Expression of Ia-antigens on guinea pig Kupffer cells. Studies with monoclonal antibodies

Accumulation and cellular localization of fibrinogen/fibrin during short-term and long-term rat liver injury

BACKGROUND/AIMS

During liver fibrosis, there is a putative pacemaker role of fibronectin. Fibrinogen is closely linked to fibronectin during clotting processes. The aim of this study was to show fibrinogen gene expression during liver damage.

METHODS

Fibrinogen/fibrin deposition in damaged livers was studied by immunohistology. Fibrinogen gene expression was analyzed in vivo in a model of CCl4-induced rat liver damage and in vitro in isolated liver cells by means of Northern blot analysis and in situ hybridization.

RESULTS

Immunohistology showed striking amounts of fibrinogen and fibrin deposits in pericentral necrotic areas (short-term damage) and within fibrotic septa (long-term damage). Total RNA extracted from short-term-damaged livers contained an increased fibrinogen messenger RNA level. By in situ hybridization, fibrinogen transcripts were localized in cells of the nonnecrotic areas (short-term damage) and outside fibrotic septa (long-term damage). In vitro studies showed fibrinogen de novo synthesis restricted to hepatocytes.

CONCLUSIONS

The results show fibrinogen/fibrin deposition during short-term liver injury and liver fibrogenesis, which may suggest the involvement of a "clotting-like process" in short-term liver damage and liver fibrosis. The data might indicate that fibrin/fibronectin constitute a "provisional matrix," which affects the attraction and proliferation of inflammatory and matrix-producing cells.

Recipient-derived T cells participate in autoimmune-like hepatic lesions induced by graft-versus-host reaction

Autoimmune-like hepatic lesions were induced by injection of CD4+ T cells from B10.Thy-1.1 mice into MHC class II-disparate (B10.Thy-1.1 x bm12)F1 mice. Hepatic lesions characterized by mononuclear cell accumulation in the portal area of the central vein and around interlobular bile ducts were observed in these recipients. The morphologic features of the lesions resembled primary biliary cirrhosis. The origin of T cells invading at the site of the hepatic lesions was immunohistochemically analyzed. It was shown that many recipient-derived T cells were present at the lesions and that some of them infiltrated the bile duct epithelia. Furthermore, the lesions were weakened when recipient-type T cells were depleted by thymectomy and the administration of anti-Thy-1.2 monoclonal antibody. Recipient-derived T cells were observed to take part in the formation of autoimmune hepatic lesions. These findings suggest the possibility that the tolerance of self-reactive T cells is abrogated by the graft-versus-host reaction.

C1 esterase inhibitor gene expression in rat Kupffer cells, peritoneal macrophages and blood monocytes: modulation by interferon gamma

Kupffer cells (KC) represent the main part of the tissue macrophages. Beside phagocytosis of particulate material, involvement of KC in immunological and inflammatory reactions has been supposed. As C1 esterase inhibitor (C1-INH) is a serine protease inhibitor involved in such processes, the aim of this work was to study C1-INH synthesis in KC and, by comparison, in peritoneal macrophages (PM) and blood monocytes (MC) of the rat. C1-INH synthesis was studied on the protein level by biosynthetic labeling, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and on the RNA level by Northern blotting of total RNA or by in situ hybridization. KC were found to express C1-INH gene spontaneously. C1-INH synthesis represents 1.3 +/- 0.2% of total protein synthesis at day 1 of culture and the absolute amount each cell synthesis remains constant during the whole time in culture. Transcripts of C1-INH were detected both in freshly isolated and in cultured KC. In contrast, spontaneous C1-INH gene expression was not detectable in freshly isolated PM, but only in cultured PM. In MC, C1-INH was not detectable at any time, whatever. Treatment of the cells with interferon gamma increased C1-INH synthesis in KC and in PM and caused an induction of C1-INH synthesis in MC. The results suggest that constitutive C1-INH synthesis is a functional marker for mature tissue macrophages.

Functional heterogeneity of rat liver macrophages: interleukin-1 secretion and Ia antigen expression in contrast with phagocytic activity

To clarify whether immunological heterogeneity exists among liver macrophages and whether this possible heterogeneity corresponds to varying degrees of phagocytic activity, we fractionated liver macrophages according to size via centrifugal elutriation and studied their ability to ingest latex beads, to express Ia antigen and to secrete interleukin-1 (IL-1) in vitro. Larger liver macrophages were found to be more active in ingesting latex beads than smaller ones (p less than 0.01), while smaller liver macrophages were more active in Ia antigen expression and evidenced greater fluorescence at cytofluorometric examination. In addition, smaller liver macrophages elaborated more IL-1 than the larger liver macrophages (p less than 0.05). These results indicate that liver macrophage heterogeneity is seen in at least two important macrophage functions: phagocytosis of large molecules, which provides an important scavenger function, and Ia antigen expression and IL-1 secretion, important components of the immune response.

