Transferrin receptor expression in rat liver: immunohistochemical and biochemical analysis of the effect of age and iron storage

Hepatic transferrin receptors were studied in normal male rats at 1 to 59 wk after weaning, using immunohistochemical and biochemical techniques. The number of transferrin receptors measured and the intensity of the staining in situ decreased rapidly during the first 10 wk of life and more slowly thereafter. Immunohistochemistry further demonstrated changes in the topographical and (sub)cellular localization of the transferrin receptor. In the young rat livers, staining was almost exclusively present on hepatocytes in acinar zone 2 + 3 in a honeycomb to sinusoidal pattern. With aging, a panacinar heterogeneous and mainly sinusoidal staining of hepatocytes was more frequent. Kupffer cell positivity was more obvious as compared with the young rat livers. The observed changes in transferrin receptor expression may partly be explained by age-dependent alterations in DNA synthesis and proliferative potential of the liver cells. A series of rats were iron loaded with carbonyl iron up to 39 wk and "unloaded" by administration of a normal diet during 20 wk. In these animals, serial histochemical studies showed predominantly parenchymal (7 to 14 wk), mixed parenchymal and reticuloendothelial (39 wk) and almost exclusive reticuloendothelial siderosis (59 wk). In the siderotic livers transferrin receptor numbers tended to be lower than in the controls with significant differences after 14 and 39 wk. Immunohistochemistry showed decreased parenchymal but increased reticuloendothelial transferrin receptor expression with iron load. After the period of unloading, parenchymal transferrin receptors were virtually absent despite the negligible siderosis of these cells. In contrast, siderotic reticuloendothelial cells were intensely positive. These findings support down-regulation of parenchymal transferrin receptor resulting from iron storage. However, the positivity of siderotic reticuloendothelial cells and the absence of re-emergence of parenchymal receptors in conditions of minimal parenchymal and prominent reticuloendothelial siderosis need further elucidation.

Differential diagnosis and prognosis of cirrhosis: role of liver biopsy

Histopathological examination of needle biopsies of the liver is a cornerstone in the diagnostic work-up on a patient with symptoms of chronic liver disease. It allows to confirm whether cirrhosis is present or not. In a considerable number of cases, this confirmation is definitive. In some cases, only a diagnostic level of suspicion is reached. In these cases, close collaboration between clinician and pathologist may increase the degree of diagnostic certainty. A reliable diagnosis of cirrhosis on liver biopsies requires careful consideration of differential diagnostic alternatives. Application of the full battery of histopathological techniques, including special stains, polarizing light and immunohistochemistry, allows to specify (or to help to specify) the aetiology in a substantial number of cases. The histopathologist should further look for information which bears on prognosis, and evaluate the stage, the activity and eventual complications by search of the corresponding histological changes.

Transferrin receptor expression in benign tumours and in hepatoblastoma of the liver

To further investigate the possible usefulness of antitransferrin receptor staining in the differential diagnosis between benign and malignant primary liver tumours, we examined the transferrin receptor expression in ten cases of focal nodular hyperplasia, six of nodular regenerative hyperplasia, two adenomas and six hepatoblastomas. In focal nodular hyperplasia, the ductular structures were always positive and the parenchymal cells displayed three staining patterns of moderate intensity. In nodular regenerative hyperplasia there was scattered, relatively weak transferrin receptor staining. The tumour cells in the adenomas were only weakly positive. Three hepatoblastomas showed an intense staining of tumour cells; one was weakly positive and two were negative. A high intensity of transferrin receptor staining, as previously described in hepatocellular carcinomas, was only observed in the hepatoblastomas. This gives further credence to the usefulness of strong transferrin receptor expression in evaluating the malignant nature of tumour foci in liver biopsies.

