Consistent infiltration of thymus-derived T cells into the parenchymal space of the liver in normal mice

After Experimental Trypanosoma cruzi Infection, Dying Hepatic CD3+TCRαβ+B220+ T Lymphocytes Are Rescued from Death by Peripheral T Cells and Become Activated

The unusual phenotype of CD3⁺ T lymphocyte expressing B220, a marker originally attributed to B lymphocytes, was first observed in the liver of Fas/Fas-L-deficient mice as a marker of apoptotic T lymphocytes. However, other CD3⁺B220⁺ T lymphocyte populations were later described in the periphery as functional cytotoxic or regulatory cells, for example. Then, in this work, we studied whether hepatic CD3⁺B220⁺ T lymphocytes could play a role in experimental Trypanosoma cruzi infection. In control and infected mice, we observed two subpopulations that could be discerned based on CD117 expression, which were conventional apoptotic CD3⁺B220⁺(CD117^-) and thymus-independent CD3⁺B220⁺CD117⁺ T lymphocytes. Regardless of CD117 expression, most B220⁺ T lymphocytes were 7AAD⁺, confirming this molecule as a marker of dying T cells. However, after infection, we found that around 15% of the CD3⁺B220⁺CD117⁺ hepatic population became B220 and 7AAD negative, turned into CD90.2⁺, and upregulated the expression of CD44, CD49d, and CD11a, a phenotype consistent with activated T lymphocytes. Moreover, we observed that the hepatic CD3⁺B220⁺CD117⁺ population was rescued from death by previously activated peripheral T lymphocytes. Our results extend the comprehension of the hepatic CD3⁺B220⁺ T lymphocyte subpopulations and illustrate the complex interactions that occur in the liver.

Role of NK, NKT cells and macrophages in liver transplantation

Liver transplantation has become the treatment of choice for acute or chronic liver disease. Because the liver acts as an innate immunity-dominant organ, there are immunological differences between the liver and other organs. The specific features of hepatic natural killer (NK), NKT and Kupffer cells and their role in the mechanism of liver transplant rejection, tolerance and hepatic ischemia-reperfusion injury are discussed in this review.

The adult livers of immunodeficient mice support human hematopoiesis: evidence for a hepatic mast cell population that develops early in human ontogeny

The liver plays a vital role in hematopoiesis during mammalian prenatal development but its hematopoietic output declines during the perinatal period. Nonetheless, hepatic hematopoiesis is believed to persist into adulthood. We sought to model human adult-liver hematopoiesis by transplantation of fetal and neonatal hematopoietic stem cells (HSCs) into adult immunodeficient mice. Livers were found to be engrafted with human cells consisting primarily of monocytes and B-cells with lesser contributions by erythrocytes, T-cells, NK-cells and mast-cells. A resident population of CD117(++)CD203c(+) mast cells was also documented in human midgestation liver, indicating that these cells comprise part of the liver's resident immune cell repertoire throughout human ontogeny. The murine liver was shown to support human multilineage hematopoiesis up to 321 days after transplant. Evidence of murine hepatic hematopoiesis was also found in common mouse strains as old as 2 years. Human HSC engraftment of the murine liver was demonstrated by detection of high proliferative-potential colony-forming cells in clonal cultures, observation of CD38-CD34(++) and CD133(+)CD34(++) cells by flow cytometry, and hematopoietic reconstitution of secondary transplant recipients of chimeric liver cells. Additionally, chimeric mice with both hematopoietic and endothelial reconstitution were generated by intrasplenic injection of immunodeficient mice with liver specific expression of the urokinase-type plasminogen activator (uPA) transgene. In conclusion, the murine liver is shown to be a hematopoietic organ throughout adult life that can also support human hematopoiesis in severely immunodeficient strains. Further humanization of the murine liver can be achieved in mice harboring an uPA transgene, which support engraftment of non-hematopoietic cells types. Thus, offering a model system to study the interaction of diverse human liver cell types that regulate hematopoiesis and immune function in the liver.

Lymphocyte numbers and subsets in the human blood. Do they mirror the situation in all organs?

