Immunohistochemical analysis of HLA (A, B, C) antigens in liver disease using a monoclonal antibody

New insights on the role of human leukocyte antigen complex in primary biliary cholangitis

Primary Biliary Cholangitis (PBC) is a rare autoimmune cholangiopathy. Genetic studies have shown that the strongest statistical association with PBC has been mapped in the human leukocyte antigen (HLA) locus, a highly polymorphic area that mostly contribute to the genetic variance of the disease. Furthermore, PBC presents high variability throughout different population groups, which may explain the different geoepidemiology of the disease. A major role in defining HLA genetic contribution has been given by genome-wide association studies (GWAS) studies; more recently, new technologies have been developed to allow a deeper understanding. The study of the altered peptides transcribed by genetic alterations also allowed the development of novel therapeutic strategies in the context of immunotolerance. This review summarizes what is known about the immunogenetics of PBC with a focus on the HLA locus, the different distribution of HLA alleles worldwide, and how HLA modifications are associated with the pathogenesis of PBC. Novel therapeutic strategies are also outlined.

Immune system and cholangiocytes: A puzzling affair in primary biliary cholangitis

Primary biliary cholangitis (PBC) is a cholestatic liver disease characterized by the destruction of the small and medium bile ducts. Its pathogenesis is still unknown. Despite the genome wide association study findings, the therapies targeting the cytokines pathway, tested so far, have failed. The concept of the biliary epithelium as a key player of the PBC pathogenesis has emerged over the last few years. It is now well accepted that the biliary epithelial cells (BECs) actively participate to the genesis of the damage. The chronic stimulation of BECs via microbes and bile changes the cell phenotype toward an active state, which, across the production of proinflammatory mediators, can recruit, retain, and activate immune cells. The consequent immune system activation can in turn damage BECs. Thus, the crosstalk between both innate and adaptive immune cells and the biliary epithelium creates a paracrine loop responsible for the disease progression. In this review, we summarize the evidence provided in literature about the role of BECs and the immune system in the pathogenesis of PBC. We also dissect the relationship between the immune system and the BECs, focusing on the unanswered questions and the future potential directions of the translational research and the cellular therapy in this area.

Natural killer T cells mediate inflammation in the bile ducts

Cholangiocytes function as antigen-presenting cells with CD1d-dependent activation of natural killer T (NKT) cells in vitro. NKT cells may act both pro- and anti-inflammatory in liver immunopathology. We explored this immune pathway and the antigen-presenting potential of NKT cells in the bile ducts by challenging wild-type and Cd1d-/- mice with intrabiliary injection of the NKT cell activating agent oxazolone. Pharmacological blocking of CD1d-mediated activation was performed with a monoclonal antibody. Intrabiliary oxazolone injection in wild-type mice caused acute cholangitis with significant weight loss, elevated serum levels of alanine transaminase, aspartate transaminase, alkaline phosphatase and bilirubin, increased histologic grade of cholangitis and number of T cells, macrophages, neutrophils and myofibroblasts per portal tract after 7 days. NKT cells were activated after intrabiliary injection of oxazolone with upregulation of activation markers. Cd1d-/- and wild-type mice pretreated with antibody blocking of CD1d were protected from disease. These findings implicate that cells in the bile ducts function as antigen-presenting cells in vivo and activate NKT cells in a CD1d-restricted manner. The elucidation of this biliary immune pathway opens up for potentially new therapeutic approaches for cholangiopathies.

HLA and Histo-Blood Group Antigen Expression in Human Pluripotent Stem Cells and their Derivatives

One prerequisite for a successful clinical outcome of human pluripotent stem cell (hPSC) based therapies is immune compatibility between grafted cells/tissue and recipient. This study explores immune determinants of human embryonic stem cell lines (hESC) and induced human pluripotent stem cell (hiPSC) lines and hepatocyte- and cardiomyocyte-like cells derived from these cells. HLA class I was expressed on all pluripotent hPSC lines which upon differentiation into hepatocyte-like cells was considerably reduced in contrast to cardiomyocyte-like cells which retained class I antigens. No HLA class II antigens were found in the pluripotent or differentiated cells. Histo-blood group carbohydrate antigens SSEA-3/SSEA-4/SSEA-5, Globo H, A, Le^x/Le^y and sialyl-lactotetra were expressed on all hPSC lines. Blood group AB(O)H antigen expression was in accordance with ABO genotype. Interestingly, only a subpopulation of A1O1 cells expressed A. During differentiation of hPSC, some histo-blood group antigens showed congruent alteration patterns while expression of other antigens differed between the cell lines. No systematic difference in the hPSC cell surface tissue antigen expression was detected. In conclusion, hPSC and their derivatives express cell surface antigens that may cause an immune rejection. Furthermore, tissue antigen expression must be established for each individual stem cell line prior to clinical application.

Drug-induced bile duct injury

Drug-induced liver injury includes a spectrum of pathologies, some related to the mode of injury, some to the cell type primarily damaged. Among these, drug-induced bile duct injury is characterized by the destruction of the biliary epithelium following exposure to a drug. Most of the drugs associated with bile duct injury cause immune-mediated lesions to the epithelium of interlobular ducts. These share common histopathological features with primary biliary cholangitis, such as inflammation and necrosis at the expense of cholangiocytes and, if the insult persists, bile duct loss and biliary cirrhosis. Some drugs selectively target larger ducts. Such injury is often dose-dependent and thought to be the result of intrinsic drug toxicity. The histological changes resemble those seen in primary sclerosing cholangitis. This overview focuses on the clinical and pathological features of bile duct injury associated with drug treatment and on the immunological and biochemical effects that drugs exert on the biliary epithelium. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

The biliary epithelium presents antigens to and activates natural killer T cells

Cholangiocytes express antigen-presenting molecules, but it has been unclear whether they can present antigens. Natural killer T (NKT) cells respond to lipid antigens presented by the major histocompatibility complex class I-like molecule CD1d and are abundant in the liver. We investigated whether cholangiocytes express CD1d and present lipid antigens to NKT cells and how CD1d expression varies in healthy and diseased bile ducts. Murine and human cholangiocyte cell lines as well as human primary cholangiocytes expressed CD1d as determined by flow cytometry and western blotting. Murine cholangiocyte cell lines were able to present both exogenous and endogenous lipid antigens to invariant and noninvariant NKT cell hybridomas and primary NKT cells in a CD1d-dependent manner. A human cholangiocyte cell line, cholangiocarcinoma cell lines, and human primary cholangiocytes also presented exogenous CD1d-restricted antigens to invariant NKT cell clones. CD1d expression was down-regulated in the biliary epithelium of patients with late primary sclerosing cholangitis, primary biliary cirrhosis, and alcoholic cirrhosis compared to healthy controls.