A cytokeratin-immunohistochemical study of focal nodular hyperplasia of the liver: further evidence that ductular metaplasia of hepatocytes contributes to ductular "proliferation"

A cytokeratin-immunohistochemical study was performed on eight specimens of focal nodular hyperplasia of the liver in order to determine whether hepatocytes in this lesion can express "bile duct type" cytokeratins. Serially cut cryostat sections were reacted with a panel of six monoclonal antibodies specifically reactive with cytokeratin polypeptides nr. 7, 8, 18 and 19, using a 3-step immunoperoxidase procedure. Hepatocytes were positive for cytokeratins nr. 8 and nr. 18, whereas ductules contained in addition to cytokeratins nr. 8 and nr. 18 also polypeptides nr. 7 and nr. 19. In all cases, a variable number of hepatocytes close to fibrous septa or inside the nodules expressed cytokeratin nr. 7. In four cases, a small number of hepatocytes were also immunoreactive for cytokeratin nr. 19. Our data demonstrate that hepatocytes in focal nodular hyperplasia can express one or even two "bile duct type" cytokeratins, supporting the concept that ductular metaplasia of hepatocytes contributes to the ductular "proliferation" observed in this tumor-like lesion.

A cytokeratin immunohistochemical study of cholestatic liver disease: evidence that hepatocytes can express 'bile duct-type' cytokeratins

A cytokeratin immunohistochemical study was performed on 38 liver biopsies from cases of primary biliary cirrhosis, primary sclerosing cholangitis, extrahepatic biliary obstruction or drug-induced liver disease in order to analyse the cytoskeletal changes in detail. On paraffin sections of 27 cases, a variable number of hepatocytes were reactive with a polyclonal anti-cytokeratin antiserum that, in the normal liver, stains bile duct cells only. On cryostat sections of 23 cases, a variable number of hepatocytes were immunoreactive with a monoclonal antibody specifically directed against cytokeratin no. 7 and were most numerous in cases of long-standing cholestasis irrespective of the aetiology. In three cases of primary sclerosing cholangitis and two cases of primary biliary cirrhosis a few hepatocytes were also weakly positive with a monoclonal antibody specific for cytokeratin no. 19. Since cytokeratins no. 7 and no. 19 are, in the normal liver, restricted to bile duct cells, these results further support the concept of 'ductular metaplasia' of hepatocytes, the mechanism of which remains unclear.

In situ localization of melanotransferrin (melanoma-associated antigen P97) in human liver. A light- and electronmicroscopic immunohistochemical study

Using an indirect immunoperoxidase technique on frozen sections with the monoclonal antibody 96.5, we investigated the in situ distribution of melanotransferrin, a transferrin (Tf) and transferrin receptor (TfR) related glycoprotein, in human liver. Specimens included normal liver, liver in iron overload, hepatocellular carcinoma, angioma and foetal liver. On light microscopy, immunoreactivity was almost exclusively present on sinusoidal lining cells, apparently endothelial cells; the pattern was similar in normal and in iron-loaded liver. A gradient of more enhanced staining in acinar zone II and III was observed. The endothelial localization of the staining was supported by the positivity of the central vein endothelium and of the angiomas. Immunoelectron microscopy on three liver specimens showed positivity on sinusoidal endothelial cells but not on Ito and Kupffer cells. In addition, positivity on rough endoplasmic reticulum vesicles of some hepatocytes was also present. Four hepatocellular carcinomas showed an intense staining in tumour cells, 3 were weakly positive and 3 were negative. In the foetal livers, the central vein endothelium was positive from 21 weeks of gestation onward and additional positivity of zone III sinusoidal endothelial cells was present from 27 weeks on. The present results show that in the liver melanotransferrin has a localization different from Tf and the TfR. These latter molecules are predominantly localized in parenchymal cells. In addition, there does not appear to be a coordinate regulation secondary to iron storage, between melanotransferrin, Tf and the TfR. The observed gradient in the staining pattern in foetal and adult liver specimens further supports the heterogeneity of the endothelial cell population in the liver and suggests a developmental relationship between endothelial cells of sinusoids and central vein.