Tenascin gene expression in rat liver and in rat liver cells. In vivo and in vitro studies

Tenascin is a major glycoprotein constituent of the extracellular matrix with a strong affinity to fibronectin; its distribution is believed to be temporarily and spatially limited. Tenascin gene expression is increased during wound healing processes. As repair mechanisms in chronic liver diseases resemble wound healing we studied tenascin gene expression in rat liver and in isolated rat liver cells. In normal rat liver a tenascin specific antiserum stains sinusoidal cells with fiber-like prolongations, which at the same time are desmin-positive (ITO-cells). In the CCl4-acutely-damaged liver a strong tenascin staining is detected in cells located among the mononuclear cells of the inflammatory infiltrates in the areas of necrosis and in cells of the sinusoids. In CCl4-chronically-damaged liver a strong tenascin staining is demonstrable in the connective tissue septa. In both cases, many of the tenascin-positive cells can be identified as desmin-positive by means of the double-staining fluorescence technique. The wall of larger vessels is always tensacin-negative. The staining pattern obtained with a fibronectin-specific antiserum is somewhat comparable with that of tenascin but the vessel wall was positive. hepatocytes, Kupffer cells, ITO-cells and endothelial cells were isolated from rat liver and studied for their capacity to express the tenascin gene. Biosynthetically labeled tenascin was immunoprecipated from supernatants and cell lysates obtained from cultured ITO-cells and to a much lesser extent from intracellular lysates obtained from endothelial cells; its synthesis in ITO-cells increased during the time in culture. Tenascin was also identified immuno-cytochemically in increasing amount in ITO-cells in culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemical observations on macrophage populations in normal fetal and adult human liver

Phenotypic expression of macrophages was studied immunocytochemically in 25 human fetal livers at various stages of development and in 20 normal human adult livers. A panel of commercially available polyclonal and monoclonal antibodies (KP1, Mac387, LN3, CR3/43, and antibodies against muramidase, alpha-1-antitrypsin, and factor XIIIa) was applied to paraffin sections. From the seventh week of gestation macrophages in the fetal liver showed differences in distribution with the various antibodies. Macrophages in adult liver similarly varied in morphology and phenotypic expression. In the light of these results, we conclude that the population of human liver macrophages is heterogeneous from an early stage of fetal development and that this heterogeneity extends into adult life.

Expression of the gene of the alpha-smooth muscle-actin isoform in rat liver and in rat fat-storing (ITO) cells

Fat storing cells (FSCs) in the liver represent the main site of vitamin A deposition in the body. These cells are considered to play an important role during scar formation and fibrogenesis in the liver. The putative descent of FSCs from the fibroblastic or from the myofibroblastic system have not been determined yet by morphological or immunohistochemical studies. To further define the origin of these liver cells, we analysed the pattern of expression of three structural proteins: vimentin, desmin and the alpha-smooth muscle (SM)-actin isoform in FSCs of the rat liver, in smooth muscle cells (SMCs) from the aorta and in rat skin fibroblasts. FSCs were studied by immunohistochemical methods immediately after isolation, at days 3 and 7 after plating. FSC-gene-expression was also analysed by Northern blot analysis of total RNA extracted from cells in culture at days 3 and 7 after isolation. Arterial SMCs and skin fibroblasts were studied in a similar way. For comparison, isolated rat hepatocytes and Küpffer cells (Kc) were studied. Of freshly isolated FSCs, 100% were vimentin-positive, 50% were desmin-positive, but all were alpha-SM-actin negative. Three days after isolation, FSCs were clearly positive for vimentin and desmin and weakly alpha-SM-actin-positive, as demonstrated by indirect immunofluorescence as well as by the immunoperoxidase technique. Desmin, alpha-SM-actin and vimentin staining was further increased at day 7 after isolation, and alpha-actin specific transcripts in FSC-RNA were clearly detectable at day 7 after isolation. Passaged arterial SMCs were vimentin- and alpha-SM-actin-positive, but desmin-negative and fibroblasts were only vimentin-positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocytes from hepatic inflammatory infiltrate kill rat hepatocytes in primary culture. Comparison with peripheral blood lymphocytes