Lymphocyte numbers in the blood are used to evaluate the immune status on a daily basis in medicine. Several studies have documented the normal ranges of lymphocytes and lymphocyte subsets in the peripheral blood. A variety of techniques and criteria have revealed clear differences between the lymphocyte subsets in childhood and adolescence. Race and gender are also variables for blood lymphocytes, and even environmental factors seem to influence the numbers of some lymphocyte populations. However, do all these variations in lymphocyte subsets in the peripheral blood mirror changes in the lymphocyte populations of the whole body, or is it just a result of different migratory habits of cells? The factors influencing the distribution of lymphocytes in the peripheral blood with regard to the different abilities of T and B cells to migrate to distinct lymphoid or non-lymphoid tissue are summarized. In addition it will be described how the removal of organs (e.g. thymus, spleen, liver) influences the distribution of lymphocytes in the blood. All these parameters should be considered not only in the clinical situation when the immune status of a patient is extrapolated from the lymphocyte numbers in the blood, but also when interpreting treatment effects in patients.

NOD.c3c4 congenic mice develop autoimmune biliary disease that serologically and pathogenetically models human primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease with a strong genetic component characterized by biliary ductular inflammation with eventual liver cirrhosis. The serologic hallmark of PBC is antimitochondrial antibodies that react with the pyruvate dehydrogenase complex, targeting the inner lipoyl domain of the E2 subunit (anti–PDC-E2). Herein we demonstrate that NOD.c3c4 mice congenically derived from the nonobese diabetic strain develop an autoimmune biliary disease (ABD) that models human PBC. NOD.c3c4 (at 9–10 wk, before significant biliary pathology) develop antibodies to PDC-E2 that are specific for the inner lipoyl domain. Affected areas of biliary epithelium are infiltrated with CD3⁺, CD4⁺, and CD8⁺ T cells, and treatment of NOD.c3c4 mice with monoclonal antibody to CD3 protects from ABD. Furthermore, NOD.c3c4-scid mice develop disease after adoptive transfer of splenocytes or CD4⁺ T cells, demonstrating a central role for T cells in pathogenesis. Histological analysis reveals destructive cholangitis, granuloma formation, and eosinophilic infiltration as seen in PBC, although, unlike PBC, the extrahepatic biliary ducts are also affected. Using a congenic mapping approach, we define the first ABD (Abd) locus, Abd1. These results identify the NOD.c3c4 mouse as the first spontaneous mouse model of PBC.

Management of Major Portosystemic Shunting in Small-for-Size Adult Living-Related Donor Liver Transplantation with a Left-Sided Graft Liver

PURPOSE

We investigated the mechanisms of small-for-size graft syndrome by time-lag ligation, a novel approach to treating major portosystemic shunts in small-for-size adult living-related donor liver transplantation (LRDLT) using left-sided graft liver.

METHODS

Five patients with end-stage liver failure and major splenorenal shunting underwent LRDLT using left lobe grafts. The average graft volume to recipient body weight (GV/RBW) ratio was 0.68 +/- 0.14. Two patients underwent time-lag ligation of their splenorenal (SR) shunts on postoperative days (PODs) 8 and 14, respectively. The shunts of the other three patients were untreated.

RESULTS

The portal pressures in the first patient who underwent time-lag ligation rose above 300 mmH(2)O and remained there for 2 weeks. Thus, we ligated the SR shunt in the second patient on POD 14, resulting in an increase from 177 mmH(2)O to 258 mmH(2)O, but it decreased again thereafter. In the other three patients, the SR shunt was not ligated because portal blood flow volumes remained sufficient. Total bilirubin levels in the first time-lag ligation patient rose to 16 mg/dl, paralleling the rise in portal pressures. Although they increased after ligation in the second patient, they did not exceed 10 mg/dl.

CONCLUSIONS

We recommend time-lag ligation if portal venous blood flow decreases in the early post-transplant period, but not until at least 2 weeks after transplantation. If the portal venous blood flow does not decrease, early postoperative ligation is unnecessary. If there are no major portosystemic shunts, making a portosystemic shunt might decompress excessive portal hypertension. With donor safety priority in LRDLT, novel approaches must be developed to enable the use of smaller donor grafts. We describe a potential means of using left lobe grafts in adult LRDLT.