Hepatocellular transferrin receptor expression in secondary siderosis

We investigated the hepatocellular transferrin receptor expression in 55 human liver specimens with secondary siderosis, with an indirect immunoperoxidase technique on frozen sections using 3 monoclonal anti-transferrin receptor antibodies. For comparison, specimens were also stained with the monoclonal antibody BK19.9, recognizing an antigen which is biochemically similar to the transferrin receptor, and with a monoclonal antibody against the epidermal growth factor receptor. The degree of iron overload was estimated semi-quantitatively, taking into account hepatocellular and Kupffer cell iron deposition. In 47 out of 55 specimens hepatocellular transferrin receptor expression was present. The positivity was predominantly localized on hemosiderin-free hepatocytes. With increasing hepatocellular iron deposition, the proportion of cases with absent transferrin receptor immunoreactivity increased. This supports the previously reported disappearance of hepatocellular transferrin receptor expression in primary hemochromatosis cases with severe iron deposition. However, the transferrin receptor negative cases included four specimens in which Kupffer cell iron deposition clearly exceeded hepatocyte iron load. This finding suggests that in addition to hepatocellular iron load other factors may regulate the expression of parenchymal transferrin receptors in iron overload diseases. These may include plasma levels of various iron sources and/or Kupffer cell iron load. The iron deposition did not influence the staining of the hepatocellular epidermal growth factor receptor nor the Kupffer cell staining by the BK19.9 antibody. This confirms the specificity of the findings concerning the behaviour of the transferrin receptor in secondary siderosis.

Incomplete septal cirrhosis: histopathological aspects

We have reviewed 60 liver specimens from 47 patients with the diagnosis of incomplete septal cirrhosis observed between 1968 and 1987. In reaching this diagnosis evaluation of the following histological features appeared to be helpful: parenchymal nodularity, thin incomplete septa, hypoplastic portal tracts, increased number of venous channels, abnormal spacing between portal tracts and veins, crowding of reticulin fibres between adjacent zones of hyperplastic parenchyma, hyperplasia of hepatocytes and dilated sinusoids. These histological features were not specific for incomplete septal cirrhosis as they were also present--although less evident and less frequent--in a series of 87 non-cirrhotic liver specimens. Reticulin stains were an essential adjunct to assess the architectural disturbance, which was often inconspicuous in needle biopsies. Histological features indicating a specific aetiology were lacking in the great majority of cases. On histological and clinical grounds, incomplete septal cirrhosis resembles idiopathic portal hypertension, nodular regenerative hyperplasia and partial nodular transformation; in these entities an obliterative portal venopathy with non-uniformity of portal blood supply to the parenchyma has been suggested as a pathogenic mechanism. In the present study phlebosclerotic lesions of the portal vein were found in only two cases. This might be explained by sampling error or, alternatively, the hypoplastic portal tracts observed might be a functional equivalent of obliterative portal venopathy resulting in a deficient portal blood supply. Non-uniformity of blood supply to the parenchyma may explain the similarities between incomplete septal cirrhosis and the diseases mentioned.

A cytokeratin immunohistochemical study of alcoholic liver disease: evidence that hepatocytes can express 'bile duct-type' cytokeratins

A cytokeratin immunohistochemical study was performed on 40 liver biopsies diagnosed as alcoholic liver disease to further investigate the cytoskeletal changes occurring in this disease. On paraffin sections of 29 cases, a variable number of hepatocytes were reactive with a polyclonal antiserum that normally stains only bile ducts. Using monoclonal antibodies specific for a single cytokeratin polypeptide on cryostat sections, a variable number of hepatocytes were immunoreactive for cytokeratin no. 7 in 23 cases and also for cytokeratin no. 19 in seven cases. Both these polypeptides are restricted to bile duct cells in the normal liver. The number of hepatocytes positive for bile duct-type cytokeratins increased and their location changed with the severity of the disease. Mallory bodies were reactive with monoclonal antibodies CAM 5.2 and anti-cytokeratin no. 18 but unreactive with anti-cytokeratin no. 8. except in one case. In two cases, Mallory bodies reactive with both monoclonal antibodies anti-cytokeratin no. 7 and anti-cytokeratin no. 19 were found. These results clearly indicate that hepatocytes in alcoholic liver disease can express immunoreactivity for bile duct-type cytokeratins. Our data also demonstrate heterogeneity in the composition of Mallory bodies. Whether hepatocytes expressing bile duct-type cytokeratins are the precursors of Mallory body-containing cells is not clear at present.