CONCLUSIONS

Cholangiocytes express CD1d and present antigens to NKT cells and CD1d expression is down-regulated in diseased biliary epithelium, findings which show that the biliary epithelium can activate an important lymphocyte subset of the liver. This is a potentially important immune pathway in the biliary system, which may be capable of regulating inflammation in the context of biliary disease.

Intractable ascites without mechanical vascular obstruction after orthotopic liver transplantation: etiology and clinical outcome of sinusoidal obstruction syndrome

Intractable ascites after orthotopic liver transplantation (OLT) is a relatively rare complication. However, it often takes a life threatening course, which requires re-transplantation. In previous studies, several reports gave hepatic sinusoidal obstruction syndrome (SOS) as one of the causes of refractory ascites. However, the detailed etiology of SOS after OLT and its association with clinical consequences remain unclear because there have been few studies to date. We report two recent cases with rapidly progressive refractory ascites associated with SOS, following completely different clinical courses. In case 1, the first episode of acute allograft rejection triggered SOS and subsequent intractable ascites, while the second acute rejection worsened his clinical status. A transjugular intrahepatic portosystemic stent-shunt (TIPS) was placed and this procedure resulted in complete disappearance of ascites and of renal dysfunction. In contrast, refractory ascites in case 2, who had neither rejection nor mechanical outlet obstruction, worsened despite TIPS stent placement, and re-transplantation was necessary. We speculate that the pre-existing diseased liver of the cadaver donor caused this serious complication, necessitating a second graft.

Significance of C4d staining in ABO-identical/compatible liver transplantation

Complement degradation product C4d has become an important marker of humoral or antibody-mediated rejection in renal and heart allograft biopsies. Although there have been several reports on the detection of C4d in liver allografts, the significance of C4d in liver transplantation and its relationship with humoral rejection are still not clear. We investigated the frequency and pattern of C4d staining in liver allograft biopsies with reference to preoperative lymphocyte crossmatch tests, which detect donor-reactive lymphocyte antibody. Survival rates at 5 years were 77% for crossmatch-negative patients and 53% for crossmatch-positive patients (P=0.009). In crossmatch-negative patients, reproducible positive staining was obtained in 28 of 86 (33%) biopsies taken within 90 days after transplantation and 33 of 96 (34%) biopsies 90 days or after transplantation. Most C4d staining was observed in the portal areas, and no clear correlation was observed between C4d positivity and histological diagnosis. In crossmatch-positive patients, 9 of 11 (82%) biopsies showed positivity for C4d. C4d stained perivenular areas as well as portal areas. Histology of crossmatch-positive patients included acute rejection and cholangitis, but did not include periportal changes that were seen in humoral rejection in ABO-incompatible liver transplantation. In summary, focal C4d deposition was seen in various types of liver allograft injury and had little clinical impact on crossmatch-negative patients, but extensive C4d staining in crossmatch-positive patients may be associated with humoral rejection and poor graft survival.

The level of viral antigen presented by hepatocytes influences CD8 T-cell function

CD8 T cells exert their antiviral function through cytokines and lysis of infected cells. Because hepatocytes are susceptible to noncytolytic mechanisms of viral clearance, CD8 T-cell antiviral efficiency against hepatotropic viruses has been linked to their capacity to produce gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). On the other hand, intrahepatic cytokine production triggers the recruitment of mononuclear cells, which sustain acute and chronic liver damage. Using virus-specific CD8 T cells and human hepatocytes, we analyzed the modulation of virus-specific CD8 T-cell function after recognition peptide-pulsed or virally infected hepatocytes. We observed that hepatocyte antigen presentation was generally inefficient, and the quantity of viral antigen strongly influenced CD8 T-cell antiviral function. High levels of hepatitis B virus production induced robust IFN-gamma and TNF-alpha production in virus-specific CD8 T cells, while limiting amounts of viral antigen, both in hepatocyte-like cells and naturally infected human hepatocytes, preferentially stimulated CD8 T-cell degranulation. Our data document a mechanism where virus-specific CD8 T-cell function is influenced by the quantity of virus produced within hepatocytes.

T lymphocytes interact with hepatocytes through fenestrations in murine liver sinusoidal endothelial cells

The liver has an established ability to induce tolerance. Recent evidence indicates that this unique property might be related to its distinctive architecture allowing T cells to be activated in situ independently of lymphoid tissues. Unlike lymph node-activated T cells, liver-activated T cells are short-lived, a mechanism that might contribute to the "liver tolerance effect." Although the potential role of hepatocytes as tolerogenic antigen-presenting cells has been demonstrated, the question as to whether these cells are able to interact with CD8(+) T cells in physiological settings remains controversial. Contradicting the immunological dogma stating that naïve T lymphocytes are prevented from interacting with parenchymal cells within non-lymphoid organs by an impenetrable endothelial barrier, we show here that the unique morphology of the liver sinusoidal endothelial cell (LSEC) permits interactions between lymphocytes and hepatocytes. Using electron microscopy, we demonstrate that liver resident lymphocytes as well as circulating naïve CD8(+) T cells make direct contact with hepatocytes through cytoplasmic extensions penetrating the endothelial fenestrations that perforate the LSECs. Furthermore, the expression of molecules required for primary T cell activation, MHC class I and ICAM-1, is polarized on hepatocytes to the perisinusoidal cell membrane, thus maximizing the opportunity for interactions with circulating lymphocytes. In conclusion, this study has identified, at the ultrastructural level, a unique type of interaction between naïve T lymphocytes and liver parenchymal cells in vivo. These results hold implications for the pathogenesis of viral hepatitis in which hepatocytes may represent the main antigen-presenting cell, and for the development of immune tolerance as lymphocytes pass through the liver.

Hepatocytes express abundant surface class I MHC and efficiently use transporter associated with antigen processing, tapasin, and low molecular weight polypeptide proteasome subunit components of antigen processing and presentation pathway

Hepatic expression levels of class I MHC Ags are generally regarded as very low. Because the status of these Ags and their ability to present peptides are important for the understanding of pathogen clearance and tolerogenic properties of the liver, we set out to identify the factors contributing to the reported phenotype. Unexpectedly, we found that the surface densities of K(b) and D(b) on C57BL/6 mouse hepatocytes are nearly as high as on splenocytes, as are the lysate concentrations of mRNA encoding H chain and beta(2)-microglobulin (beta(2)m). In contrast, the components of the peptide-loading pathway are reduced in hepatocytes. Despite the difference in the stoichiometric ratios of H chain/beta(2)m/peptide-loading machineries, both cell types express predominantly thermostable class I and are critically dependent on TAP and tapasin for display of surface Ags. Minor differences in the expression patterns in tapasin(-/-) background suggest cell specificity in class I assembly. Under immunostimulatory conditions, such as exposure to IFN-gamma or Listeria monocytogenes, hepatocytes respond with a vigorous mRNA synthesis of the components of the Ag presentation pathway (up to 10-fold enhancement) but up-regulate H chain and beta(2)m to a lesser degree (<2-fold). This type of response should promote rapid influx of newly generated peptides into the endoplasmic reticulum and preferential presentation of foreign/induced Ag by hepatic class I.