Association of NKT cells and granulocytes with liver injury after reperfusion of the portal vein

Reperfusion of the liver was conducted by clamping the portal vein for 30 min in mice, followed by unclamping. Unique variation in the number of lymphocytes was induced and liver injury occurred thereafter. The major expander cells in the liver were estimated to be natural killer T cells (i.e., NKT cells), whereas conventional T cells and NK cells increased only slightly or somewhat decreased in number and proportion at that time. Reflecting the expansion of NKT cells in the liver, a Th0-type of cytokine profile was detected in sera, and cytotoxic activity was enhanced in liver lymphocytes. In NKT cell-deficient mice including CD1d (-/-) mice and athymic nude mice, the magnitude of liver injury decreased up to 50% of that of control mice. It was also suspected that accumulating granulocytes which produce superoxides might be associated with liver injury after reperfusion. This might be due to stress-associated production of catecholamines. It is known that granulocytes bear surface adrenergic receptors and that they are activated by sympathetic nerve stimulation after stress. The present results therefore suggest that liver injury after reperfusion may be mainly caused by the activation of NKT cells and granulocytes, possibly by their cytotoxicity and superoxide production, respectively.

Liver immunobiology

Tle liver has a number of important functions in innate and adaptive immunity. Contributions to the innate (nonspecific) immune system include production of acute phase proteins, nonspecific phagocytosis of particles, nonspecific pinocytosis of molecules, and nonspecific cell killing. Hepatic involvement in innate immunity contributes to the systemic response to local inflammation, clearance of particles and soluble molecules from the circulation, and killing of invading cells such as neoplastic cells. Liver involvement in the adaptive (specific) immune system includes deletion of activated T cells, induction of tolerance to ingested and self-antigens, extrathymic proliferation of T cells, and deletion of many of the signaling and effector molecules. Hepatic involvement in adaptive immunity allows clearance of activated T cells and signaling molecules following inflammatory reactions, and promotes immunologic tolerance toward potentially antigenic proteins that are absorbed from the intestinal tract. The liver is a major site of extrathymic T cell development, which assumes increasing significance with aging in mammals. Perturbations in hepatic structure or function can result in significant ramifications in both the innate and adaptive immune systems.

Adoptive transfer of NK 1.1+ lymphocytes in immune-mediated colitis: a pro-inflammatory or a tolerizing subgroup of cells?

T lymphocytes expressing NK1.1 marker (NKT) have been suggested to play crucial roles in immune modulation.

AIM

To determine the role of NK1.1+ cells in induction and maintenance of pro-inflammatory and/or tolerizing responses.

METHODS

Colitis was induced in C57/B6 donor mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Donor mice received five oral doses of colonic proteins extracted from TNBS-colitis colonic wall. Depletion of NK1.1+ lymphocytes was performed before lymphocyte harvesting. Splenocytes were harvested and separated into T-cell subpopulations, and transplanted into recipient mice before intracolonic instillation of TNBS. Standard clinical, macroscopic, and microscopic scores, and intracellular staining, flow cytometry, and cytotoxicity assays were performed.

RESULTS

The adoptive transfer of CD4+ and NK1.1+ cells harvested from tolerized mice markedly ameliorated the colitis in recipient mice. In contrast, the adoptive transfer of CD8+ and double negative lymphocytes failed to transfer the tolerance. Recipients of splenocytes from tolerized mice exhibited an increase in CD4+ IL4+/CD4+ IFNgamma+ ratio. In contrast, recipients of splenocytes from NK1.1-depleted-tolerized mice exhibited severe colitis with a significant decrease of the CD4+ IL4+/CD4+ IFNgamma+ ratio. However adoptive transfer of splenocytes from non-tolerized NKT-depleted mice led to an alleviation of colitis with a relative increase of the CD4+ IL4+/CD4+ IFNgamma+ ratio.