Immunoelectron microscopic localization of hepatic transferrin receptors in human liver with and without iron overload

The expression of transferrin receptors (TfR's) has been investigated in eight liver biopsy specimens (four from patients without demonstrable iron and four from patients with iron storage due to primary hemochromatosis (HC)) using immunoelectron microscopy to demonstrate TfR's by the simultaneous application of two specific monoclonal antibodies (OKT9 and B3/25) to tissue chopper sections. In the four specimens without iron overload, hepatocytes, but not sinusoidal lining cells, stained positively and immunoreactivity was mainly localized in the cytoplasm. Positively stained cisternae of the endoplasmic reticulum indicated synthesis of the TfR. The presence of TfR's on segments and coated invaginations of the sinusoidal membrane and in small, but otherwise unidentified vesicles in the cytoplasm is compatible with endo-/exocytotic transport and recycling of TfR's as demonstrated by biochemical studies. Occasional positively stained material in canalicular lumina together with positively stained canalicular microvilli and pericanalicular vesicles suggest that transcellular transport may be an additional pathway for TfR's. In three biopsies showing severe iron overload due to HC, TfR immunoreactivity was completely absent. The remaining specimen showing HC, exhibited relatively mild iron overload and showed only a few positively stained hepatocytes. This supports the previously reported disappearance of hepatic TfR expression in HC when iron overload is severe.

The development of the intrahepatic bile ducts in man: a keratin-immunohistochemical study

The development of the intrahepatic bile ducts in man was studied using an immunohistochemical technique on 56 liver specimens ranging in age from 6 weeks of gestation to 8 months after birth. On paraffin sections, two monoclonal anticytokeratin antibodies (CAM 5.2 and KL-1) that normally stain both hepatocytes and bile duct cells and two polyclonal anticytokeratin antisera that in normal adult liver stain bile ducts only were applied. For immunohistochemical staining of cryostat sections (only available from 14 weeks of gestation on), four monoclonal antibodies specifically directed against individual cytokeratin polypeptides 7,8, 18 and 19 were used. Adult human hepatocytes contain cytokeratin 8 and 18 whereas bile duct cells also express cytokeratin 7 and 19 in addition to cytokeratin 8 and 18. On paraffin sections, primitive hepatocytes were stained with monoclonal antibodies CAM 5.2 and KL-1 from 6 weeks of gestation on. On cryostat sections, they were positive with monoclonal antibodies anticytokeratin 8 and 18 from the earliest time point examined (14 weeks). From 9 weeks of gestation on, portal vein branches were surrounded by a layer of cells showing a stronger positive reaction with monoclonal antibodies CAM 5.2 and KL-1 on paraffin sections and with monoclonal antibodies anti-cytokeratin 8 and 18 on cryostat sections (only available from 14 weeks on). This layer, referred to as the ductal plate, first appeared around large portal vein branches close to the hilum and subsequently around more peripheral branches. The duct plates became duplicated over variably long segments of their perimeter, lumina appeared and tubular structures were formed. The latter gradually became incorporated in the connective tissue surrounding the portal vein, resulting in the appearance of individualized bile ducts. Ductal plate cells were stained by both polyclonal anticytokeratin antisera on paraffin sections. On cryostat sections (available from 14 weeks of gestation on), they were immunoreactive for cytokeratin 19 but negative with the monoclonal antibody directed against cytokeratin 7 until 20 weeks of gestation. From then on, weakly positive staining for cytokeratin 7 was detected, but staining intensity subsequently increased and reached the level observed in adult liver at 1 month after birth. At birth, the smallest branches of the portal vein were still surrounded by a discontinuous ductal plate. We conclude that intrahepatic bile duct cells develop from hepatocytes around branches of the portal vein.(ABSTRACT TRUNCATED AT 400 WORDS)

Intrahepatic bile duct development in the rat: a cytokeratin-immunohistochemical study

