Characteristics of the strongly Ia-positive cells in rat liver

Mini-laparotomy and full laparotomy, but not laparoscopy, alter hepatic macrophage populations in a rat model

BACKGROUND

Immune function is better preserved by laparoscopic versus conventional surgery. Numerous mediators of the systemic trauma response are synthesized and/or regulated by the liver. However, it has been stated that the advantages of laparoscopic surgery are no more obvious when conventional operations are performed via mini-laparotomy. We set out to compare the impact of laparoscopy and mini- and full laparotomy on the hepatic macrophage populations.

METHODS

Male Lewis rats were subjected to anesthesia alone (control), mini-laparotomy (1 cm), full laparotomy (7 cm), or laparoscopy for 60 min. Endpoints were the total protein in the peritoneal lavage fluid, hepatic ED-1 cells (recruited monocytes), hepatic ED-2 cells (Kupffer cells), the expression of OX-6 in the liver, and C-reactive protein (CRP) in plasma.

RESULTS

Protein in the peritoneal lavage fluid increased significantly after all interventions. Full laparotomy was accompanied by an enhancement in ED-1-positive monocytes in the liver parenchyma compared to all other groups (p < 0.001). Mini- and full laparotomy led to an increase in ED-2-positive Kupffer cells (p < 0.001). Laparoscopy did not affect the number of monocytes/macrophages. There was no significant alteration of OX-6 expression in either group. No change in the cellular composition in the periportal fields was observed. The CRP plasma levels did not significantly differ between groups.

CONCLUSIONS

Laparoscopy completely prevents hepatic macrophage populations from expansion and normal cell disposition is preserved. Laparotomy, irrespective of incision size, increases the number of Kupffer cells. Moreover, full laparotomy, but not mini-laparotomy or laparoscopy, causes an increase in hepatic monocyte recruitment. The regulating pathways after surgery differ from other immunologic challenges, such as sepsis, in which immunocompetent cells accumulate and are stimulated in the periportal fields.

Liver nonparenchymal cells involved in hyporesponsiveness induced by portal vein injection of alloantigen

INTRODUCTION

Intrahepatic injection of alloantigen prolongs allograft survival and inhibits T-lymphocyte release of both IL-2 and IFN-gamma but not IL-4. This suggests that intrahepatic processing of antigen lead to a predominance of Th2 cell population with inhibition of Th1 cell type. This study examines the effects of hepatic nonparenchymal cells (NPCs) on T cell function and cytokine mRNA expression profiles.

MATERIALS AND METHODS

Following portal vein (p.v.) injection of allogeneic splenic mononuclear cells (SMNC) in mice, heterotopic cardiac allograft survival and donor-specific immune responses were assessed. The cytokine profiles were evaluated in heart grafts and spleens from transplanted mice, or in recipient lymphocytes stimulated in vitro with alloantigen. The immunoregulatory role of NPCs from p.v. injected mice was evaluated.

RESULTS

Transplanted mice with prolonged graft survival demonstrated increased IL-4, TGF-beta and IL-10 and/or decreased IFN-gamma and IL-2 mRNA expression within the spleen and the transplanted graft. This correlated with increased antigen-specific IL-4, IL-10 and TGF-beta expression in lymphocytes isolated from the p.v. injected mice. In mixed lymphocyte cultures using NPC from p.v. injected mice as regulatory cells, there was decreased proliferation of lymphocytes from the p.v. injected mice in response to allogeneic stimulation, associated with increased IL-4, TGF-beta and IL-10 production and decreased IFN-gamma and IL-2 production. The regulatory effects of the NPC was reversed by prostaglandin E inhibitor.

CONCLUSIONS

Interactions between allogeneic lymphocytes and NPCs results in an impaired Th1 response and preferential shift towards a Th2 cytokine response which may regulate allograft rejection.

Immunologic considerations for therapeutic strategies utilizing allogeneic hepatocytes: hepatocyte-expressed membrane-bound major histocompatibility complex class I antigen sensitizes while soluble antigen suppresses the immune response in rats