CONCLUSIONS

NK1.1+ lymphocytes play a critical role in immune regulation. They may be accountable for an alteration of the inflammatory response and the CD4+ IL4+/CD4+ IFNgamma ratio immune-mediated colitis and in peripheral tolerance induction.

CrmA gene expression protects mice against concanavalin-A-induced hepatitis by inhibiting IL-18 secretion and hepatocyte apoptosis

Activated cytotoxic T-cell-mediated hepatocyte apoptosis via Fas/Fas-ligand and perforin/granzyme pathways are believed to involve the model of concanavalin A (ConA)-induced hepatitis. The purpose of the present study is to investigate whether the cytokine response modifier A (crmA) gene effectively inhibits the hepatocyte apoptosis of ConA-induced hepatitis. We examined survival rates, liver pathology, immune histological changes, and cytokine profiles from mice receiving the recombinant adenovirus vectors containing cre and/or crmA genes, transferred to the liver 3 days before ConA injection, and a crmA gene nonexpression control group. Injection of ConA into mice rapidly led to massive hepatocyte apoptosis, and infiltration of leukocytes, especially CD11b(+) inflammatory cells. In contrast, liver damage was dramatically reduced in the mice that expressed the crmA gene. However, infiltration by CD4(+) cells was not affected. The survival of the mice increased significantly to 100% in the treated group versus the control group. Furthermore, we demonstrated that interleukin (IL)-18 plays an important role in ConA-induced hepatitis, and that crmA expression significantly inhibited IL-18 secretion. Our results showed that the crmA gene effectively inhibits apoptosis induced by ConA hepatitis. This indicates a potential therapeutic usage of crmA for protection from cellular damage due to hepatitis.

Entamoeba histolytica: immunohistochemical study of hepatic amoebiasis in mouse. Neutrophils and nitric oxide as possible factors of resistance

Studies in mice have not rendered conclusive data on cell and humoral factors to support the resistance of this rodent to Entamoeba histolytica infection. In Balb/c and C3H/HeJ mice inoculated with live or fixed trophozoites, we studied the evolution of the hepatic lesion, the kinetics of inflammatory cells, and the participation of some humoral factors in the development of the hepatic amoebic lesion. From the first hour, amoebae were surrounded by neutrophils containing inducible nitric oxide synthase (iNOS); macrophages also expressing iNOS appeared lately, whereas NK cells were not part of the inflammatory infiltrates. On the fourth day, neutrophils, macrophages, T and B lymphocytes, plasma cells, and some NK cells limited the lesions and anti-amoeba antibodies appeared when most parasites had been eliminated. Therefore, the resistance of the mice to E. histolytica probably lies in non-specific immune responses, among which the activation of neutrophils and the production of nitric oxide (NO) may be important amoebicide factors.

Differentiation-dependent and subset-specific recruitment of T-helper cells into murine liver

It has been suggested that the liver traps and deletes activated and potentially harmful T cells, especially of the CD8(+) subset, providing mechanisms to limit systemic immune responses. It is unknown whether this also applies to CD4(+) T cells. In this study, we show that activated stages of CD4(+) T cells were trapped in the liver on intraportal injection. Intravital microscopy showed an immediate adhesion of activated CD4(+) T cells within periportal sinusoids after intraportal injection. Furthermore, we detected high frequencies of interferon gamma (IFN-gamma)-- (Th1) and interleukin 4 (IL-4)-- (Th2) synthesizing effector cells in the liver. Transfer experiments were performed to identify those phenotypes showing specific retention in the liver. Our data show that effector stages and activated cells in general are more efficiently recruited into the liver than resting CD4(+) T cells, similar to what has previously been shown for CD45RB(low) memory cells. In addition, we observed a certain preference for Th1-polarized cells to be trapped by the liver. However, the actual cytokine-producing cells did not specifically enrich among the total population. In conclusion, these data indicate that the liver acts as a filter for activated and memory/effector cells. Cells trapped in the liver might subsequently undergo modulatory influences exerted by the postulated specific microenvironment of the liver.