In the last few years it has become possible in the liver to isolate lymphocytes from inflammatory infiltrates and to culture them in vitro. Most of the lymphocyte clones obtained are CD 8+ cytotoxic cells, but interactions between these lymphocytes and hepatocytes in primary culture have not been analysed previously. In this study, cloned human T lymphocytes from liver biopsies and from the peripheral blood of patients with chronic hepatitis B or primary biliary cirrhosis, after phenotypical and functional characterization into CD 8+ or CD 4+ cytotoxic lymphocytes, were activated in an antigen-independent fashion by adding either anti CD 3 or anti CD 2/R-3 monoclonal antibodies to the cell suspension. The activated cells were then coincubated with rat hepatocytes in primary culture. The killing capacity of the activated lymphocytes was monitored by light and electron microscopy and by measurement of lactic dehydrogenase (LDH)-release into the culture medium. It was found that cytotoxic CD 8+, but not CD 4+ helper lymphocytes very effectively killed hepatocytes. The killing effect was dependent on the time of cocultivation and on effector-target (E/T) ratio. Total breakdown of the hepatocyte monolayer was achieved after 10-20 h coculture and at an E/T ratio of 10 to 1. As LDH-release in the culture medium reached about 80% of the total LDH-content, most of the hepatocytes were lysed by activated lymphocytes. Cytotoxic activity of clones obtained from different biopsies was comparable with that of clones from peripheral blood. Hepatocytes in primary culture seem to be very sensitive to the killing capacity of activated cytotoxic lymphocytes.

Fine structure and function of Kupffer cells

Kupffer cells are macrophages that are attached to the luminal surface or inserted in the endothelial lining of hepatic sinusoids. In this site, Kupffer cells play a key role in host defense by removing foreign, toxic and infective substances from the portal blood and by releasing beneficial mediators. Under some conditions, toxic and vasoactive substances also are released from Kupffer cells which are thought to play a role in a variety of liver diseases. Many of these activities may be modulated by the levels of gut derived endotoxin normally present in the portal blood. The ultrastructural aspects of Kupffer cell structure function in situ are best studied using perfused-fixed livers. In fixed livers, transmission and scanning electron microscopy reveal Kupffer cells during health to be irregular in shape with their exposed surfaces presenting numerous microvilli, filopodia, and lamellopodia. Long filopodia penetrate endothelial fenestrae to secure Kupffer cells to the sinusoid lining. Specific membrane invaginations known as worm-like bodies or vermiform processes are seen in the cytoplasm of Kupffer cells as are numerous endocytotic vesicles and lysosomes which vary in density, shape and size. Sometimes, annulate lamellae connected to the rough endoplasmic reticulum also are found. The principal endocytic mechanisms of Kupffer cells are phagocytosis of particulates and cells, and bristle-coated micropinocytosis for fluid-phase endocytosis of smaller substances. Many of these events are mediated by specific receptors. In some species, Kupffer cells can be distinguished from other sinusoidal lining cells and monocytes by specific cytoplasmic staining or monoclonal antibodies. Kupffer cells have been shown to be of monocytic origin as well as having the capacity for self-replication.

Murine tissue macrophages synthesize and secrete amyloid proteins different to amyloid A (AA)

We recently demonstrated that serum amyloid A (SAA) gene expression can be induced in extrahepatic sites with exception of the brain. Furthermore we demonstrated that tissue macrophages express SAA-gene constitutively and that SAA-gene expression can be increased by endotoxin. Until now the protein corresponding to the SAA-specific mRNA contained in macrophages has not been identified. We compared proteins precipitated from endogenously labelled samples by three antisera against amyloid A (AA) raised in different laboratories. Radiolabelled samples were derived from murine hepatocyte cultures, from cell-free translation of acute phase liver RNA or hepatocytes RNA and from peritoneal macrophages as well as Kupffer cells. All three antisera recognize a protein of 12.5 kDa Mr produced by hepatocytes (SAA), and a major protein of 14.3 kDa Mr contained in the cell-free translation products; this is the precursor of the mature SAA as demonstrated by cleavage experiments with canine pancreas microsomal enzymes. The antisera also recognize two proteins--a major one of 14.5 kDa Mr and a second of 12.5 kDa Mr contained in the supernatants and cell lysates of liver and peritoneal macrophages. New antisera raised against the two proteins do not recognize any protein, either of hepatocyte or of cell-free translation samples; they specifically precipitate two proteins from macrophage samples with the same molecular mass as that of the proteins precipitated by the anti SAA antisera. Murine acute phase sera do not react with the new antisera. However, amyloid deposits of amyloidotic mice specifically react with the new antisera. We describe two new components of murine amyloid produced by tissue macrophages.

