Immunosuppression induced by hepatic portal venous immunization spares reactivity in IL-4 producing T lymphocytes

An Eye on Kupffer Cells: Development, Phenotype and the Macrophage Niche

Macrophages are key participants in the maintenance of tissue homeostasis under normal and pathological conditions, and implement a rich diversity of functions. The largest population of resident tissue macrophages is found in the liver. Hepatic macrophages, termed Kupffer cells, are involved in the regulation of multiple liver functionalities. Specific differentiation profiles and functional activities of tissue macrophages have been attributed to the shaping role of the so-called tissue niche microenvironments. The fundamental macrophage niche concept was lately shaken by a flood of new data, leading to a revision and substantial update of the concept, which constitutes the main focus of this review. The macrophage community discusses contemporary evidence on the developmental origins of resident macrophages, notably Kupffer cells and the issues of heterogeneity of the hepatic macrophage populations, as well as the roles of proliferation, cell death and migration processes in the maintenance of macrophage populations of the liver. Special consideration is given to interactions of Kupffer cells with other local cell lineages, including Ito cells, sinusoidal endothelium and hepatocytes, which participate in the maintenance of their phenotypical and functional identity.

The Liver-Immunity Nexus and Cancer Immunotherapy

The impact of liver metastases on immune checkpoint-inhibitor effectiveness in patients with solid-tumor malignancies has been the focus of several recent clinical and translational studies. We review the literature describing the immune functions of the liver and particularly the mechanistic observations in these studies. The initial clinical observation was that pembrolizumab appeared to be much less effective in melanoma and non-small cell lung cancer (NSCLC) patients with liver metastasis. Subsequently other clinical studies have extended and reported similar findings with programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) inhibitors in many cancers. Two recent translational studies in animal models have dissected the mechanism of this systemic immune suppression. In both studies CD11b⁺ suppressive macrophages generated by liver metastasis in a two-site MC38 model appear to delete CD8⁺ T cells in a FasL-dependent manner. In addition, regulatory T-cell (Treg) activation was observed and contributed to the distal immunosuppression. Finally, we discuss some of the interventions reported to address liver immune suppression, such as radiation therapy, combination checkpoint blockade, and Treg depletion.

Systemic delivery of factor IX messenger RNA for protein replacement therapy

Safe and efficient delivery of messenger RNAs for protein replacement therapies offers great promise but remains challenging. In this report, we demonstrate systemic, in vivo, nonviral mRNA delivery through lipid nanoparticles (LNPs) to treat a Factor IX (FIX)-deficient mouse model of hemophilia B. Delivery of human FIX (hFIX) mRNA encapsulated in our LUNAR LNPs results in a rapid pulse of FIX protein (within 4-6 h) that remains stable for up to 4-6 d and is therapeutically effective, like the recombinant human factor IX protein (rhFIX) that is the current standard of care. Extensive cytokine and liver enzyme profiling showed that repeated administration of the mRNA-LUNAR complex does not cause any adverse innate or adaptive immune responses in immune-competent, hemophilic mice. The levels of hFIX protein that were produced also remained consistent during repeated administrations. These results suggest that delivery of long mRNAs is a viable therapeutic alternative for many clotting disorders and for other hepatic diseases where recombinant proteins may be unaffordable or unsuitable.

Portal vein complications after pediatric liver transplantation

Relatively few pediatric donors are available in relation to the number of children waiting for a liver transplant. This limited number of pediatric donor livers leads to the use of adult livers, usually requiring more complex portal vein (PV) anastomoses. These anastomoses are complicated by differences in PV caliber between donors and recipients, as well as by limitations of PV length, which may be inadequate to reach the recipient spleno-mesenteric junction. Three types of post-transplant complications result from these complexities: 1) anomalies of the portal flow; 2) stenosis of the PV anastomosis; and 3) PV thrombosis. Abnormal portal flow may rarely need a specific intervention, but persistent stenosis or appearance of signs of portal hypertension need to be corrected. Balloon dilatation and placement of a stent are usually successful to repair stenosis. Portal vein thromboses are in general diagnosed in the immediate post-operative period and frequently lead to re-transplantation; however, thrombolytic therapy should be attempted in children without major signs of liver necrosis. When intra-hepatic portal vein(s) are permeable, despite extrahepatic PV thrombosis, a Meso-Rex shunt may be the indicated therapy.

Kupffer cells express a unique combination of phenotypic and functional characteristics compared with splenic and peritoneal macrophages

The immunostimulatory role of Kupffer cells in various inflammatory liver diseases is still not fully understood. In this study, phenotypic and functional aspects of Kupffer cells from healthy C57BL/6 mice were analyzed and compared with those of splenic and peritoneal macrophages to generate a blueprint of the cells under steady-state conditions. In the mouse liver, only one population of Kupffer cells was identified as F4/80(high)CD11b(low) cells. We observed that freshy isolated Kupffer cells are endocytic and show a relatively high basal ROS content. Interestingly, despite expression of TLR mRNA on Kupffer cells, ligation of TLR4, TLR7/8, and TLR9 resulted in a weak induction of IL-10, low or undetectable levels of IL-12p40 and TNF, and up-regulation of CD40 on the surface. Kupffer cells and splenic macrophages show functional similarities, in comparison with peritoneal macrophages, as reflected by comparable levels of TLR4, TLR7/8, and TLR9 mRNA and low or undetectable levels of TNF and IL-12p40 produced upon TLR ligation. The unique, functional characteristics of Kupffer cells, demonstrated in this study, suggest that Kupffer cells under steady-state conditions are specialized as phagocytes to clear and degrade particulates and only play a limited immunoregulatory role via the release of soluble mediators.

