplasmic HBcAg in hepatitis B infected liver detected by improved immunochemical methods.

Cytoplasmic and cell membrane associated hepatitis B core antigen (HBcAg) were found to be more widespread within infected liver using indirect immunofluorescence on frozen sections than with the widely used direct immunofluorescence method. Fixation of frozen sections with carbon tetrachloride improved tissue histology without reducing the sensitivity of antigen detection. In tissue blocks fixed with formalin or ethanol-acetic acid, detection of HBcAg was reduced in comparison with frozen sections, and many cells containing low concentrations of (usually cytoplasmic and membranous) HBcAg could not be identified even using indirect immunofluorescence or peroxidase-antiperoxidase reactions. In contrast, intracellular hepatitis B surface antigen (HBsAg) was well detected in fixed sections, but membrane associated HBsAg was not detectable after fixation.