Intratumoral T-cell infiltrates and MHC class I expression in patients with stage IV melanoma

The infiltration of tumors by T cells has been shown to correlate with prolonged patients' survival. However, it remains unclear why only some tumors are infiltrated with T cells. This study was designed to investigate possible correlations between intratumoral T-cell infiltrates and the expression of cancer-associated antigens and MHC class I and II molecules in patients with melanoma. Fresh frozen samples from 124 stage IV melanoma patients were analyzed by immunohistochemistry for the expression of Melan-A/MART-1, tyrosinase, gp100, NY-ESO-1, and MHC class I and II. Intratumoral T-cell and B-cell infiltrates were detected by staining with anti-CD4, anti-CD8, anti-CD3, and L26 antibodies. The NY-ESO-1 serum antibody status was assessed by Western blot analysis. Intratumoral CD8+ and CD4+ T cells were detected in 63.9% and 71.3% of patients, respectively. We observed a significant heterogeneity of the expression of the melanocyte differentiation antigens, NY-ESO-1, and MHC class I and II molecules. The only significant correlation was found between the expression of MHC class I and the presence of CD4+ and CD8+ T cells (P < 0.0001). There was a strong association between these two variables with respect to the density and distribution of infiltrating T cells and the pattern of MHC class I expression (focal versus homogenous). Intratumoral T-cell infiltration is closely correlated with the MHC class I expression but not with the expression of differentiation antigens, cancer-associated antigens, or MHC class II molecules. These results may have implications for the definition of prognostic variables and for the identification of patients who may benefit from antigen-specific cancer immunotherapy.

Review article: immunopathogenetic and therapeutic aspects of autoimmune hepatitis

Autoimmune hepatitis is a chronic, progressive liver disease that responds well to immunosuppressive therapy, but has a poor prognosis if untreated. Possible triggering factors include viruses, other autoimmune disorders and drugs. The molecular mechanisms contributing to the pathogenesis include: reactions of autoantibodies against their corresponding autoantigens; aberrant expression of histocompatibility antigen class I and II molecules, cell adhesion molecules and cytokines; increased oxidative stress; and the occurrence of angiogenesis. The prevalence of the disease is highest in Caucasians, Europeans and women. The natural history of autoimmune hepatitis shows a poor prognosis, with frequent progression to cirrhosis and hepatic insufficiency in untreated patients. The occurrence of hepatocellular carcinoma is rare and is found only in long-standing cirrhosis. Corticosteroids as monotherapy or in combination with azathioprine are the treatments of choice; different therapeutic schedules and particularities of treatment for pregnant women and children have been established. To avoid treatment-associated adverse effects, alternative therapies have been proposed, including ciclosporin, budesonide, tacrolimus, mycophenolate mofetil, ursodeoxycholic acid, methotrexate, cyclophosphamide, mercaptopurine and free radical scavengers. Liver transplantation is indicated for patients refractory to or intolerant of immunosuppressive therapy.

Serum concentrations of soluble HLA-class I and CD8 forms in patients with viral hepatic disorders

Soluble HLA-class I and CD8 molecules were determined by sandwich ELISA in patients with viral-induced hepatic disorders. As a whole, the patients with hepatic disorders (acute hepatitis: AH; chronic hepatitis: CH; liver cirrhosis: LC; hepatocellular carcinoma: HCC) showed higher sHLA-class I and sCD8 levels than normal controls (P < 0.001). AH patients had the highest sHLA-class I levels (mean, 3513 +/- 2112 ng/ml), followed by CH (2896 +/- 1290 ng/ml), LC (2293 +/- 1266 ng/ml), and HCC (2221 +/- 1212 ng/ml) sCD8 levels wer highest in AH, followed by HCC, LC, and CH, in that order. Among histologically defined C virus-positive patients, sHLA-I levels were higher in those with chronic active hepatitis (CAH) 2A (3802 +/- 1124 ng/ml) than in those with chronic persistent hepatitis (CPH; 2200 +/- 711 ng/ml; P < 0.01), the levels then decreased as the disease progressed (CAH2B, 3564 +/- 1783 ng/ml, LC, 2376 +/- 1265 ng/ml). In contrast, sCD8 values showed little difference among the disorders. sHLA-class I levels showed a positive correlation with sCD8 values both in whole patients and in patients with AH (P < 0.01), but no correlation was shown, in any patients, with biochemical parameters such as GPT and GOT. These findings, taken together, suggest that hepatic destruction is not the only cause of sHLA-class I production, but that sHLA-class I levels, together with sCD8 levels, may reflect immunological activity in hepatic disorders.

Immunopathology of hepatitis C

Hepatitis C virus (HCV) infection becomes persistent in the majority of instances in the face of a humoral and cellular immune response, and persistent HCV infection is associated with chronic hepatitis. In particular, cytotoxic T lymphocytes (CTL), crucial in the eradication of virus-infected cells, have been observed in the liver and the peripheral blood of chronically infected patients, suggesting that CTL cannot completely eliminate the virus, and may contribute to chronic liver injury. In this review, the potential host and the viral factors involved in the pathogenesis of chronic HCV infection will be discussed with emphasis on the HLA-A2 restricted peripheral blood CTL response and its relationship to liver disease and viral load.

Identification of woodchuck class I MHC antigens using monoclonal antibodies

Two class I major histocompatibility complex (MHC) proteins with molecular masses of 43- and 39-kDa were identified in the cell surface membranes of normal woodchucks using a newly developed antiwoodchuck class I monoclonal antibody (mAb) B1b.B9 and immunoblotting. B1b.B9 was generated by immunizing mice with viable woodchuck peripheral blood mononuclear cells and was selected for anti-class I MHC reactivity using a cellular enzyme-linked immunoassay, indirect immunofluorescence on tissue sections and flow cytofluorimetry. The distribution pattern of class I MHC antigen on woodchuck lymphoid cells was found to be similar to that reported in other species. Also, the antigen expression on normal woodchuck hepatocytes was comparable to that observed on normal human liver parenchymal cells; thus, the antigen was not detected on hepatocytes by staining of liver tissue sections, but was found by indirect immunofluorescence staining of isolated liver cells. Western blot analysis of the plasma membranes from normal woodchuck hepatocytes revealed the presence of a single species of class I MHC heavy chain protein with a molecular mass of 43-kDa, whereas splenocyte plasma membranes showed intense expression of a 43-kDa species, as well as the presence of a 39-kDa protein. The 39- and 43-kDa proteins were extracted with Triton X-114 to the hydrophobic protein phase, suggesting that they both contain a hydrophobic transmembrane domain. The data obtained indicate that the B1b.B9 identifies a nonpolymorphic epitope of woodchuck class I MHC heavy chains, providing an important reagent for the study of the pathogenesis of hepatitis B virus infection in a woodchuck model.