Hepatic acute phase proteins--regulation by IL-6- and IL-1-type cytokines involving STAT3 and its crosstalk with NF-κB-dependent signaling

The function of the liver as an important constituent of the immune system involved in innate as well as adaptive immunity is warranted by different highly specialized cell populations. As the major source of acute phase proteins, including secreted pathogen recognition receptors (PRRs), short pentraxins, components of the complement system or regulators of iron metabolism, hepatocytes are essential constituents of innate immunity and largely contribute to the control of a systemic inflammatory response. The production of acute phase proteins in hepatocytes is controlled by a variety of different cytokines released during the inflammatory process with IL-1- and IL-6-type cytokines as the leading regulators operating both as a cascade and as a network having additive, inhibitory, or synergistic regulatory effects on acute phase protein expression. Hence, IL-1β substantially modifies IL-6-induced acute phase protein production as it almost completely abrogates production of acute phase proteins such as γ-fibrinogen, α(2)-macroglobulin or α(1)-antichymotrypsin, whereas production of for example hepcidin, C-reactive protein and serum amyloid A is strongly up-regulated. This switch-like regulation of IL-6-induced acute phase protein production by IL-1β is due to a complex processing of the intracellular signaling events activated in response to IL-6 and/or IL-1β, with the crosstalk between STAT3- and NF-κB-mediated signal transduction being of particular importance. Recent data suggest that in this context complex formation between STAT3 and the p65 subunit of NF-κB might be of key importance. The present review summarizes the regulation of acute phase protein production focusing on the role of the crosstalk of STAT3- and NF-κB-driven pathways for transcriptional control of acute phase gene expression.

The liver as a lymphoid organ

The liver receives blood from both the systemic circulation and the intestine, and in distinctive, thin-walled sinusoids this mixture passes over a large macrophage population, termed Kupffer cells. The exposure of liver cells to antigens, and to microbial products derived from the intestinal bacteria, has resulted in a distinctive local immune environment. Innate lymphocytes, including both natural killer cells and natural killer T cells, are unusually abundant in the liver. Multiple populations of nonhematopoietic liver cells, including sinusoidal endothelial cells, stellate cells located in the subendothelial space, and liver parenchymal cells, take on the roles of antigen-presenting cells. These cells present antigen in the context of immunosuppressive cytokines and inhibitory cell surface ligands, and immune responses to liver antigens often result in tolerance. Important human pathogens, including hepatitis C virus and the malaria parasite, exploit the liver's environment, subvert immunity, and establish persistent infection.

Induction of antigen-specific regulatory T cells in the liver-draining celiac lymph node following oral antigen administration

Regulatory T cells are induced by oral administration of an antigen, but the physiological requirements and localization of the inductive sites are largely unknown. Using an adoptive transfer system of cells transgenic for ovalbumin T-cell receptor (OVA TCR tg), we found that antigen-specific CD4+ T cells were activated in the liver-draining celiac lymph node (CLN) shortly after ovalbumin feeding, and that a significantly higher proportion of the T cells in the CLN developed into the putative regulatory phenotype [co-expressing CD25 with the glucocortico-induced tumour necrosis factor (TNF) receptor family related gene (GITR), cytotoxic T-lymphocyte antigen (CTLA)-4 and CD103] than in Peyer's patches, the mesenteric and peripheral lymph nodes and the spleen. In addition, a particularly high level of expression of CD103 on the OVA-specific T cells in the CLN may favour homing to the epithelium of the intestine. While equally suppressive, OVA tg T cells isolated from the CLN of OVA-fed DO11.10 mice were less dependent on transforming growth factor (TGF)-beta for suppression than cells isolated from the peripheral and mesenteric lymph nodes, which indicates the involvement of an additional suppressive mechanism. The expression of FoxP3 was not up-regulated in any of the lymph node compartments studied. Our phenotypic and functional findings suggest that the induction of regulatory T cells in the CLN may be relevant in the control of the immune response to dietary antigens.

Regional oral tolerance in transgenic 2C mice

BACKGROUND

Antigen injected subcutaneously (SQ) results in a strong systemic immune response, whereas antigen infused orally or by the portal vein tends to induce tolerance. Nontransgenic C57BL/6J (H-2(b)), or B6, mice and transgenic 2C mice (that express a cytotoxic T cell receptor against major histocompatibility complex Class I L(d)) were used to investigate the regional and systemic responses to oral antigen.

METHODS

B6 (H-2(b)) and 2C (H-2(b)) mice were given either saline or BALB/cByJ (H-2(d), L(d+)) (BALB/c) spleen cells (SCs) (25 x 10(6)) by oral gavage (PO) on day 0. Injection of 10 x 10(6) BALB/c SCs SQ was performed after 7 days, followed by a footpad injection of 10 x 10(6) BALB/c SC on day 14. Specific footpad swelling was measured 24 hours later by means of a micrometer. Mixed lymphocyte culture was performed on splenic and mesenteric lymph node (MLN) lymphocytes. The percentage of splenic and MLN CD4+ and CD8+ T cells was quantitated by fluorescence activated cell sorter. Cytokine messenger RNA (mRNA) and protein was measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Whereas B6 mice were shown to have specifically decreased responsiveness to Balb/c cells in vivo and in vitro after oral Balb/c, 2C mice did not demonstrate any downregulation in delayed-type hypersensitivity responsiveness or splenic lymphocyte proliferation. However, MLN lymphocytes from 2C mice did demonstrate decreased proliferation against Balb/c after oral Balb/c gavage (P < .01). Subset percentages of naïve B6 (n=8) spleen and MLN lymphocytes were 50% to 52% for CD4+ and 46% to 47% for CD8+ T cells. These percentages were unchanged in B6 mice after PO Balb/c. Subset percentages of naïve 2C (n=6) spleen and MLN lymphocytes were 2% to 5% for CD4+ and 61% to 64% for CD8+ T cells. After PO Balb/c, MLN CD4+ and CD8+ T cells were unchanged, whereas splenic CD8+ T cells decreased to 44% to 48% and CD4+ T cells increased to 32% to 33% (P < .05, P < .05 vs naïve 2C spleen). After PO Balb/c, inflammatory interleukin (IL)-2 and interferon gamma mRNA and protein were increased in 2C spleen cells, whereas they were decreased in 2C MLN. Anti-inflammatory cytokine IL-4 and IL-10 mRNA and protein were increased in 2C MLN after PO Balb/c, whereas they were not detectable in 2C spleen cells.

CONCLUSIONS

Systemic oral tolerance can be induced in B6 mice, whereas only regional mesenteric lymph node tolerance develops in transgenic 2C mice. The inability to induce systemic oral tolerance in 2C mice appears to be due to a significant increase in peripheral (splenic) CD4+ T cells.

