In situ ultrastructural detection and quantitation of liver mononuclear phagocytes in contact with hepatocytes in chronic type B hepatitis.

An ultrastructural cytochemical method for detection of endogenous peroxidase was used to quantify the mononuclear phagocytes present in areas of tissue injury, i.e., in membrane contacts with hepatocytes, in liver biopsies from 12 patients with chronic type B hepatitis; 10 of them exhibited stable disease activity of various degrees of severity, and the other two displayed acutely exacerbated disease activity. Results were compared with those for three patients with acute type B hepatitis. The total percentage of mononuclear phagocytes was higher in patients with chronic hepatitis with stable high disease activity than in patients with stable low disease activity (31.3 +/- 7.4 versus 15.6 +/- 4.7%, p less than 0.01). Furthermore, in the former group of patients, recently recruited macrophages were significantly more frequent than in patients with low disease activity (11.6 +/- 4.0 versus 3.5 +/- 3.6%, p less than 0.01), and macrophages often displayed a markedly hypertrophied cytoplasm with numerous phagolysosomes, suggestive of an activated state. On the other hand, no significant differences in the percentage of the other leukocytes in contact with hepatocytes (lymphocytes, plasmocytes, and polymorphonuclear leukocytes) were noted between patients with high and low disease activity. In the three biopsies obtained from two patients with chronic hepatitis with acute exacerbation of disease activity, the profile of the leukocytes in contact with hepatocytes strikingly resembled the one observed in the three patients with acute type B hepatitis. In both instances, mononuclear phagocytes were rare, and a higher proportion of lymphocytes was observed than in patients with stable chronic liver disease activity. These results suggest that the mechanisms of hepatocyte necrosis in chronic type B hepatitis may differ from that in acute hepatitis due to this virus. Although lymphocyte-mediated mechanisms are likely to be predominant during acute episodes of hepatocyte necrosis, mechanisms mediated by mononuclear phagocytes might play a significant role in the low grade of hepatocyte necrosis characteristic of stable chronic type B hepatitis.