Effects of bile acids and cholestasis on major histocompatibility complex class I in human and rat hepatocytes

BACKGROUND/AIMS

Major histocompatibility complex (MHC) class I molecules, which are normally poorly expressed on the surface of hepatocytes, are overexpressed during cholestasis. The mechanisms responsible for this overexpression were examined.

METHODS

The expression of class I molecules, assessed by flow cytofluorimetry, and the class I messenger RNA (mRNA) transcripts, assessed by Northern blot analysis, were measured on normal human hepatocytes in primary culture.

RESULTS

Chenodeoxycholic acid induced an overexpression of MHC class I molecules, whereas ursodeoxycholic acid did not. The level of class I mRNA closely reflected that of the membrane protein. Moreover, cholestasis, induced in the rat by ligation-section of the common bile duct, increased the MHC class I mRNA level. Actinomycin D inhibited bile acid-induced class I transcription of rat hepatocytes in primary culture, whereas cycloheximide did not. Finally, class I mRNA expression was induced in hepatocytes by phorbol myristate acetate and by forskolin. This hyperexpression, as well as that observed with chenodeoxycholic acid, was suppressed by an inhibitor of protein kinase C and protein kinase A.

CONCLUSIONS

Taken together, these results suggest that chenodeoxycholic acid, as interferon, activates protein kinase C and protein kinase A, resulting in the induction of MHC class I expression.

Coexpression of intercellular adhesion molecule-1 and class I major histocompatibility complex antigens on hepatocyte membrane in chronic viral hepatitis

AIMS

To evaluate the role of hepatocyte expression of leucocyte adhesion molecules and major histocompatibility complex (MHC) antigens in the pathogenesis of chronic viral hepatitis.

METHODS

The expression of intercellular adhesion molecule 1 (ICAM-1), lymphocyte function associated antigen 3 (LFA-3), and MHC class I and II antigens on hepatocyte membrane in relation to the histological and biochemical activities was studied in patients with chronic B hepatitis, chronic persistent hepatitis (CPH) n = 23; chronic active hepatitis (CAH) n = 20; chronic D hepatitis (CAH) n = 6; and chronic non-A, non-B hepatitis (CPH n = 4, CAM n = 6). Six of the latter were hepatitis C virus antibody positive.

RESULTS

In chronic B hepatitis ICAM-1 and MHC-I were expressed significantly more in patients with CAH than in those with CPH (p < 0.001), while the expression of LFA-3 and MHC-II showed no significant difference, irrespective of serum HBeAg or hepatitis B virus DNA. Similar findings were noted in non-A, non-B hepatitis. Regardless of the viral aetiology, patients with CAH had a significantly higher degree of ICAM-1 and MHC-I expression than LFA-3 (p < 0.001 v ICAM-1 and MHC-I, respectively) and MHC-II (p < 0.001 v ICAM-1 and MHC-I, respectively) expression. Those with CPH showed little or no difference in the expression of these four molecules. Furthermore, serum ALT values positively correlated with the hepatocyte expression of ICAM-1 (p < 0.001) and MHC-I (p < 0.001), but not LFA-3 (p > 0.05) and MHC-II (p > 0.05).

CONCLUSIONS

In chronic viral hepatitis hepatocyte expression of ICAM-1 and MHC-I might be important for immunosurveillance against virally infected hepatocytes, while the expression of LFA-3 and MHC-II does not seem to have a role in the pathogenesis of chronic viral hepatitis.

Intercellular adhesion molecule-1 and MHC antigens on human intrahepatic bile duct cells: effect of pro-inflammatory cytokines

Human intrahepatic biliary epithelial cells were isolated from the livers of patients with primary biliary cirrhosis and from normal livers and established in primary culture. The in vitro expression of intercellular adhesion molecule-1, HLA class I, and HLA class II on biliary epithelial cells was studied in response to tumour necrosis factor-alpha (0-500 U/ml), interferon-gamma (0-500 U/ml), and interleukin-1 (0-5 U/ml) by immunohistochemical staining and a semiquantitative scoring system validated by spectrophotometry and previously validated by laser confocal microscopy. The non-stimulated expression of intercellular adhesion molecule-1 and HLA class II was higher on cells derived from the primary biliary cirrhosis liver than on cells from normal liver, a difference not seen with HLA class I expression. A statistically significant increase in intercellular adhesion molecule-1 expression was seen with all three cytokines in cells derived from both primary biliary cirrhosis and normal liver. Increase in HLA class I expression was seen only with interleukin-1 5 U/ml for cells derived from both normal and diseased liver. Increase in HLA class II expression was seen only with interferon-gamma 500 U/ml for cells derived from diseased liver and with interleukin-1 5 U/ml for cells derived from both diseased and normal liver. These data show that pro-inflammatory cytokines increase expression of intercellular adhesion molecule-1, HLA class I, and HLA class II on human intrahepatic biliary epithelial cells in vitro and are consistent with the hypothesis that these locally acting factors may play a part in the pathogenesis of immune mediated disorders such as primary biliary cirrhosis in which immune mediated bile duct damage occurs.

Immunogenicity of rat hepatocytes in vivo: effect of cholestasis-induced changes in major histocompatibility complex expression

Hepatocytes normally express few major histocompatibility complex (MHC) class I and no MHC class II molecules, a phenomenon which could explain their low immunogenicity. However, in pathological situations, such as allograft rejection and cholestasis, hepatocytes strongly express MHC class I molecules and their immunogenicity could be different. The aim of this study was to assess the role of MHC expression on the immunogenicity of hepatocytes in vivo. Hepatocytes were obtained from normal and cholestatic DA rats by whole-liver perfusion with EDTA. Cholestasis was induced by ligation-section of the common bile duct. MHC expression on hepatocytes was assessed by cytofluorimetry after labelling with monoclonal antibodies against MHC class I and class II antigens. The percentage of hepatocytes expressing MHC class I was 9.8 +/- 2.2% in normal rats and 77.2 +/- 3.3% in cholestatic rats (P = 2 x 10(-4)); MHC class II expression was present on 1 +/- 0.5% of normal hepatocytes and 0.4% +/- 0.1% of cholestatic hepatocytes (P > 0.05). Lewis rats received a DA or Wistar-Furth heart allograft 7 days after intravenous injection of 2 x 10(7) hepatocytes from normal or cholestatic DA rats. The DA heart allograft was rejected in 6.3 +/- 0.4 days in Lewis controls, 8.8 +/- 1.1 days (N.S.) in Lewis recipients that received normal DA hepatocytes and 17.6 +/- 3.0 days (P = 2 x 10(-4)) in Lewis recipients that received hepatocytes from cholestatic DA rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell-mediated hepatic injury in alcoholic liver disease. Veterans Affairs Cooperative Study Group 275

BACKGROUND

The mechanism responsible for the initiation and perpetuation of alcoholic liver disease (ALD) remains poorly understood. This investigation attempted to elucidate the role of cell-mediated immune phenomena in the pathogenesis of ethanol-induced liver injury.

