PB-27 PIECEMEAL NECROSIS IS THE EXPRESSION OF HLA-A,8,C RESTRICTED T CELL CYTOTOXlCITY.

G.~_. Ballardini, M__~. Fallani, 6_= Faccani, S.~_. 8erti, F.B. Bianchi, E. Pisi. Istituto di Clinica Medica II, Universita' di Bologna

Piecemeal necrosis is the morphological representation of immune mediated cytotoxicity, which is regarded as the main pathogenic mechanism operating in chronic liver disease. T cytotoxic cell activity is HLA-A,B,C restricted, at least for virally infected cells, but no data are at present available on this mechanism in vivo. Aim of this study was to investigate the relationship between hepatocyte HLA-A,8,C (antibody W6 32, Sere Lab) expression and the distribution of T cells of suppressor-cytotoxic (TSC,Leu 2a) and helper-inducer (THI,Leu 3a, Bscton & Dickinson) phenotypes on cryostat sections from liver biopsies of patients with chronic liver disease of various etiologies. Ninety-two patients were studied for hepatocellular HLA-A,B,C expression by IFL with an avidin-biotin technique. Four main patterns were detected: normal (negative or faint cytoplasmic staining), membrane-like, cytoplasmic and mixed positivity. In piecemeal necrosis areas a cytoplasmic positivity, with or without membrane stainig, was generally observed. Using a double avidin-biotin IFL technique, with monoclonal antibodies to lymphocyte subsets and HLA-A,8,C molecules (as first and second layer, respectively) 22 selected biopsies were studied. THI lymphocytes were detected mainly in central areas of portal tracts, independently from HLA-A,8,C expression, while TSC were found mainly at the periphery of portal tracts, in piecemeal necrosis areas (strongly HLA-A,B,C positive). In some biopsies positive and negative HLA-A,B,C periseptal areas were contemporay detected: TSC cell infiltration (piecemeal necrosis) was not observed in HLA-A,B,C negative areas. These observations confirm that piecemeal necrosis is related to T cell cytotoxicity, demonstrate that HLA-A,B,C expression on hepatocytes may play a role in the genesis of chronic liver damage and that genetic restriction operates also in vivo, independently from the etiology of chronic liver disease.

PB-28 THE ALTERED EXPRESSION OF MAJOR HISTOCOMPATIBILITY ()RC) ANTIGENS IN RAT LIVER AS A DIRECT RESULT OF CHOLESTASIS.

O.K. Innes t Y. Nasafuclti t B.J. Fuller & K.E.F. Hobbs Academic Department of Surgery, Royal Free Hospital School of Medicine, London NW3 2QG, UK.

Aberrant expression of MHC Class I, cytotoxic T cell target antigens has been demonstrated in the livers of patients with obstructive jaundice and Class II, cytotoxic T cell activating antigens in primary biliary cirrhosis. We have investigated intrahepatic cholestasis as a possible cause of increased expression, in an animal model uncomplicated by biliary sepsis.

Intrahepatic cholestasis was induced in anaesthetised rats by ligation and transection of the bile duct and the rats recovered. Control rats were untreated. Sham operated rats recieved laparotomy only. Rats were killed 1,7 and 21 days post bile duct ligation (BDL). ~C antigens were detected by indirect fluorescence immunohistochemistry. Bile samples were cultured for bacteria. Total serum hilirubin was measured in blood samples to confirm jaundice. There was no evidence of viral infection. The results are summarised below.

Serum Group Number Bilirubin

n m~JlO0.~_ + / - SEM Control 5 0.15+/-0.07 - Sham operated 4 0.29+/-0.I0 BDL (i day) 5 5.87+/-0.27 +7- BDL (7 days) 5 10.18+/-2.51 ++ BDL (21 days) 5 11.35+/-1.4o +H-

~C antigen display on Bile hepatocytes and bile duct cells, sterility

Class I Class II Yes Yes Yes Yes Yes

We conclude that cholestasis alone in the absence of biliary sepsis can increase the expression of Class I antigens on hepatocytes and bile duct cells but not Class II. Therefore we suggest that cholestasis may play a part in the increased immune activity of any liver disease with an autoimmune component but does not initiate the reaction.

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