The development of the intrahepatic bile ducts was studied in rats from day 12 of gestation until 10 days of age using three antibodies directed against cytokeratins in an immunohistochemical procedure on paraffin-embedded liver tissue. In adult rat liver, both hepatocytes and bile ducts were stained by the monoclonal anti-cytokeratin no. 8, whereas two polyclonal antibodies stained bile ducts only. Hepatocytes in developing rat liver were stained by monoclonal anti-cytokeratin no. 8 from day 12 of gestation on. On day 16, cells strongly immunoreactive for cytokeratin no. 8 were observed in a string of pearl-like arrangement around large vascular branches close to the liver hilum. Over the following days, similar structures appeared throughout the liver. Gradually, lumina were formed in these structures, again starting at the liver hilum and resulting in the formation of individual bile ducts. Immunoreactivity with the polyclonal antibodies was first detected in some of the string of pearl-like structures on day 19 and gradually increased until the intensity observed in adult rat liver was reached on day 1 after birth. Even on day 10, portal spaces still revealed more bile duct branches, rings of cells strongly positive for cytokeratin no. 8 and weakly positive with the polyclonal antibodies were present. It is concluded that the intrahepatic bile ducts develop from hepatocytes. The cells closest to large vascular spaces first become strongly positive for cytokeratin no. 8 and only later on acquire additional ("bile duct type") cytokeratins. This process starts at the liver hilum and spreads through the liver. Even at 10 days of age the bile duct system is still immature: around the smaller portal vein branches, rings of cells are still undergoing transformation into bile duct type cells. These data might be useful for reevaluation of pathologic phenomena.

Cytokeratin expression in hepatocellular carcinoma: an immunohistochemical study

Normal human hepatocytes express cytokeratins no. 8 and 18, whereas bile duct cells contain the same cytokeratins and, in addition, cytokeratins no. 7 and 19. This cytokeratin pattern is believed to be preserved during neoplastic transformation. Thirty-four cases of hepatocellular carcinoma (11 well differentiated, 16 moderately differentiated, 7 poorly differentiated) were studied on frozen sections using monoclonal antisera directed against individual cytokeratins no. 7, 8, 18, and 19 in an immunoperoxidase procedure. In 17 of 34 cases, tumor cells showed only reactivity with monoclonals anticytokeratin no. 8 and 18. However, 17 of 34 cases showed an aberrant pattern in that a variable number of tumor cells were stained with anticytokeratins no. 7 and/or 19 in addition to no. 8 and 18. Only three of 11 well-differentiated cases displayed an unexpected cytokeratin pattern, whereas an aberrant pattern was present in all seven of seven poorly differentiated cases. These results are in conflict with previously published data obtained by two-dimensional gel electrophoresis and immunohistochemistry. They indicate that the cytokeratin pattern might not always be preserved during neoplastic transformation. The implication of this finding for the differential diagnosis of metastatic gastrointestinal carcinomas is discussed.

HLA expression in human hepatocellular carcinoma

This study examines the expression of MHC class I and II antigens and their related invariant chains in 70 cases of human hepatocellular carcinoma (HCC), using monoclonal (Mabs) and polyclonal antibodies. In comparison with normal hepatocytes, the majority (94.3%) of HCCs show enhancement or acquisition of HLA-A, B, C in either a cytoplasmic or membranous distribution, with staining being uniformly distributed throughout the specimen. HLA-A, B, C was accompanied by beta 2-microglobulin expression in all but two cases. Although 44.9% of specimens showed HLA-DR expression, positively staining tumour cells were often sparse and heterogeneously distributed. By contrast, the invariant (I) chain, present in 47.1% of cases, was frequently intensively stained and extensive in distribution. HLA-DR staining was usually cytoplasmic although two cases showed faint membranous enhancement. In addition to HLA-DR and I-chain, two cases also showed HLA-DQ staining. Display of MHC antigens was not related to tumour differentiation or size of the lesion (resected vs. advanced tumours). It is possible that the acquisition of class I antigens by the majority of HCCs may influence tumour behaviour.

HLA expression in human hepatocellular carcinoma

This study examines the expression of MHC class I and II antigens and their related invariant chains in 70 cases of human hepatocellular carcinoma (HCC), using monoclonal (Mabs) and polyclonal antibodies. In comparison with normal hepatocytes, the majority (94.3%) of HCCs show enhancement or acquisition of HLA-A, B, C in either a cytoplasmic or membranous distribution, with staining being uniformly distributed throughout the specimen. HLA-A, B, C was accompanied by beta 2-microglobulin expression in all but two cases. Although 44.9% of specimens showed HLA-DR expression, positively staining tumour cells were often sparse and heterogeneously distributed. By contrast, the invariant (I) chain, present in 47.1% of cases, was frequently intensively stained and extensive in distribution. HLA-DR staining was usually cytoplasmic although two cases showed faint membranous enhancement. In addition to HLA-DR and I-chain, two cases also showed HLA-DQ staining. Display of MHC antigens was not related to tumour differentiation or size of the lesion (resected vs. advanced tumours). It is possible that the acquisition of class I antigens by the majority of HCCs may influence tumour behaviour.