METHODS

Frozen liver biopsy specimens from 144 patients with moderate to severe ALD were examined by the avidin-biotin immunoperoxidase technique for the expression of antigenic markers of T and B lymphocytes, natural killer cells, and class I and II MHC molecules in the tissue.

RESULTS

Expression of CD3 by lymphocytes correlated significantly with regenerating nodules, intralobular inflammation, central sclerosis, and abnormalities of Kupffer cells. B cells were rarely present, and natural killer cells were absent. CD3+ lymphocytes expressed either CD4 or CD8 surface molecules. Enhanced class I MHC expression correlated significantly with portal inflammation, limiting plate erosion, vascular abnormalities, and hemosiderosis. Expression of class II MHC molecules correlated significantly with necrosis, bile stasis, and Mallory bodies.

CONCLUSIONS

The distribution and persistence of CD4+ and CD8+ cells in actively advancing ALD, the enhanced MHC expression on hepatocytes, and their relationship to alcoholic hyalin and necrosis lend support to the hypothesis that a cytotoxic T lymphocyte-hepatocyte interaction plays a role, perhaps via lymphokine production, in the genesis or perpetuation of ALD.

Variability in the expression of a beta 2-microglobulin epitope on hepatocytes in chronic type C hepatitis on treatment with interferon

Cytotoxic CD8+ T lymphocytes recognize viral antigens in the context of human leukocyte antigen class I molecule coexpression by target cells. Analysis of beta 2-microglobulin reactivity is useful in evaluating changes in human leukocyte antigen class I antigen distribution. In this study we analyzed liver biopsy specimens obtained from 15 patients with chronic active hepatitis type C who underwent a clinical trial with recombinant interferon-alpha 2b. We comparatively studied by immunohistochemical analysis the expression of human leukocyte antigen class I antigens in frozen liver samples obtained before entry in the protocol and in specimens taken 8 mo after initiation of treatment. Six normal liver samples were used as controls. For immunohistochemical analysis, a panel of several human leukocyte antigen class I monoclonal antibodies, specific for beta 2-microglobulin or different heavy-chain determinants, was used. In addition, we included a novel monoclonal antibody (HP-1H8), characterized in this report, which is specific for a distinct beta 2-microglobulin epitope. On entry, mean serum ALT was 240 +/- 89 IU/L and mean Knodell's index was 9.9 +/- 2.4, whereas at the time of the second biopsy mean values had diminished to 45 +/- 22 IU/L and 4.7 +/- 3.0, respectively. Liver sections from controls and patients expressed human leukocyte antigen class I light- and heavy-chain determinants in hepatocytes, biliary duct epithelium, sinusoidal lining cells and lymphocytes. Remarkably, the beta 2-microglobulin epitope recognized by the HP-1H8 monoclonal antibody was undetectable on hepatocytes from normal livers but clearly evident on hepatocytes from patients with chronic active hepatitis C before interferon treatment. Positive staining was more intense in areas of piecemeal and lobular necrosis. Double immunostaining with a CD2 monoclonal antibody demonstrated that labeling with HP-1H8 was predominantly associated with T-cell infiltration. Interestingly, the reactivity of HP-1H8 with hepatocytes was diminished or disappeared in specimens obtained during interferon treatment; the pattern of reactivity then resembled that of samples from normal controls. Our data indirectly suggest that, in addition to the increased expression of human leukocyte antigen class I molecules on hepatocytes in viral infections, conformational changes may take place in these antigens. These changes can be revealed by immunostaining with the HP-1H8 monoclonal antibody. Interferon therapy could down-regulate this expression through its effect in reducing the histological activity resulting from the lysis of virus-infected hepatocytes by cytotoxic T cells.

Quantitative immunohistochemical analysis of lymphocyte subsets in alcoholic liver disease

To investigate the role of lymphocytes frequently observed in the parenchyma of alcoholic liver disease (ALD), lymphocytes infiltrating into the liver were stained immunohistochemically with monoclonal antibodies (MoAb) and were quantitatively assessed by a morphometric analysis in 17 patients with ALD and, for comparison in five patients with chronic active hepatitis B (B-CAH). In patients with alcoholic hepatitis, the number of CD8+ lymphocytes in the hepatic lobule was similar to that in patients with B-CAH but was significantly greater than that in alcoholics with hepatic fibrosis (HF). The CD4/CD8 ratio in the hepatic lobule was low in both alcoholic hepatitis and B-CAH compared with that of alcoholic patients with HF. When Mallory bodies (MB) and lymphocytes were simultaneously stained with a specific antibody against MB and MoAb, respectively, only CD3+ and CD8+ lymphocytes were found to have a close contact with MB. These results suggest that in alcoholic hepatitis, hepatocyte necrosis may be partly mediated by immunological mechanisms involving cytotoxic T cells infiltrating into the hepatic lobule.

Soluble HLA class I antigens in sera of patients with chronic hepatitis

Soluble HLA Class I antigens in sera (serum-HLA Class I, s-HLA Class I) of patients with chronic hepatitis (CH) were measured with an enzyme-linked double determinant immunoassay (E-DDIA). The mean titers of s-HLA Class I antigens of patients with CPH (mean +/- standard deviation, 2.22 +/- 1.60), CAH2A (2.24 +/- 1.65) or CAH2B (2.73 +/- 1.46) were significantly higher than that of normal subjects (0.36 +/- 0.27) (P less than 0.01). The titer of s-HLA Class I correlated significantly with the level of serum glutamic pyruvic transaminase (s-GPT) (r = 0.73), and weakly with serum level of beta 2-microglobulin (r = 0.43). In patients with chronic hepatitis type B (CH-B) treated with human lymphoblastoid interferon alpha (IFN-alpha), the titer of s-HLA Class I antigens increased. The increased level of s-HLA Class I antigens in the clinical course of chronic hepatitis may be caused by their release from necrotizing hepatocytes which have acquired the expression of HLA Class I antigens on the cell-surface membrane during viral infection.

Non specific increased expression of class I major histocompatibility complex (MHC) antigens on rat liver grafts

Major histocompatibility complex (MHC) antigens play a major role in the rejection reaction and their increased expression may increase the host response to the foreign graft. Several clinical and experimental studies have demonstrated increased expression of MHC antigens on the different cell components of liver allografts during rejection. However modified expression of MHC antigens may also occur in certain liver diseases, after cholestasis or on a regenerating liver. In this experimental study in inbred rats, we compared the expression of MHC antigens on liver cells during rejection and non-immunological situations (cholestasis, cytolysis, regeneration).