Understanding the immunologic effects of hepatocytes is critical because of the potential to use these cells for bioartificial livers, as a vehicle for gene transfer, and as a means to induce donor-specific immunosuppression in organ transplantation. However, this understanding is complicated by the fact that hepatocytes express membrane-bound and soluble forms of major histocompatibility complex (MHC) class I antigen, each with the potential to induce different immune responses. In the present study we first determined the immunologic effect of normal donor-derived hepatocytes in a rat heart transplant model. We then used ex vivo hepatocyte gene transfer to examine the immunologic effects of different forms of hepatocyte-expressed MHC class I antigen. Results showed that intrasplenic injection of purified, donor-strain-specific hepatocytes into recipients primes alloimmunity, as evidenced by acceleration of heart allograft rejection. Interestingly, injection of autologous hepatocytes transfected ex vivo with DNA encoding only membrane-bound donor MHC class I antigen (RT1.A(a)) also accelerated allograft rejection. However, hepatocytes transfected to express only secreted donor MHC antigen prolonged transplant survival. Limiting-dilution analysis of lymphocytes from animals treated with hepatocytes producing only secreted alloantigen showed an antigen-specific reduction in cytotoxic T lymphocyte (CTL) and helper T lymphocyte (HTL) precursors. Further analysis of CTL populations by flow cytometry revealed a relatively high percentage of nonviable cells, implying that soluble antigen promotes allospecific CTL death. In summary, this study suggests that hepatocyte-expressed MHC class I molecules have opposing immunologic effects, with the membrane-bound antigen inducing immunologic sensitization, and the soluble antigen promoting donor-specific immunosuppression.

Immunogenic role of Kupffer cells in a rat model of acute liver allograft rejection

Kupffer cells (KCs) are of bone-marrow origin. After liver transplantation, recipient KCs are supposed to replace donor KCs. On the other hand, KCs are currently hypothesized to play a major immunogenic role in acute liver allograft rejection. In the present study, we investigated the immunogenic role of KCs in acute rat liver allograft rejection. For this purpose, we depleted the donor KCs using intravenous injection of liposome-encapsulated dichloromethylene diphosphonate (DMDP) in the fully allogenic ACI-to-LEW rat liver transplantation model. Kupffer cell depletion was confirmed using monoclonal antibodies ED2. In a first set of experiments, graft survival was evaluated, as were body weight and serum bilirubin changes, after the transplantation. Graft survival time showed no difference between the groups (treated, 12.5 +/- 0.92 days; control, 11.9 +/- 0.80 days). Body weight and serum bilirubin changes were similarly affected in both groups. In a second set of experiments, recipients were killed on day 6 after the transplantation, and rejection was histologically graded from 0 to 4. All grafted livers were judged as grade 3 regardless of treatment. ED2 staining showed KCs repopulation in both untreated and the dichloromethylene diphosphonate treated livers. The results of the present study provide evidence that KCs do not play an important immunogenic role in acute liver allograft rejection of the rat.

Schistosome eggs in the portal vein can induce tolerance

Schistosoma japonicum lives in the portal vein and/or mesenteric vein of patients, producing numerous eggs which eventually induce multiple granulomas in the liver and the intestine. The experimental administration of Schistosoma japonicum eggs via the portal vein in the mouse induces tolerance both in the footpad reaction and granuloma formation in the lung. Thus, the presence of Schistosoma japonicum in the portal vein is beneficial to the parasites, not only for receiving enriched nutrition from the blood of the portal vein, but also for inducing immunological tolerance in the hosts. However, prior intravenous injection of gadolinium chloride abolishes such tolerance, indicating the role of Kupffer cells in the induction of tolerance via the portal vein.

A major histocompatibility complex class I-related Fc receptor for IgG on rat hepatocytes

Intestinal epithelial cells of the neonatal rat and mouse have been shown to express a major histocompatibility complex (MHC) class I-like Fc receptor, or FcRn, which transports IgG in an apical to basolateral direction. Previous studies have suggested the possible expression of this receptor beyond the neonatal period within the liver. Since bile contains high levels of IgG, we sought to determine whether the FcRn was functionally expressed by adult rat hepatocytes. Using primers specific for FcRn, which did not cross hybridize with MHC class I transcripts, FcRn DNA was amplified by reverse transcriptase polymerase chain reaction from RNA of adult rat hepatocytes. This RNA contained functional FcRn transcripts as it encoded a beta 2-microglobulin-associated cell surface protein as determined by immunoprecipitation of biotinylated cell surface proteins with a polyclonal anti-FcRn specific antiserum. Western blotting of hepatocyte canalicular (apical) and sinusoidal (basolateral) plasma membranes with an FcRn-specific monoclonal antibody further confirmed the protein expression and suggested that FcRn was enriched on the canalicular surface membranes. FcRn, on the surface of hepatocytes, was biologically functional as it bound Fc fragments of IgG at pH 6.0 but not 8.0, which is the same pH dependence observed for FcRn in rat neonatal enterocytes. Thus, FcRn is functionally expressed outside of the neonatal period on the canalicular cell surface of adult hepatocytes. This suggests that hepatocyte FcRn may bind luminal IgG, providing a potential functional communication between parenchymal immune cells and bile.