Liver sinusoidal endothelial cells are insufficient to activate T cells

Liver sinusoidal endothelial cells (LSEC) have been reported to express MHC class II, CD80, CD86, and CD11c and effectively stimulate naive T cells. Because dendritic cells (DC) are known to possess these characteristics, we sought to directly compare the phenotype and function of murine LSEC and DC. Nonparenchymal cells from C57BL/6 mice were obtained by collagenase digestion of the liver followed by density gradient centrifugation. From the enriched nonparenchymal cell fraction, LSEC (CD45(-)) were then isolated to 99% purity using immunomagnetic beads. Flow cytometric analysis of LSEC demonstrated high expression of CD31, von Willebrand factor, and FcgammaRs. However, unlike DC, LSEC had low or absent expression of MHC class II, CD86, and CD11c. LSEC demonstrated a high capacity for Ag uptake in vitro and in vivo. Although acetylated low-density lipoprotein uptake has been purported to be a specific function of LSEC, we found DC captured acetylated low-density lipoprotein to a similar extent in vivo. Consistent with their phenotype, LSEC were poor stimulators of allogeneic T cells. Furthermore, in the absence of exogenous costimulation, LSEC induced negligible proliferation of CD4(+) or CD8(+) TCR-transgenic T cells. Thus, contrary to previous reports, our data indicate that LSEC alone are insufficient to activate naive T cells.

Oral and portal venous tolerance in the interferon-gamma knockout (GKO) mouse

BACKGROUND

The role of the proinflammatory cytokine interferon-gamma (IFN-gamma) in the development of oral or portal venous tolerance is poorly defined. By using knockout mice for IFN-gamma (GKO mice), we investigated the effect of both oral and portal venous administration of alloantigen on the systemic delayed type hypersensitivity (DTH) response to alloantigen rechallenge.

MATERIALS AND METHODS

C57BL/6 (B6) control and GKO mice (also on a B6 background) were given either saline or BALB/c spleen cells (25 million) by oral gavage (PO) or by injection into the portal vein (PV) on day 0. The injection of 10 million BALB/c spleen cells subcutaneously into the dorsal flanks was performed after 7 days followed by footpad injection of 10 million BALB/c spleen cells on day 14. Specific footpad swelling was measured 24 h later using a micrometer. Splenocyte responsiveness was measured by in vitro mixed lymphocyte culture and cytotoxic T lymphocyte assay. Cytokine production of interleukin (IL)-2, IL-4, IL-10, and IFN-gamma was measured by enzyme-linked immunosorbent assay.

RESULTS

Although B6 mice given PO or PV saline demonstrated a DTH response of 0.47 +/- 0.04 mm and 0.49 +/- 0.05 mm, respectively, in GKO mice, a greater DTH response of 0.72 +/- 0.08 mm and 0.75 +/- 0.05 mm was measured after either PO or PV saline (P < 0.05, P < 0.05, respectively). In vitro MLC and CTL confirmed the heightened DTH response to BALB/c observed in GKO versus B6. Despite this heightened response in control GKO mice, the DTH response was completely suppressed in both GKO and B6 mice, after both PO and PV BALB/c feedings (P < 0.001, P < 0.001, respectively, in both GKO and B6 mice). The unchanged brisk response to third-party C3H/HeJ demonstrated antigenic specificity.

CONCLUSIONS

Although DTH responsiveness to alloantigen is increased in the absence of IFN-gamma, both oral and portal venous alloantigen-specific tolerance can still be established in GKO mice similar to that in control B6 mice. The achievement of a tolerogenic immune response by both oral and portal venous routes indicates that lack of IFN-gamma does not preclude the induction of tolerance in this murine model.

Donor-specific antigen transfusion-mediated skin-graft tolerance results from the peripheral deletion of donor-reactive CD8+ T cells

BACKGROUND

The mechanism of donor-specific transfusion (DST)-induced long-term skin-graft survival is examined in 2CF1 (2C x dm2) transgenic and B6F1 (C57BL/6 x dm2) nontransgenic mice in which CB6F1 (Balb/c x B6) DST and donor skin grafts differ from 2CF1 or B6F1 recipients only at major histocompatibility complex class I Ld.

METHODS

Saline (control) or allogeneic CB6F1 spleen cells were injected intravenously into 2CF1 and B6F1 mice. One week later, CB6F1 tail skin was transplanted onto the dorsum of these mice. Fluorescence-activated cell sorter analysis (flow cytometric analysis) of peripheral blood was performed 2 days before DST, 5 days after DST, and 7, 14, 21, 28, and 75 days after skin grafting. Splenocyte responsiveness was measured by in vitro mixed lymphocyte culture and cytotoxic T lymphocyte. Cytokine protein production (interleukin [IL]-2 and interferon-gamma) was measured by enzyme-linked immunosorbent assay.

RESULTS

Whereas all CB6F1 skin grafts in control saline-treated 2CF1 and B6F1 mice were rejected, 100% of 2CF1 and B6F1 pretreated with CB6F1 DST accepted the class I Ld disparate donor skin indefinitely. DST followed by a CB6F1 skin graft led to a significant deletion of donor-reactive CD8+ T cells by fluorescence-activated cell sorter analysis and decreased production of the inflammatory cytokines IL-2 and interferon-gamma. The hyporesponsiveness of residual CD8+ T cells in mixed lymphocyte culture and cytotoxic T lymphocyte to Ld after DST was restored to normal by IL-2.

CONCLUSION

These findings demonstrate that administration of DST uniformly results in long-term Ld+ skin-allograft acceptance. This tolerance induction is related to both a significant decrease in donor-reactive CD8+ transgenic T cells and anergy of the residual CD8+ T cells.

Mechanism of portal venous tolerant long-term MHC Class I L(d)-specific skin graft survival in transgenic 2CF1 mice

BACKGROUND

Administration of alloantigen via the portal vein (PV) in non-transgenic animals has been shown to promote immunologic tolerance and enhance transplant allograft survival. The underlying mechanisms remain unclear. In 2C x dm2 F1 (2CF1) transgenic mice, the monoclonal antibody, 1B2, identifies specific 2C TCR transgenic CD8+ T cells that are cytotoxic against Class I MHC L(d). In these mice, the specific response by these cells to L(d+) skin grafts after PV administration of L(d+) antigen was determined.