HCV infection, hepatic HLA display and composition of the mononuclear cell inflammatory infiltrate in chronic alcoholic liver disease

Viral infection may play a role in alcoholic liver disease with histological features of chronic active hepatitis (CAH). Human leucocyte antigen (HLA) hepatocellular display is supposed to allow HLA-restricted T-lymphocyte cytotoxicity in chronic viral hepatitis. We studied the presence of serum anti-hepatitis C virus (HCV) antibodies, the hepatic HLA display and the composition of the mononuclear cell infiltrate in 16 patients with alcoholic liver disease and histological features of CAH and in 11 patients with alcohol-related degenerative changes. All patients were negative for hepatitis B virus (HBV) markers. Anti-HCV were tested by microplate ELISA. Class I HLA A, B, class II HLA DR, lymphocytes pan T, T helper/inducer, T suppressor/cytotoxic, B, and K NK cells were stained on liver cryostat sections by monoclonal antibodies and double indirect immunoperoxidase. Anti-HCV were present in all the patients with features of CAH and absent in those with only degenerative changes. In livers with features of CAH the mononuclear cell infiltrate consisted largely of T lymphocytes with marked prevalence of suppressor/cytotoxic cells in periportal and lobular areas. K NK cells were rare. Class I HLA, diffusely displayed on bile duct epithelium and on sinusoidal cells, also appeared on liver cells in the areas of periportal and lobular necrosis, namely on the hepatocytes in close contact with suppressor/cytotoxic T cells. In livers with only degenerative changes class I HLA were diffusely displayed on bile duct epithelium and on sinusoidal cells but absent on the hepatocytes. In all the specimens HLA DR antigens were expressed on sinusoidal and inflammatory cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Relevance of a positive crossmatch in liver transplantation

We studied 27 liver transplants in 24 patients performed between November 1984 and January 1988. We investigated retrospectively the importance of donor reactive HLA class I and class II and of non-HLA antibodies for graft survival in these patients. In order to determine the specificity and class of the antibodies, we used monoclonal antibodies to HLA-A, -B, -C and DR and DQ antigens to block cytotoxicity of sera and the reagent dithiothreitol to characterize the immunoglobulin class. We found that humoral immunity to HLA antigens in liver-grafted patients, demonstrable as the presence of cytotoxic antibodies reactive with donor splenic T and/or B cells in the pretransplantation period, is associated with significantly lower graft survival as compared with patients without demonstrable preformed HLA antibodies (P = 0.01). In addition we found that a substantial proportion of patients had donor-reactive cytotoxic antibodies which were not HLA specific. Thus, our study shows that HLA immunity can influence liver allograft survival, and that it is useful to have patient cytotoxic antibodies characterized with regard to HLA reactivity prior to transplantation.

Class I and class II major histocompatibility complex antigens on hepatocytes: importance of the method of detection and expression in histologically normal and diseased livers

Methodological differences in major histocompatibility complex (MHC) antigen detection were investigated on isolated, viable hepatocytes and cryostat hepatic sections from 27 children with liver disorders, six of whom had normal histology. Class I antigens were constantly found on sections using a three step immunoperoxidase technique after acetone/chloroform fixation, other techniques being less sensitive, or on isolated hepatocytes by indirect immunofluorescence alone. With mechanical isolation the percentage of positivity ranged from 85 to 100%, while with collagenase isolation it ranged from 22 to 49% on immediate testing, and from 53 to 80% after 24 hour incubation. Class II antigens were only detected in one patient with autoimmune chronic active hepatitis and two with primary sclerosing cholangitis. Flow cytofluorimetric analysis in 11 cases confirmed class II or class I positivity, or both, on isolated hepatocytes, allowing MHC antigen expression on hepatocytes to be measured. Class I and II antigen detection on hepatocytes is influenced by the technique used. Although class I antigens are invariably expressed on hepatocytes, class II antigens are only found on hepatocytes from patients with immune mediated liver disorders.

Class I and class II major histocompatibility complex antigen expression on hepatocytes: a study in children with liver disease

Controversy exists regarding major histocompatibility complex antigen expression on hepatocytes. In this study, hepatocyte expression of class I and II major histocompatibility complex antigens was investigated in diseased and normal livers, using indirect immunofluorescent staining of mechanically isolated, viable hepatocytes. Hepatocytes were obtained from 76 children: 10 with autoimmune chronic active hepatitis, nine with primary sclerosing cholangitis, nine with chronic hepatitis B virus infection, five after liver transplantation, 19 with extrahepatic biliary atresia, 11 with alpha 1-antitrypsin deficiency, four with idiopathic neonatal hepatitis and nine with histologically normal liver. Immunohistochemistry was performed in all cases; flow cytofluorimetry was performed for class I antigens in 38 cases and performed for class II antigens in 18 cases. From three children with autoimmune chronic active hepatitis and two with chronic hepatitis B virus infection, isolated hepatocytes were also incubated with gamma-interferon before staining and analysis. By fluorescence microscopy, class I antigens were detected on hepatocytes from all children, the highest percentage (100%) of positive cells and the most intense staining were observed in untreated patients with autoimmune chronic active hepatitis or primary sclerosing cholangitis and in those with acute rejection of a liver transplant. Reduced class I antigen expression occurred in chronic hepatitis B virus infection. Class II antigens were only detected on hepatocytes from eight patients: three with autoimmune chronic active hepatitis and five with primary sclerosing cholangitis, all untreated. Flow cytofluorimetric analysis confirmed the results obtained by fluorescence microscopy, but it also demonstrated a weak class II antigen expression during liver allograft rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Major histocompatibility complex antigens in human liver transplants

Liver transplantation is performed successfully across major HLA differences between donor and recipient. This may be influenced by the organ specific expression of major histocompatibility complex (MHC) molecules which determine the local immune reactivity and rejection response. The tissue expression of MHC molecules on parenchymal and infiltrating cells has been studied in transplanted human liver using monoclonal antibodies and immunohistological methods. A strong induction of class I (HLA-A,B,C; beta 2-microglobulin) and class II (HLA-DR,DQ,DP) MHC antigens was demonstrated on hepatocytes, bile duct epithelium and endothelial cells during rejection episodes and viral and bacterial infections. The massive induction of donor antigens on hepatocytes, bile ducts and endothelia forms part of, and may also augment, the rejection response. During quiescent states without infection or rejection after transplantation, however, a rather restricted expression of class I and class II donor MHC antigens is present. In addition, the donor Kupffer cells and interstitial dendritic cells are gradually replaced by recipient accessory cells expressing self-MHC molecules. The changes in antigen density and distribution of donor MHC alloantigens as the replacement of accessory cells capable of presenting antigens to T-lymphocytes may influence the course of immune reactivity and the rejection response in the liver. This may partly explain the favourable clinical course long after transplantation. Preliminary clinical investigations of the effect of HLA matching have shown a dualistic effect of the matching of class I or class II HLA antigens. The role of HLA matching in liver transplants in large clinical studies, with specific immunological testing however, remains to be investigated. This may lead to prospective HLA matching with wider organ availability and improved preservation time in the future.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of the MHC antigens after liver transplantation: relationship with biochemical and histological parameters

The aim of this study was to analyse the change in tissue distribution of HLA class I and class II molecules in patients during the course of liver transplantation. Sixty-one liver biopsies were analysed in 24 patients with or without rejection (acute or chronic) episode. In 93% of cases with chronic rejection and in 48% of cases with acute rejection episodes, HLA class I antigens are expressed in the membrane and/or the cytoplasm of hepatocytes. The expression of these molecules was significantly correlated with the ASP (aspartate amino transferase), AP (alkaline phosphatase), the bile duct damage and the centrolobular lesions. In contrast, the expression of HLA class II molecules is not correlated with either the type of rejection, the biological or histological findings. A strong expression of HLA class I antigen on hepatocytes after day 60 may be one of the best signs of chronic rejection.