Having it all? Stem cells, haematopoiesis and lymphopoiesis in adult human liver

Because of its location and function, the liver is continuously exposed to large antigenic loads that include pathogens, toxins and tumour cells, as well as harmless dietary and commensal proteins and peptides. Therefore, the liver must be actively immunocompetent and, at the same time, control inappropriate inflammatory responses to dietary and other harmless antigens encountered in the portal circulation. In addition to conventional CD4+ and CD8+ T lymphocytes from the circulation, several specialized lymphoid populations are found in the liver to meet these diverse immunological challenges. These populations display the functional and phenotypic properties of innate cells as well as conventional CD4+ or CD8+ helper and cytotoxic T lymphocytes and B cells. The innate lymphoid cells include gammadeltaTCR+ T cells, B1-B cells and NKT cells as well as large numbers of NK cells. The origin of these cells is unknown, but their murine counterparts have been shown to be capable of differentiation in situ in adult liver. Because haematopoietic stem cells have been found in adult human liver as well as molecular evidence of T-cell maturation, we hypothesize that some resident human hepatic lymphoid cells, particularly those expressing innate phenotypes, also differentiate locally. In particular, it is likely that the adult human liver is an important site of NK cell maturation. In this review, we explore the evidence for an active lymphopoietic role for the normal adult human liver.

Antigen-specific primary activation of CD8+ T cells within the liver

It is generally accepted that naive T cells recirculate via the blood and lymph, but do not enter nonlymphoid tissues without prior activation and differentiation. In this study, we demonstrate that the liver is an exception to this rule. Naive Des-TCR transgenic CD8(+) T cells specific for H-2K(b) were selectively retained in the liver within a few minutes of adoptive transfer into transgenic Met-K(b) mice expressing H-2K(b) in the liver. Activated CD8(+) cells were found in the liver, but not the blood, as soon as 2 h after transfer and underwent cell division and started to recirculate within 24 h of transfer. In contrast, CD8(+) cells activated in the lymph nodes remained sequestered at that site for 2 days before entering the blood. Our results therefore suggest that, in addition to its previously described role as a non Ag-specific activated T cell graveyard, the liver is involved in Ag-specific activation of naive recirculating CD8(+) T cells. This particular property of the liver, combined with the previously demonstrated ability of hepatocytes to induce tolerance by means of premature CD8(+) T cell death, may be a major mechanism contributing to the acceptance of liver allografts and the chronicity of viral hepatitis.

TNF-alpha-induced expression of adhesion molecules in the liver is under the control of TNFR1--relevance for concanavalin A-induced hepatitis

TNF-alpha has been clearly identified as central mediator of T cell activation-induced acute hepatic injury in mice, e.g., Con A hepatitis. In this model, liver injury depends on both TNFRs, i.e., the 55-kDa TNFR1 as well as the 75-kDa TNFR2. We show in this report that the hepatic TNFRs are not transcriptionally regulated, but are regulated by receptor shedding. TNF directly mediates hepatocellular death by activation of TNFR1 but also induces the expression of inflammatory proteins, such as cytokines and adhesion molecules. Here we provide evidence that resistance of TNFR1(-/-) and TNFR2(-/-) mice against Con A hepatitis is not due to an impaired production of the central mediators TNF and IFN-gamma. Con A injection results in a massive induction of ICAM-1, VCAM-1, and E-selectin in the liver. Lack of either one of both TNFRs did not change adhesion molecule expression in the livers of Con A-treated mice, presumably reflecting the fact that other endothelial cell-activating cytokines up-regulated adhesion molecule expression. However, treatment of TNFR1(-/-) and TNFR2(-/-) mice with murine rTNF revealed a predominant role for TNFR1 for the induction of hepatic adhesion molecule expression. Pretreatment with blocking Abs against E- and P-selectin or of ICAM(-/-) mice with anti-VCAM-1 Abs failed to prevent Con A hepatitis, although accumulation of the critical cell population, i.e., CD4(+) T cells was significantly inhibited. Hence, up-regulation of adhesion molecules during acute hepatitis unlikely contributes to organ injury but rather represents a defense mechanism.