MATERIALS AND METHODS

Saline (control) or allogeneic C57BL/6 x BALB/c F1 (CB6F1) spleen cells (25 x 10(6)), which differ from 2CF1 only at L(d), were injected PV into 2CF1 mice. One week later, CB6F1 tail skin was transplanted onto the dorsum of these 2CF1 mice. Skin graft rejection was defined as >50% loss of the graft. Parallel experiments were performed in non-transgenic littermates [B6F1 (C57BL/6 x dm2)]. FACS analysis of 2CF1 peripheral blood for 1B2+, CD4+, and CD8+ T cells was performed 2 days before PV injection (9 days prior to skin grafting), 5 days after PV injection (2 days prior to skin grafting), and 7, 14, 21, 28, and 60 days after skin grafting. FACS analysis of nai;ve, saline control, and CB6F1 PV-treated 2CF1 thymocytes was also performed. Responsiveness of saline (control)-treated and PV-treated 2CF1 splenocytes was measured by in vitro cytotoxic T lymphocyte (CTL).

RESULTS

All CB6F1 skin grafts were rejected in <14 days by PV saline controls. However, a single PV injection of donor L(d+) CB6F1 cells was sufficient to induce indefinite CB6F1 (L(d+)) skin allograft survival in 100% of non-transgenic B6F1 and transgenic 2CF1 (anti-L(d)) TCR transgenic recipients. FACS analysis of 1B2+ T cells demonstrated that PV injection of donor antigen followed by a CB6F1 skin graft led to a 70% decrease in peripheral donor-reactive 1B2+ CD8+ T cells by day 7, while central thymocytes were unchanged. CTL of 2CF1 splenocytes following PV CB6F1 demonstrated that they were hyporesponsive to L(d) compared to saline-treated 2CF1 splenocytes. Despite recovery of peripheral CD8+ T cells to near normal levels by 60 days post-transplantation, skin graft survival persisted indefinitely.

CONCLUSIONS

Administration of specific PV antigen results in exquisite long-term L(d+) skin allograft acceptance. This tolerance induction is related to a significant peripheral deletion of donor-reactive 1B2+ CD8+ transgenic T cells and anergy of the residual T cells.

CD1-dependent natural killer (NK1.1(+)) T cells are required for oral and portal venous tolerance induction

BACKGROUND

Local antigen presentation via either the oral (PO) or the portal venous (PV) routes results in suppression of systemic delayed-type hypersensitivity (DTH). The responsible cell populations are not well defined. Because NK1.1(+) T cells express the Fas ligand and produce high levels of the immunosuppressive cytokine, IL-4, they may play a role in both activated T-cell apoptosis and a Th1 to Th2 immune shift, thus promoting tolerance induction.

METHODS

C57BL/6 mice were tolerized to BALB/c alloantigen by PV or PO spleen cells (25 x 10(6)) on Day 0. Subcutaneous (SQ) challenge with 10 x 10(6) BALB/c cells on Day 7 was followed by footpad injection of 10 x 10(6) BALB/c cells on Day 14. Footpad swelling was measured 24 h later. A single injection of the NK1.1(+) cell-depleting antibody, PK-136, was given IP (10 mg/kg) 2 days prior to PV or PO antigen. Flow cytometry evaluated NK1.1(+) cell depletion. CD1 knockout (KO) mice, lacking NK1.1(+) T cells, were also challenged with PV and PO Balb/c in parallel experiments.

RESULTS

The DTH to BALB/c antigen was markedly suppressed in C57BL/6 mice when this alloantigen was given by either PO or PV routes (P < 0.001, P < 0.001). The maintenance of an unaltered response to third-party C3H/HeJ demonstrated alloantigenic specificity. Administration of the anti-NK1.1 T cell monoclonal antibody, PK-136, resulted in complete restoration of in vivo DTH responsiveness in PO tolerance (P < 0.01), and partial restoration in PV tolerance (P < 0.05) in C57BL/6 mice. FACS confirmed virtually complete depletion of liver, splenic, Peyer's patch, and mesenteric lymph node NK1.1(+) lymphocytes. Development of both PO and PV tolerance was prevented in CD1 KO mice.

CONCLUSION

NK1.1(+) T cells play an essential role in antigen-specific suppression of the DTH response mediated by both oral and portal venous tolerance.

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.

High-dose peripheral blood stem cell infusion: a strategy to induce donor-specific hyporesponsiveness to allografts in pediatric renal transplant recipients

We designed and implemented a clinical trial to achieve zero-rejection status in pediatric renal allograft recipients, using granulocyte-macrophage colony-stimulating factor (GM-CSF)-stimulated peripheral blood stem cell (PBSC) infusion. We studied 44 consecutive patients: 24 volunteers in a treated group (Tn) and 20 in a control group (Cn). Both groups were comparable with respect to clinical and laboratory parameters. The Tn group had 70.8% one haplo-match donors and the Cn group had 80% one haplo-match donors. Patients in the Tn group received cyclosporin A (CsA) and 0.4 mg/kg body weight prednisolone as immunosuppressants; azathioprine was added for patients of the Cn group, who received 1 mg/kg body weight prednisolone together with CsA. Living-related donors (LRD) of patients in the Tn group received GM-CSF 450 microg on four consecutive days followed by leucopheresis and immediate transfusion of unmodified PBSC into the recipient. This procedure was repeated once/twice, with one portal and one/two systemic infusions. Our aim was to maximize the dose of PBSC. The total average dose was 22 x 10(8) cells/kg body weight. Lymphocyte cross-match (LCM) was performed before GM-CSF injection and after the last PBSC infusion. Follow-up over an 18-month period revealed 100% graft survival with sustained low serum creatinine (SCr) values in patients of the Tn group as compared with 80% graft survival in patients of the control group who had marginally higher SCr levels. Absence of graft vs. host disease (GvHD), acute rejection episodes, and low incidence of cytomegalovirus (CMV) disease were the principal benefits of this protocol.