Immunohistochemical investigation of hepatitis B virus associated antigens, HLA antigens and lymphocyte subsets in type B chronic hepatitis

HLA antigens, hepatitis B virus (HBV)-associated antigens and lymphocyte subsets in liver tissue from 35 patients with HBs antigenemia were studied using an immunoperoxidase double staining method and immunoelectron microscopy in order to clarify the immune mechanism of hepatocyte lysis in type B hepatitis. Immune light and electron microscopy using monoclonal antibodies to lymphocyte subsets revealed that infiltrating lymphocytes in the areas of piecemeal necrosis and focal necrosis were predominantly CD8-positive, showing direct contact with hepatocytes. In contrast, CD4(+) cells were infrequently observed in necrotizing inflammatory lesions. HLA-A,B,C antigens were mainly found on hepatocytes in areas of piecemeal necrosis and focal necrosis, in association with CD8(+) lymphocyte infiltration. HLA-DR antigens were demonstrated on a few hepatocytes in the same lesions. In cases of CAH with serum HBeAg positive, HLA-A,B,C, antigens and HBV antigens simultaneously demonstrated on the same hepatocytes. Especially, hepatocytes expressing both HLA-A,B,C antigen and HBsAg on the plasma membrane showed direct contact with CD8(+)lymphocytes. This finding fulfilled the morphological requirements for HBsAg as a target antigen. On the other hand, HBcAg was hardly demonstrated in the liver cell membrane but was demonstrated mainly in the cytoplasm. Compared with the nuclear localization of HBcAg in cases of NSR, cytoplasmic localization of this antigen may be associated with membranous expression of new antigens induced by HBV infection.

Hepatic expression of class I and class II major histocompatibility complex molecules in primary biliary cirrhosis: effect of ursodeoxycholic acid

Aberrant hepatic expression of HLA molecules has been shown to be present in primary biliary cirrhosis and may play a determining role in the pathogenesis of the disease. We have studied the effect of the long-term administration of ursodeoxycholic acid on hepatic HLA expression. Nine untreated patients with primary biliary cirrhosis, eight patients treated for at least a year with ursodeoxycholic acid and eight control subjects without hepatobiliary disease were compared. HLA expression was studied on liver biopsy sections using a direct immunofluorescence technique with specific monoclonal antibodies directed against class I or class II HLA molecules. Aberrant biliary HLA class II expression was not modified by chronic administration of ursodeoxycholic acid. In contrast, aberrant hepatocyte HLA class I expression was markedly reduced. Reduction in HLA class I expression may lead to decreased cytotoxic T cell-dependent lobular necrosis, which is thought to contribute to the progression of primary biliary cirrhosis to advanced stages. These findings suggest that the beneficial effect of ursodeoxycholic acid treatment in primary biliary cirrhosis could result not only from a reduction in the intrahepatic accumulation of cytotoxic bile acids but also from a reduction in immunological injury.

Ethanol: an enhancer of transplantation antigen expression

Major histocompatibility antigens (MHC) play a pivotal role in the immune response. Abnormal expression of MHC antigens has been correlated with aberrant regulation of the immune response. Studies on the effect of ethanol on class I MHC antigens demonstrate that ethanol significantly enhances their cell surface expression in a variety of cell lines in vitro. These changes in cell surface levels reflect increased intracellular protein synthesis and increased steady state mRNA levels. The effective ethanol concentrations (0.1-1.0%) are physiologically attainable. Measurement of class I MHC antigens on peripheral blood lymphocytes in a population of acutely ethanol-intoxicated patients showed a highly significant increase relative to controls. The possibility that the elevated levels of MHC antigens induced by ethanol may play a role in the evolution of ethanol-related disease is discussed.

Expression of class I and class II major histocompatibility antigens on human hepatocellular carcinoma

Previous reports indicate that human hepatocytes do not express class I and class II MHC antigens. Our analyses on 10 human hepatocellular carcinoma (HCC) cell lines by immunofluorescence tests and RIA, demonstrate that all the human HCC cell lines tested express class I MHC antigens and among them, three poorly differentiated human HCC cell lines also express class II MHC antigens. Results of immunoprecipitation and/or Western blotting experiments indicate similarity in the chemical nature of both the class I and class II MHC antigens expressed by the human HCC cell lines and by a human B lymphoblastoid cell line Raji. Furthermore, a new variant form of class I antigen was detected in some of these HCC cell lines. Immunohistochemical studies of HCC tissues using the peroxidase-antiperoxidase staining method indicated that class I and class II antigens were detectable in 7 out of 11 and 3 out of 11 HCC tissues from patients, respectively. The availability of MHC class I antigen-positive cultured HCC cell lines, including the poorly differentiated lines that also express MHC class II antigen, has provided us with interesting models to study the relationship between expression of MHC antigen and transformation and differentiation of human hepatocytes. These studies will also allow us some insight into the role of MHC class I and class II antigen in the immunosensitivity and immunogenicity of HCC cells to the host-immune response.

Alcohol, cancer, and immunomodulation

There is a great deal of epidemiological evidence indicating that chronic, excessive alcohol consumption is a major risk factor for cancers in humans. However, the experimental basis for the increased cancer risk associated with alcohol intake is not clear. Since it appears that ethanol alone is not carcinogenic, ethanol effects must be explained in terms of its modifying the actions of other causal agents. Current studies indicate that ethanol and its congeners may act as tumor promoters, thereby enhancing the effect of initiating carcinogens from the environment. Available evidence also shows that ethanol is immunosuppressive. Clearly, cirrhosis due to high, prolonged alcohol intake is an indicator of the immunosuppressive effects of ethanol. It is less clear that more moderate intakes of alcohol could have as profound an effect on immune systems. However, changes do occur yielding alterations in lymphocyte sensitivity to alcohol in vitro and in cell development, as shown by increased NK cell function at low concentrations. Since other conditions, such as cytotoxic drugs which suppress cellular immune functions, are clearly associated with increased cancer risk. It is intriguing to think that prolonged exposure to ethanol-induced immunosuppression may be a cofactor in the promotion of cancer. The tumor promotion may take place via a variety of mechanisms as discussed in this paper, including reduced host defenses by direct effects of ethanol, its metabolites, and/or malnutrition. It may be beneficial to test methods for immunostimulation in prolonged alcohol abusers, where cessation of use is unsuccessful or residual immunosuppression remains, to reduce the risk of development or growth of initiated tumors.