Transferrin receptor expression in human hepatocellular carcinoma: an immunohistochemical study of 34 cases

Using a panel of five monoclonal anti-transferrin receptor antibodies, we investigated the transferrin receptor expression in 34 human hepatocellular carcinomas of Belgian (n = 6), Italian (n = 7) and South African (n = 21) origin. For comparison the tumours were also stained with the monoclonal antibody BK 19.9, recognizing an antigen biochemically similar to the transferrin receptor, and with a monoclonal antibody against the epidermal growth factor receptor. Hepatocellular carcinomas express large amounts of transferrin receptors as demonstrated by the intense transferrin receptor immunostaining in 33/34 cases. Differences in staining pattern between and within the tumours were not related to the degree of tumour differentiation, nor to the origin or race of the patient. In 15 cases which included non-tumoural tissue, the tumour was more intensely stained than the surrounding liver parenchyma. The BK 19.9 immunoreactivity was generally weaker and mainly involved stromal cells, except in three cases where an intense staining of the tumour cells was seen. The epidermal growth factor receptor staining was also weaker and only in four cases was the immunoreactivity of the tumour stronger than the surrounding parenchyma. Demonstration of the transferrin receptor may be useful for the detection of malignant foci in liver biopsies. This may be of particular interest in the histological investigation of minute hepatocellular carcinomas.

Lack of hepatic transferrin receptor expression in hemochromatosis

The major part of hepatocellular iron is derived from uptake of transferrin-bound iron by means of nonspecific fluid-phase endocytosis and specific, saturable binding on high-affinity transferrin receptors. We investigated the expression of transferrin receptors on hepatocytes in liver biopsies of 22 cases of hemochromatosis (21 primary hemochromatosis and 1 secondary hemochromatosis), using immunohistochemical demonstration of the human transferrin receptor with the specific monoclonal antibody OKT9. Fifty liver biopsies (normal and pathological) without demonstrable iron storage (Perls' stain negative) served as controls. In the controls, membranous and/or cytoplasmic transferrin receptor expression was always present on hepatocytes, albeit in variable numbers and patterns without obvious relation to the underlying liver disease. In 19 of 22 hemochromatosis cases with severe iron overload, OKT9 immunoreactivity on hepatocytes was completely absent. Three hemochromatosis cases showed few hepatocytes positive for OKT9. One showed mild iron overload, while the second, a successfully treated case, was free of iron. The remaining hemochromatosis case was a known alcoholic with severe iron overload. Since OKT9 binding to the transferrin receptor is not blocked by previous binding of transferrin, the findings show that in advanced hemochromatosis hepatocytes do not express transferrin receptors. This finding is in keeping with the inverse relation between transferrin receptor expression and exogenous iron supply in various cell cultures. These results indicate that in hemochromatosis,apparently as a result of progressive iron overload,transferrin receptor expression on hepatocytes disappears.(ABSTRACT TRUNCATED AT 250 WORDS)

Keratin immunohistochemistry in normal human liver. Cytokeratin pattern of hepatocytes, bile ducts and acinar gradient