A new method for tolerance induction: busulfan administration followed by intravenous injection of neuraminidase-treated donor bone marrow

The portal venous (p.v.) administration of foreign cells induces donor-specific tolerance. Recently, we have demonstrated that the p.v. administration of donor cells elicits donor-specific tolerance across major histocompatibility complex barriers. In the present study, utilizing the intrahepatic tolerance-inducing system, we have established a new method for organ transplantation using both busulfan ([Bu] to provide a sufficient "space" for the donor hematopoietic cells to expand in the recipient) and neuraminidase ([Neu] to enhance the trapping of i.v.-injected cells in the liver). Radiolabeled bone marrow cells (BMCs) were found to exclusively accumulate in the livers of the recipients as a result of the Neu treatment. Furthermore, hematopoietic progenitors (forming hematopoietic foci) in the accumulated BMCs were retained in the recipient livers for at least 18 days. C57BL/6 (B6) mice that had been transplanted with skins of BALB/c mice immediately after the injection of BALB/c BMCs showed a 90% skin graft survival rate over 400 days as a result of using the combination of injecting 50 mg/kg Bu into the B6 mice and treatment of the BALB/c BMCs with 0.25 U/ml Neu (50 Bu + 0.25 Neu). However, the survival rate significantly decreased when either the Bu or Neu treatment was omitted. In tolerant recipients, microchimerism was observed in the various hematolymphoid organs. T cells collected from the tolerant recipients suppressed proliferative responses to the donor-alloantigens but enhanced the production of Th2 and Th3 cytokines. These findings suggest that the enhanced retention of donor BMCs in the recipient livers as a result of the Bu and Neu treatments efficiently induces tolerance induction. Therefore, this "single-day protocol" would be of great advantage for human organ transplantation.

Tolerance induction across Mls and minor histocompatibility complex by inhibiting activation of T helper type 1 in early period

We have previously succeeded in inducing persistent donor-specific tolerance across Mls plus multiple minor histocompatibility barriers by portal venous (p.v.) injection of donor spleen or bone marrow cells plus cyclophosphamide (CY) treatment. Microchimerism was established in the lymph-hemopoietic organs of the tolerant recipients. However, the mechanisms, particularly the roles of CY in the tolerance induction, have not been clarified. We examined the tolerance induction using other anti-mitotic agents and evaluated the in vitro proliferative responses and cytokine expression of T cells from the recipients after stimulation with donor alloantigens. The administration of not only CY but also mitomycin C (MMC) and cytosin arabinoside (Ara C) elicited a prolongation of skin graft survival. CY induced tolerance when it was administered 2 days after the p.v. injection, but not immediately or 4 days after the p.v. injection. T cells collected from the tolerant recipients showed no proliferative responses as a result of stimulation with donor alloantigens whereas the responses of T cells from non-tolerant recipients were significantly enhanced. Interferon-gamma (IFNgamma) was extensively expressed in the non-tolerant T cells from 24 to 48 h after the stimulation with donor alloantigens. In contrast, the expression of IFNgamma was observed in the tolerant T cells from 72 h after the stimulation. Also, the tolerant T cells showed the expression of interleukin-10 (IL-10) and transforming growth factor-beta 1 (TGF-beta1) from 72 h after the stimulation whereas the non-tolerant T cells did not. These data suggest that CY, when administered 2 days after the p.v. injection, induces persistent tolerance by inhibiting T helper type 1 (Th1) activity in the early period but not the Th1 activity in the later periods.

Transplant tolerance modifying antibody to CD200 receptor, but not CD200, alters cytokine production profile from stimulated macrophages

Increased C57BL/6 allograft survival following donor-specific dendritic cell (DC) portal vein (pv) pre-transplant immunization of C3H mice is associated with increased expression of the molecule CD200 on DC, delivery of suppressive signals by CD200(r+) macrophages, and polarization in cytokine production towards type-2 cytokines. Infusion of anti-mouse CD200 monoclonal antibody abolishes these effects. We have used whole Ig, and F(ab')(2) fragments, of anti-CD200 and anti-CD200(r) mAb to explore the relative signaling role of CD200(+) versus CD200(r+) cells in suppression of type-1 cytokine production in mixed leukocyte cultures (MLC), and enhanced graft survival in vivo. Simple neutralization of CD200 [even by F(ab')(2) antibody] reversed CD200-mediated suppression. However, only whole anti-CD200(r) antibody was effective in stimulating suppression from CD200(r+) cells. Suppression of cytokine induction following cross-linking of CD200(r+) cells in vitro was attenuated by anti-IL-6 mAb. Our data are consistent with the hypothesis that CD200(r) itself delivers the crucial intracellular signal leading to immunosuppression, a feature likely of importance in autoimmunity and transplantation.

Preparation and functional properties of polyclonal and monoclonal antibodies to murine MD-1

Rabbits, rats and hamsters were immunized with KLH-coupled synthetic peptide sequences of the murine MD-1 molecule. Serum from immunized animals bound in Western gels to a 25 KDa protein extracted from LPS stimulated mouse spleen cells, as did a rat hybridoma (SH1.2.47) prepared from peptide-immunized rats. CHO cells transfected with a plasmid cDNA construct encoding murine MD-1, the target antigen for the antibodies in question, were also stained (in FACS) by the same antibodies. Patching and capping of the antigen(s) detected by any one of these sera abolished binding of all antibodies in subsequent FACS analysis, consistent with the hypothesis that they all detected the same antigen. In a final study to assess the possible involvement of MD-1 in regulation of cell activation for cytokine production following allostimulation, we found that all of the antibodies inhibited IL-2 and IFNgamma production, while enhancing IL-4 and IL-10 production, in mixed leukocyte reactions (MLR) in vitro.

Implantation of xenografts into parkinsonian rat brain after portal venous administration of xenogeneic donor spleen cells

Object. The purpose of the present study was to examine the effect of pretransplantation portal venous immunization with ultraviolet B (UVB)—treated donor spleen cells on neural xenograft transplantation.