Evidence of increased class I MHC expression on human peripheral blood lymphocytes during acute ethanol intoxication

Certain ethanol-related diseases in humans have been linked to disorders of immunity. Although humoral and cellular immunity have been studied, the precise mechanisms whereby ethanol use leads to tissue damage remain unknown. In order to explore the hypothesis that ethanol may lead to alteration in expression of tissue Class I major histocompatibility antigen causing an autoimmune phenomenon, a population of acutely ethanol-intoxicated patients was studied. Measurement of Class I major histocompatibility antigen on peripheral blood lymphocytes in this population showed a highly significant (p less than 0.01) increase over controls. The role that this increased antigenicity may play in the evolution of clinical disease is discussed.

Biliary beta 2-microglobulin in liver allograft rejection

beta 2-Microglobulin, which is associated with HLA class 1 antigens, was assayed in bile and serum from 19 patients following 22 liver transplants. Serum levels were elevated in all posttransplant patients irrespective of the presence of rejection. In contrast, biliary levels were significantly higher during episodes of acute rejection compared with posttransplant cholangitis (p less than 0.01), stable graft function (p less than 0.0001) and nontransplant samples (p less than 0.0001). When bile/serum ratios were studied, the difference between the rejection and the other groups was even more significant, and if a ratio of 0.2 was considered diagnostic of rejection, the test had a sensitivity of 96%, a specificity of 87% with an accuracy of 90%. Therefore, these results suggest that the measurement of bile/serum ratios of beta 2-microglobulin following liver transplantation may be useful in diagnosing acute rejection. When bile/serum ratios of beta 2-microglobulin were compared with those for other proteins, there was strong evidence to suggest that local release accounted for most of the increased biliary beta 2-microglobulin during rejection. These results provide further evidence that HLA class 1 antigens on the biliary epithelium may be important in liver allograft rejection.

Beta-2-microglobulin expression in the liver after liver transplantation

The distribution of major histocompatibility complex (MHC) class 1 antigens was studied in the liver after transplantation by immunoperoxidase staining for beta-2-microglobulin (beta 2m), a subunit of the class 1 antigen system. Paraffin wax sections were examined from 25 "time zero" biopsy specimens, taken immediately after insertion of the graft, and 87 biopsy specimens taken after transplantation in seven diagnostic categories: acute cellular rejection (n = 22); resolving acute rejection (n = 8); chronic rejection (n = 22); pure cholestasis (n = 14); ischaemia/infarction (n = 5); biliary obstruction (n = 8); massive haemorrhagic necrosis (n = 8). Staining was graded semiquantitatively on a scale of 0-3+ in bile ducts, hepatocytes, sinusoidal lining cells and vascular endothelium. Using the "time zero" biopsy specimens as a baseline for comparison, increased expression of beta 2m was seen in bile ducts, hepatocytes, and endothelial cells after transplantation. These changes were most pronounced in cases of rejection but also occurred in other graft conditions. The degree of hepatocyte and endothelial staining was significantly higher in cases of rejection and massive haemorrhagic necrosis than in the other categories. These findings may have implications for the pathogenesis and diagnosis of rejection of the transplanted liver.

Early induction of MHC antigens in human liver grafts. An immunohistologic study

The present study documents major histocompatibility complex (MHC) Class I and II expression during early acute rejection of human liver grafts. Serial graft biopsies (pretransplant, time zero, and 1 week) were studied. Ten patients received azathioprine (AZA) and prednisone; the other six patients were treated with quadruple therapy (azathioprine, cyclosporine A, prednisone, and cyclophosphamide). To study the specificity of changes in MHC antigen expression, biopsies of six patients with minor or no morphologic abnormalities served as controls. In addition, phenotypes of inflammatory cells present during rejection were analyzed using a panel of monoclonal antibodies. The results show that during acute rejection expression of MHC Class I and II antigens increased significantly in the AZA-treated patients, in a pattern similar to that seen in the patients treated with quadruple therapy, showing enhanced MHC Class I expression on hepatocytes, bile duct epithelium, and sinusoidal endothelium, and Class II antigen on Kupffer cells and sinusoidal endothelium. Bile duct epithelium was consistently positive for Class II antigen; no significant difference with the nonrejection group was observed. T cells are the predominant inflammatory cells during rejection with equal quantities of CD4+ and CD8+ cells. A majority of the infiltrating T cells show expression of Class II antigen but do not react with anti-interleukin-2 receptor antibody. This may be the result of immunosuppressive therapy or a simple reflection of the temporary expression of interleukin-2 receptors during lymphocyte activation. The authors hypothesize that the induction of MHC antigens on bile duct epithelium leads to rejection whereas the expression on hepatocytes represents an epiphenomenon.

HLA class I antigen display on hepatocyte membrane in chronic hepatitis B virus infection: its role in the pathogenesis of chronic type B hepatitis

It has been suggested that cytotoxic T cells are involved in the recognition and lysis of the infected hepatocytes in chronic hepatitis B virus infection, and that the target antigen is probably HBcAg which is displayed on the hepatocyte membrane during active viral replication. However, studies in other viral infection have demonstrated that cytotoxic T cells recognize viral antigen on the infected cells only in the context of HLA class I antigens. To test whether this mechanism is also operative in chronic hepatitis B virus infection, we studied the expression of HLA class I antigens in livers from 35 patients with chronic hepatitis B virus infection by indirect immunofluorescence using monoclonal antibody against HLA class I antigens. The blocking effect of monoclonal antibody against HLA class I antigens on the in vitro T cell cytotoxicity to autologous hepatocytes was also studied. The results revealed that HLA class I antigen was undetectable on the hepatocyte membrane in all of 10 HBeAg-positive carriers with minor hepatitic activity, whereas it was demonstrated in 15 (88%) of the 17 HbeAg-positive patients with chronic active liver disease and in 7 (87%) of the 8 anti-HBe-positive "normal" carriers. The in vitro T cell cytotoxicity to autologous hepatocytes in six HBeAg-positive patients with chronic active liver disease was significantly inhibited by preincubation of hepatocytes with monoclonal antibody (10 to 40 micrograms per ml) against HLA class I antigen, but not by monoclonal antibody against HLA class II antigens and non-HLA-associated surface molecules (Leu 11).(ABSTRACT TRUNCATED AT 250 WORDS)