A panel of 2 polyclonal and 7 monoclonal antibodies directed against cytokeratins was tested on cryostat and paraffin sections of 14 normal human liver biopsies using an immunoperoxidase procedure. The staining characteristics of hepatocytes and bile ducts are reported. On cryostat sections, monoclonal antibodies directed against individual cytokeratins no. 8 and no. 18 stained both bile ducts and hepatocytes, whereas monoclonals anti-cytokeratin no. 7 and no. 19 exclusively stained bile ducts. The potential use of these 4 monoclonal antibodies in liver histopathology is briefly discussed. Monoclonal antibody anti-type II cytokeratins and the polyclonal rabbit anti-human keratin stained only bile ducts on both cryostat and paraffin sections. Using monoclonal antibody CAM 5.2 on paraffin sections, both bile ducts and parenchyma were positive. An acinar gradient was apparent in that zone 1 hepatocytes were more intensely stained. Moreover, a rim of hepatocytes around terminal hepatic venules and adjacent to subhepatic veins showed more intense staining. The same gradient could be seen in some paraffin sections stained with the monoclonals anti-cytokeratin no. 18 and KL1, and the rabbit polyclonal anti-keratin "wide spectrum screening". The gradient is interpreted as reflecting quantitative differences in keratin content between hepatocytes. Polyclonal rabbit anti-human keratin is proposed as the most reliable antibody for identification of bile ducts in paraffin sections. The usefulness of reliable bile duct staining in several pathological conditions is emphasized.

In situ characterisation of the (peri)portal inflammatory infiltrate in acute hepatitis A

The portal and acinar zone 1 (periportal) inflammatory infiltrate in acute hepatitis A (HA) strongly resembles piecemeal necrosis (PMN) in chronic hepatitis B (HB). The latter infiltrate has been characterized in detail previously, and a predominance of suppressor/cytotoxic T cells has been demonstrated. For comparison we analyzed the infiltrate in acute HA in three liver biopsies, applying a broad panel of monospecific and monoclonal antibodies. In two cases, helper/inducer T cells surrounded by B lymphoid cells represented the main lymphoid subset in all portal areas. In the third liver biopsy, a case of acute HA superimposed on a pre-existing chronic HB, the cellular composition of the inflammatory infiltrate varied from one portal tract to another. Despite the morphological resemblance between the inflammatory infiltrate in acute HA and PMN in chronic HB, a clear-cut difference in the composition of both infiltrates is obvious from our results. By virtue of the presence of numerous suppressor/cytotoxic T cells, PMN in chronic HB represents the morphological expression of a cellular immune response, whereas the predominance of helper/inducer T cells, admixed with B cells and plasma cells in acute HA represents the morphological expression of a humoral immune response.

Hepatitis A: a Kupffer cell disease?

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Expression of MHC products by normal and abnormal bile duct epithelium

Using antibodies directed to beta 2-microglobulin (b2-m) and HLADR antigens, the expression of MHC products by normal and abnormal bile ducts in 90 paraffin-embedded biopsies showing various liver diseases, was studied. Normal and abnormal bile ducts constantly expressed b2-m. Increased b2-m expression was found in 17/19 PBC, and 4/7 chronic aggressive hepatitis or cirrhosis of viral etiology with hepatitic bile duct lesions. Normal bile ducts failed to express HLADR antigens. Aberrant HLADR display was found in 24/26 PBC and 10/16 chronic aggressive hepatitis or cirrhosis of viral etiology with hepatitic bile duct lesions. It is concluded that the pattern of the major histocompatibility complex (MHC) display does not discriminate between PBC and hepatitic bile duct lesions. Enhanced expression of class I MHC products at the surface of medium-sized bile ducts in PBC may render these structures more susceptible to lysis by cytotoxic T-cells, whereas its significance in chronic aggressive hepatitis or cirrhosis remains unknown. Aberrant expression of HLADR antigens by abnormal bile ducts in PBC and chronic aggressive hepatitis or cirrhosis of viral etiology is probably induced by gamma-interferon, liberated by intra-epithelial lymphocytes, and may serve to enhance the immune response, either by attracting HLADR-restricted cytotoxic T-cells or by the presentation of non-self antigens at the surface of bile duct epithelium.

Cholestatic features in hepatitis A

The clinical, biochemical and histological characteristics of 13 cases of acute hepatitis A were evaluated. In 10 biopsies moderate to severe cholestasis was seen consisting of bile thrombi, cholestatic liver cell rosettes and ductular transformation of hepatocytes as shown on keratin- and S-100 immunostaining. The periportal spotty necrosis may play a role in the pathogenesis of cholestasis in hepatitis A by creating an interruption in continuity of bile flow. In 6 cases, abnormal ductular epithelium was seen resembling the ductular lesion in septicemia. Such ductular lesion may be related to the accumulation of leucotrienes as a result of cholestasis.