Methods. Cells from a murine catecholaminergic cell line derived from the B6/D2 F1 mouse, CATH.a, were used as a xenograft. Thirty hemiparkinsonian rats were divided into three different treatment groups. Group 1 received saline in the dopamine-denervated striatum; Group 2 received xenograft cells; and Group 3 received portal venous administration of UVB-irradiated B6/D2 F1 splenocytes 7 days before receiving xenograft cells. Xenograft function was determined by reviewing apomorphine-induced rotation at 2-week intervals, and xenograft survival was examined at 4 and 12 weeks after transplantation by immunohistochemical staining for murine tyrosine hydroxylase (THase). Rotational behavior was improved in both xenograft-transplanted groups (Groups 2 and 3); however, the animals in Group 3 displayed a significantly reduced rotational behavior compared with Group 2. In Group 2, many inflammatory cells and a few THase-positive cells were found at the graft sites 4 weeks after transplantation. In Group 3, however, a large number of THase-positive cells were found with few inflammatory cells. The THase-positive cells disappeared in the Group 2 rats at 12 weeks, but remained in Group 3 animals. In Group 3 rats proliferation of spleen cells in a mixed lymphocyte reaction was suppressed in a donor-specific fashion.

Conclusions. This work demonstrates improved neural xenograft survival and function by pretransplantation portal venous immunization with UVB-irradiated xenogeneic donor splenocytes. On the basis of these findings, the authors suggest the possibility of creating donor-specific immunological tolerance in the brain by administration of xenogeneic donor lymphocytes via the portal vein.

Induction of immune hyporesponsiveness after portal vein immunization with ovalbumin

BACKGROUND

Previous work has demonstrated prolonged allograft survival after donor-specific portal vein immunization before the transplantation. The purpose of this study was to examine the potential mechanism of portal vein-induced hyporesponsiveness after portal vein immunization with the soluble protein ovalbumin.

METHODS

Balb/c mice were immunized with a portal vein injection of ovalbumin. After the immunization, in vivo delayed-type hypersensitivity response and in vitro proliferative response of ovalbumin-specific T cells were assessed to determine host immune response. Type 1 (IL-2, IL-12, IFN-gamma) and type 2 (IL-4, TGF-beta) regulatory cytokines were assessed by semiquantitative reverse transcriptase polymerase chain reaction. Sera anti-ovalbumin IgG, IgG1, and IgG2a were measured by enzyme-linked immunosorbent assay, and the antigen-presenting ability of liver nonparenchymal cells (NPCs) was assessed by T-cell proliferation to ovalbumin in vitro.

RESULTS

There was significant inhibition of ovalbumin-specific delayed-type hypersensitivity and T-cell proliferation in portal vein-immunized mice compared with intraperitoneal-immunized or control mice. Reverse transcriptase polymerase chain reaction analysis results showed that lymphocytes from portal vein-immunized mice exhibited decreased type 1 and increased type 2 cytokine messenger RNA expression compared with intraperitoneal-immunized or control animals. The type 2 cytokine response of lymphocytes from ovalbumin portal vein-immunized mice correlated with increased sera ovalbumin-IgG1 and decreased IgG2a. The results of an antigen-presenting assay revealed that liver NPCs were deficient antigen-presenting cells compared with adherent cells from heart or spleen.

CONCLUSIONS

Processing of ovalbumin by hepatic NPCs results in hyporesponsiveness to ovalbumin by an impaired type 1 cytokine response and a preferential shift toward a type 2 cytokine response, possibly because of defective antigen presentation by hepatic NPCs. Intrahepatic processing of antigen may play an important role in the development of strategies to reduce host immunoreactivity against transplanted allografts.

Receptor engagement on cells expressing a ligand for the tolerance-inducing molecule OX2 induces an immunoregulatory population that inhibits alloreactivity in vitro and in vivo

Increased survival of C57BL/6 renal allografts following portal vein donor-specific pretransplant immunization of C3H mice is associated with increased expression of the molecule OX2 seen on host dendritic cells, along with a marked polarization in cytokine production from lymphocytes harvested from the transplanted animals, with preferential production of IL-4, IL-10, and TGF-beta on donor-specific restimulation in vitro, and decreased production of IL-2, IFN-gamma, and TNF-alpha compared with non-portal vein-immunized control transplanted mice. The increased renal allograft survival and the altered cytokine production are abolished by infusion of anti-mouse OX2 mAb (3B6). Infusion of a soluble OX2:Fc immunoadhesin can itself produce significant prolongation of xeno- and allografts in mice. We have used FITC-conjugated OX2:Fc to characterize cells expressing a ligand (OX2L) for OX2, and provide evidence that subpopulations of LPS-stimulated splenic macrophages, Con A-activated splenic T cells, and the majority (>80%) of gammadeltaTCR(+) T cells express this ligand. We show below that F4/80(+), OX2L(+) splenic macrophages, admixed with OX2:Fc, represent a potent immunosuppressive population capable of causing more profound inhibition of alloreactivity in vitro or in vivo than that seen using either OX2:Fc or OX2(+) (or OX2L(+)) cells alone. Immunoregulation by this OX2L(+) population occurs in an MHC-restricted fashion.

Evidence for persistent expression of OX2 as a necessary component of prolonged renal allograft survival following portal vein immunization

Following portal vein (pv) pretransplant immunization of C3H mice, there is an early (within 2 days) increase in expression of the molecule OX2 seen on host dendritic cells (DC), along with increased survival of C57BL/6 renal allografts transplanted within 24 h of pv immunization. In addition, there is a marked polarization in cytokine production from lymphocytes harvested from the transplanted animals, with preferential production of IL-4, IL-10, and TGFbeta on donor-specific restimulation in vitro, and decreased production of IL-2, IFN-gamma, and TNFalpha compared with non-pv-immunized control transplanted mice. Both the increased renal allograft survival and the altered cytokine production are abolished by infusion of anti-mouse OX2 monoclonal antibody (3B6), even when antibody infusion is begun as late as 10 days following transplantation. Quantitative PCR analysis independently shows that OX2 expression is increased in the spleen and liver of transplanted mice as late as 21 days following pv immunization. In vitro studies with an OX2:Fc immunoadhesion had suggested that immunosuppression induced by this soluble form of the OX2 molecule was dependent primarily upon an early (OX2-dependent) signal. This discrepancy between in vivo and in vitro data possibly reflects a role for OX2 in the in vivo recruitment of other (immunregulatory) cells. Consistent with this hypothesis, regardless of the time (posttransplantation) of in vivo infusion of anti-OX2 antibody, within 2 days we observed a decline in the functional activity of a previously characterized immunoregulatory gammadeltaTCR(+) cell population, which can be monitored by its ability to regulate cytokine production in vitro.

