IMMUNOHISTOCHEMICAL STUDY OF GAMMA-DELTA-T-CELL RECEPTOR-POSITIVE CELLS IN THE CAPSULAR REGION OF HEPATOCELLULAR-CARCINOMA - POSSIBLE ROLE IN DEFENSE AGAINST EXPANSION OF CARCINOMA IN THE LIVER

The localization and distribution of gamma delta T cell receptor (TCR) -positive cells (gamma delta T cells) in hepatocellular carcinoma caps ules was investigated immunohistochemically at both light and electron microscopic levels. Most of the mononuclear cells infiltrating the tu mor capsules were CD3-positive. Together with gamma delta T cells, the y were significantly increased in the tumor capsules compared to amoun ts in the fibrous septa in non-cancerous cirrhotic areas of the same l iver, and cirrhosis. Phenotypic characterization by the two-color doub le-staining technique showed that CD8/gamma delta cells were significa ntly increased in the tumor capsule, and that more than one-third of g amma delta TCR-positive cells also expressed the CD56 antigen. Morphol ogical observation revealed that large gamma delta T cells were increa sed in number in the tumor capsule and that the cytoplasm of these cel ls contained multivesicular bodies and dense granules. These morpholog ical features were similar to those of large granular lymphocytes, and most of the gamma delta T cells were also positive for BB3. This sugg ests that extrathymic maturation of gamma delta T cells occurs in the tumor capsule, and that these gamma delta T cells may have a cytolytic effect on tumor cells, as shown in large granular lymphocytes; furthe r, the results suggest that these cells may play a role in the defense against tumor expansion.