Immunohistochemical characterization of hepatic lymphocytes in acute hepatitis A, B, and C.

The distinctive histologic findings in acute hepatitis A, B, and C suggest that different immunological mechanisms are involved in the pathogenesis of these diseases. This study was undertaken to define the immune response in each type of acute hepatitis by identification of the intrahepatic lymphocyte subsets. Thirty paraffin-embedded liver biopsy specimens from 10 patients with acute hepatitis A, 10 patients with acute hepatitis B, and 10 patients with acute hepatitis C were evaluated. Immunohistochemical staining was performed by the indirect immunoperoxidase technique using the following monoclonal or polyclonal antibodies: CD45RO, CD20-cy, CD57, and Mac387. Inflammatory infiltrates varied from specimen to specimen. However, CD45RO+ memory T cells were the predominant infiltrating mononuclear cells in all specimens. In the portal areas, CD45RO+ memory T cells were the most prominent in AHC, followed by AHA and AHB, and the difference between AHC and AHB was statistically significant. CD20-cy+ B cells were seen mainly in the portal areas, and were significantly less common in AHB than in AHA and AHC. In addition, the ratio of CD20-cy+ B cells to CD45RO+ memory was significantly lower in AHB than in the other types of acute hepatitis. The necrotic areas in all specimens contained mainly CD45RO+ memory cells in association with a few CD57+ NK and T cells or CD20-cy+ B cells. Our study revealed differences of the intrahepatic lymphocyte subsets among the various types of acute hepatitis, but the meaning of these differences is presently unknown. Therefore, further studies are required to fully elucidate the mechanism of the immune response in acute hepatitis.