Synergy in induction of increased renal allograft survival after portal vein infusion of dendritic cells transduced to express TGFbeta and IL-10, along with administration of CHO cells expressing the regulatory molecule OX-2

Dendritic cells (DC), generated from C57BL/6 mouse bone marrow cells cultured with GM-CSF and IL-4 for 9 days, were engineered to express constitutively the cytokines TGFbeta, IL-10, and IL-12, using adenovirus vectors constructed using an E1-deleted replication-deficient recombinant adenovirus carrying the appropriate cDNA for the relevant cytokines (Ad-TGFbeta, Ad-IL-12, or Ad-IL-10). C3H mice receiving nontransduced DC or pretransplant infusion of DC-Ad-LacZ showed increased survival of C57BL/6 renal grafts relative to that of control nonimmunized mice. Transfusion of Ad-IL-12-transduced DC abolished this increased survival, leading to a graft survival equivalent to that of controls with no DC. Optimal graft survival was seen in the group receiving a mixture of DC transduced with constructs for both IL-10 and TGFbeta. There was a correlation between increased graft survival and both inhibition of the induction of CTL and enhancement of a polarization to produce type-2 cytokines (IL-4, IL-10, and TGFbeta) on antigen-specific restimulation in vitro. These effects were more pronounced following concomitant infusion of CHO cells transfected with a full-length cDNA for murine OX-2.

Prolongation of allograft survival by Nippostrongylus brasiliensis is associated with decreased allospecific cytotoxic T lymphocyte activity and development of T cytotoxic cell type 2 cells

BACKGROUND

We have demonstrated that infection with Nippostrongylus brasiliensis (Nb), which induces strong type 2 responses, prolongs kidney allograft survival in rats. Here, we confirm that this effect is not species-specific and address immune modulation in allospecific T-cell responses mediated by nematode infection.

METHODS

C57BL/6 mice were injected with Nb or phosphate-buffered saline. Four days later, mice were transplanted with BALB/c hearts and graft survival was assessed. In other experiments, Nb-infected mice were immunized with BALB/c spleen cells and allospecific T-cell responses were determined in vitro.

RESULTS

In this study, we show that Nb prolongs cardiac allograft survival in mice. Further, spleen T cells from Nb-infected, allo-immunized mice exhibit reduced allospecific cytotoxic T-lymphocyte activity. In contrast, allospecific proliferation of T cells in the mixed lymphocyte reaction was not reduced by Nb, ruling out immunosuppression as the mechanism of Nb-induced allograft survival. Nb infection induced IL-4 and IL-6 and inhibited IFN-gamma production by T cells in response to allo-antigen. Furthermore, anti-IL-4 treatment reduced allospecific T-cell proliferation from Nb-infected but not control mice, indicating that type 2 allospecific T cells develop in the presence of Nb. We also double-stained T cells for CD8 and IL-4 and showed that Nb induces an 8-fold increase in Tc2 cell numbers.

CONCLUSIONS

These results are consistent with a hypothesis that Nb mediates prolongation of allograft survival through induction of type 2 immunity, including the development of regulatory Tc2 cells, and subsequent inhibition of allospecific cytotoxic T-lymphocyte activity.

Assessment of immunologic status of liver transplant recipients by peripheral blood mononuclear cells in response to stimulation by donor alloantigen

OBJECTIVE

To determine whether there is a role for assessing peripheral blood mononuclear cell (PBMC) cytokine patterns as a means of measuring the immunologic and clinical status of liver transplant recipients.

SUMMARY BACKGROUND DATA

The role of assessing cytokine patterns in the prediction of clinical graft rejection or acceptance remains unclear. The purpose of this study was to examine the cytokine profiles of PBMC stimulated in vitro with donor alloantigen and to correlate prospectively the data with clinical assessment of graft status in orthotopic liver transplant (OLT) recipients.

METHODS

PBMCs from OLT recipients were examined for proliferation and cytokine mRNA expression after stimulation by donor alloantigen, third-party alloantigen, or phytohemagglutinin (PHA). mRNA extracted from PBMC was amplified by reverse transcriptase-polymerase chain reaction with oligospecific primer pairs for interleukin (IL)-2, IL-4, IL-6, IL-10, interferon (IFN) gamma, tumor necrosis factor (TNF) alpha and transforming growth factor (TGF) beta. Results were prospectively correlated with each patient's allograft status.

RESULTS

Increased IL-4 and TGF-beta and decreased IL-2, IFNgamma, and TNF-alpha mRNA expression by PBMCs in response to donor alloantigen stimulation predicted immunologic graft stability over a minimum 60-day interval compared with mRNA expression of PBMCs from patients with established rejection or those who experienced a rejection episode within a 30-day period (p < 0.05). Stimulation of recipient PBMCs with third-party alloantigens or PHA yielded similar but less specific results. PBMC proliferation to varying antigenic stimulation did not correlate with clinical graft status, nor did cytokine production by unstimulated PBMC.

CONCLUSIONS

Prospective assessment of cytokine expression by PBMC from OLT recipients in response to stimulation by donor alloantigen is helpful for predicting the clinical status of the allograft and may be useful in the development of more precise immunologic monitoring protocols.