Guinea pig Kupffer cells can be activated in vitro to an enhanced superoxide response. I. Comparison with peritoneal macrophages

Guinea pig Kupffer cells were obtained by partial digestion of the liver with pronase and collagenase and purified by centrifugal elutriation. Cells were kept in monolayer culture and their capacity to secrete superoxide anion in response to phagocytosis of zymosan was determined by the cytochrome c method. Compared to resident peritoneal macrophages, Kupffer cells produced somewhat less superoxide (60% +/- 30%). Both cell types were activated by 24 h preincubation with lipopolysaccharide from Salmonella minnesota or muramyl dipeptide to give twice as high a superoxide response to zymosan. The same effect was achieved when Kupffer cells in vitro were incubated for 3 days with supernatants from phytohaemagglutinin-activated peripheral T lymphocytes or recombinant gamma-interferon. These data demonstrate that the resident macrophages of the liver, the Kupffer cells, are able to increase their capacity to secrete reactive oxygen intermediates after proper activation; this fact is possibly important in the pathogenesis of hepatocyte damage upon inflammatory reactions in the liver.

A new monoclonal antibody, UFT-4, reacting with rat Kupffer cells. Immunohistochemical and immunoelectron microscopical analysis with reestimation of the reticuloendothelial system

A new monoclonal antibody, designated UFT-4, reacting with rat Kupffer cells, was produced using sinusoidal liver-cell fraction as an immunogen. Immunohistochemically, UFT-4 reacted with Kupffer cells, interdigitating cells (IDCs), sinus endothelial cells of the spleen, a proportion of reticulum cells, smooth muscle fibers, choroid plexus epithelia and some macrophages. Immunoelectron microscopy disclosed two types of intracytoplasmic positivity: a striated type and a diffuse type. Both appeared to depend on variations in the quantity and distribution of the same antigen. On the other hand, UFT-4 gave a negative result for blood monocytes and most macrophages in lymphatic sinuses, lymphoid follicles, splenic red pulp and loose connective tissue. Cells positive for UFT-4 were mostly considered to belong to a narrow spectrum of the classical reticuloendothelial system, explaining the close relationship existing between some endothelia and some macrophages or reticulum cells. SDS-PAGE analysis of immunoprecipitates showed that the antigen reacting with UFT-4 was of molecule of 36-42 kDa under reducing conditions in the presence of 2-mercaptoethanol. The present results suggest that UFT-4 will be very useful for the study of Kupffer cells and for reconsidering their origin and destination.

The concept of the "perisinusoidal functional unit" of the liver--importance to pathological processes

Non-hepatocytes account for 30 per cent of cells in the liver, with sinusoid-coating endothelial and Kupffer cells being the most common types. In addition, there are some scattered pit cells in the wall. Ito cells (perisinusoidal cells, lipocytes) are located in the Disse space. In this paper a review is given of structural and functional changes of cells in response to pathological conditions with reference to the importance of such changes due to diseases of the liver and the organism in large. Cooperation and interaction among non-hepatocytes, the vascular pole of hepatocytes, and Disse space as the site of reaction are summarised under the concept of the "Perisinusoidal Functional Unit", and the concept is explained in greater detail by examples (lipoprotein catabolism, processes of phagocytosis, vitamin A storage, virus infections, accumulation of pathological substances, fibrosis, and capillarization).

Biosynthesis of the subcomponents C1q, C1r and C1s of the first component of complement (C1) by guinea pig hepatocyte primary cultures

Thus far, the synthesis of C1q by liver cells has not been demonstrated. To investigate this possibility, viable hepatocytes were isolated from the liver of guinea pigs and primary cultures were established. The cells (10(6) cells/ml) were cultured under serum-free conditions for 8 days and the culture medium was changed every 24 h. The few contaminating Kupffer cells were lysed by preincubating the cell cultures with a monoclonal (22C4-8) antibody directed against a nonpolymorphic Ia determinant and preabsorbed rabbit serum. The hemolytic activity of C1 and its subcomponents C1q and C1r/C1s was tested in the supernatants. Guinea pig hepatocyte primary cultures synthesize and secrete up to 3 X 10(3) effective C1q molecules/cell/24 h and 34 X 10(3) effective C1r/C1s molecules/cell/24 h. The synthesis of C1q and C1r/C1s could be reversibly inhibited by cycloheximide (50 micrograms/ml). Furthermore, to demonstrate de novo synthesis of the C1q subcomponent, endogeneous labeling with 3H-proline (or 14C-proline) was performed. The immunoprecipitated C1q from cellular lysates and culture medium was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Compared to biosynthetically labeled guinea pig C1q from peritoneal macrophages, three corresponding bands (30, 28 and 24 kDa, respectively) were detectable in the fluorograph. The data show that guinea pig hepatocytes are able to synthesize C1 subcomponents, whereby the synthesis of C1q and C1r/C1s occurs independently.