Enhancement of rat hepatic macrophages by treatment with interleukin-2 and streptococcal preparation OK432, with reference to antitumor activity, soluble factor production and Ia expression

The effect of biological response modifiers, such as interleukin-2 (IL-2) and streptococcal preparation OK432, on the functions of hepatic macrophages was investigated. The macrophages, even with no exogenous stimulation, produced superoxide anion (O2-) and tumor necrosis factor (TNF), displayed cytotoxicity against K562 cells and cytostasis against P815 cells and expressed immune-region-associated antigen (Ia). IL-2 administered in vitro or in vivo enhanced O2- production by hepatic macrophages and the intravenous injection of OK432 also enhanced O2 production. Furthermore, IL-2 added to the culture medium of hepatic macrophages isolated from OK432-injected rats augmented O2- production even more. The TNF production and Ia expression of the macrophages were also increased by the intravenous injection of OK432. As with O2- production, the cytotoxicity of the cells was enhanced by OK432 injection or by IL-2 added to the culture medium and the combination of OK432 and IL-2 augmented their cytotoxicity even more. Thus, the present study suggested that IL-2 and OK432 induce the augmentation of the antitumor activity of hepatic macrophages, partly as a result of the increase in production of O2- and TNF and Ia expression.

Scavenger functions of the liver endothelial cell

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Specific antibody synthesis and biliary secretion by the rat liver after intestinal immunization with cholera toxin

This study was designed to investigate the location, specificity, and significance of antibody-containing cells in the liver. After intestinal administration of cholera toxin, high numbers of specific antibody-containing cells appeared in the liver during the early priming period and after boosting. In contrast, a significant number of specific antibody-containing cells appeared in the lamina propria of the intestine only after boosting. In the liver, the specific antibody-containing cells were predominantly located in the sinusoidal region of zone 1 of the liver lobules. About 80% of the specific antibody-producing cells in the liver synthesized anticholera toxin antibody of the immunoglobulin A class. During the priming period, the concentration of immunoglobulin A anticholera toxin in bile paralleled the increase and decrease in the number of specific antibody-containing cells in the liver. Liver perfusion experiments indicated that during the priming period at least 70% of the biliary immunoglobulin A anticholera toxin antibody was synthesized within the liver, whereas 30% was synthesized in the liver after boosting. Thus, during the early immune response, the liver seems to be the major source for specific biliary antibody to intestinally administered cholera toxin.

Evidence for a migratory capability of rat Kupffer cells to portal tracts and hepatic lymph nodes

The present study concerns the migratory ability of Kupffer cells in the rat. Phagocytic cells were labeled with colloidal carbon or gold, these markers being administered intravenously either into a tail vein, which resulted in generalized reticuloendothelial uptake, or in low dose into the portal vein, which produced uptake by Kupffer cells alone. Cells containing marker were observed in the portal tracts and in hepatic lymph nodes from 1 to 3 days after injection into the portal vein. The direct movement of single marker particles to the portal tracts could be excluded. Since injection of marker into the portal vein labeled Kupffer cells exclusively, whereas blood cells, splenic and bone marrow macrophages remained unlabeled, the labeled cells in the portal tracts and hepatic lymph nodes appeared to be former Kupffer cells migrating which had migrated to these sites.

The Kupffer cell in experimental extrahepatic cholestasis in the rat--a light microscopy, immunohistochemical and electron microscopy study

Kupffer cell phagocytic function is reduced in the presence of obstructive jaundice. To investigate possible mechanisms we report a study of the rat liver in extrahepatic cholestasis, using light microscopy, immunohistochemistry and electron microscopy, Immunohistochemistry was performed with monoclonal antibodies specific for rat Kupffer cells ED 1, ED 2 and ED 3 and monoclonal antibodies directed against class II antigens of the rat major histocompatibility complex Ox 3 and Ox 6. Extrahepatic cholestasis was produced by bile duct ligation. In bile duct ligated animals light microscopy showed proliferation of bile ductules and an increase in sinusoidal cells. Immunohistochemistry with ED 1, ED 2 and ED 3 demonstrated a marked increase in the number of positive cells, but few of these cells were positive with Ox 3 and Ox 6, whereas the proliferating bile ductules were strongly positive. Electron microscopy revealed two homogeneous granular substances within the sinusoidal lumen and loss of the space of Disse. Despite a reduction in Kupffer cell phagocytic function in obstructive jaundice there is an increase in Kupffer cells, but these cells appear to be in an inactivated state as few express class II antigens on their surface. Furthermore the granular substance within the space of Disse may interfere with function.