An Immunoadhesin Incorporating the Molecule OX-2 Is a Potent Immunosuppressant That Prolongs Allo- and Xenograft Survival

We have established that, in mice receiving donor-specific immunization by the portal vein, the increased graft survival seen is associated with the increased expression of a molecule (OX-2) on a subpopulation of dendritic cells (DC), and polarization of cytokine production to type 2 cytokines on Ag-specific restimulation of cells from these mice. Furthermore, infusion of a mAb to OX-2 blocks both the increased graft survival and the altered cytokine production seen. We have constructed an immunoadhesin in which the extracellular domain of OX-2 is linked to the murine IgG2a Fc region, and we have expressed this molecule (OX-2:Fc) in a eukaryotic (baculovirus) expression system. Incubation of lymphocytes with 50 ng/ml OX-2:Fc inhibits a primary mixed lymphocyte reaction in vitro, as assayed by proliferation and induction of cytotoxic T cells, and also alters cytokine production with decreased IL-2 (IFN-γ) production and increased IL-4 (IL-10) production. Similarly, in vivo infusion of OX-2:Fc promotes increased allo- and xenograft (both skin and renal grafts) survival and decreases the Ab response to sheep erythrocytes. Our data suggest this molecule might have clinical importance in allo- and xenotransplantation.

Acceptance of skin allografts in pigs by portal venous injection of donor bone marrow cells

OBJECTIVE

To confirm in pigs whether a new method for organ allografts, originally established in mice by the authors, might be applicable to humans.

SUMMARY BACKGROUND DATA

The authors recently established a new method for organ allografts in mice that includes the injection of donor bone marrow cells (BMCs) using the portal vein (PV), followed by the administration of cyclosporin A (CsA) on days 2 and 5, and the intravenous injection of BMCs on day 5. In the present study, they modify this method (a single-day protocol) and apply it to pigs.

METHODS

Allogeneic BMCs of donor pigs were injected using the PV (a superior mesenteric vein). The skin grafting was carried out on the day of the PV injection. The recipient pigs received donor grafts, autologous grafts, and third-party grafts at the same time. In addition, an open wound was made as the epithelized control. Full-thickness skin grafts were harvested from the dorsal wall of the donors. CsA (10 mg/kg) was injected intramuscularly into recipient pigs on days 2 and 5 after the PV injection.

RESULTS

One hundred percent of skin grafts survived for >300 days when donor BMCs were injected using the PV (n = 6). However, the skin grafts of the three pigs that had received BMCs using the intravenous route were rejected within 3 to 4 weeks after transplantation. The third-party skin grafts showed necrotic changes on day 21 after transplantation.

CONCLUSIONS

One hundred percent of skin allografts can be obtained, even in pigs, by injecting donor BMCs using the PV, carrying out skin allografts, and administering CsA on days 2 and 5. This single-day protocol would be of great advantage for human organ transplantation.

Preparation and functional properties of monoclonal antibodies to human, mouse and rat OX-2

We have prepared mouse and rat hybridomas to a 43-kDa molecule expressed in the thymus, on a subpopulation of dendritic cells, and in the brain, in mammalian tissue derived from mouse, rat and human. Using CHO cells transiently transfected with adenovirus vector(s) expressing a cDNA construct for the relevant OX-2 gene, we show these monoclonal antibodies (Mabs) detect a molecule encoded by this construct (rat OX-2 (rOX-2), mouse OX-2 (mOX-2) and human OX-2 (huOX-2), respectively). Furthermore, at least some of the anti-rat Mabs detect determinants expressed on the murine OX-2 molecule, as we predicted in an earlier publication. Previous studies have implied that this molecule might serve an important role in regulation of cell signaling for cytokine production. Using one-way mixed leukocyte reactions we show that when cells are cultured in the presence of the species-specific Mab, cytokine production becomes polarized 'away from' type-2 cytokine production, with preferentially increased expression of type-1 cytokine production.

Evidence That an OX-2-Positive Cell Can Inhibit the Stimulation of Type 1 Cytokine Production by Bone Marrow-Derived B7-1 (and B7-2)-Positive Dendritic Cells

We reported that hepatic mononuclear, nonparenchymal cells (NPC) can inhibit the immune response seen when allogeneic C57BL/6 dendritic cells (DC) are incubated with C3H spleen responder cells. Cells derived from these cultures transfer increased survival of C57BL/6 renal allografts in C3H mice. We also found that increased expression of OX-2 on DC was associated with inhibition of cytokine production and renal allograft rejection. We explored whether inhibition by hepatic NPC was a function of OX-2 expression by these cells. Fresh C57BL/6 spleen-derived DC were cultured with C3H spleen responder cells and other putative coregulatory cells. The latter were derived from fresh C3H or C57BL/6 liver NPC, or from C3H or C57BL/6 mice treated for 10 days by i.v. infusion of human Flt3 ligand. Different populations of murine bone marrow-derived DC from cultures of bone marrow with IL-4 plus granulocyte-macrophage-CSF were also used as a source of putative regulator cells. Supernatants of all stimulated cultures were examined for functional expression of different cytokines (IL-2, IL-4, IFN-γ, and TGFβ). We found that fresh C57BL/6 splenic DC induced IL-2, not IL-4, production. Cells from the sources indicated inhibited IL-2 and IFN-γ production and promoted IL-4 and TGFβ production. Inhibition was associated with increased expression of OX-2 on these cells, as defined by semiquantitative PCR and FACS analysis. By size fractionation, cells expressing OX-2 were a subpopulation of NLDC145+ cells. Our data imply a role for cells expressing OX-2 in the regulation of induction of cytokine production by conventional allostimulatory DC.

Donor-specific stimulation of peripheral blood mononuclear cells from recipients of orthotopic liver transplants is associated, in the absence of rejection, with type-2 cytokine production

In this study, we examined the cytokine production by human peripheral blood mononuclear cells (PBM) from recipients of orthotopic liver transplants which had been stimulated by donor-specific alloantigen. Levels of interleukin (IL)-2, IL-4, interferon (IFN)-gamma, IL-10 and transforming growth factor (TGF)-beta produced in vitro from PBM of 15 transplant recipients at 5-7 months post transplantation were analysed after donor-specific, third-party, or non-specific stimulation. Mononuclear cell proliferation in response to stimulation and cytokine mRNA from the cell cultures were assayed. Donor-specific antigen was obtained from donor spleen cells which had been obtained and frozen in liquid nitrogen at the time of organ retrieval. Third-party restimulation used equivalent numbers of spleen cells pooled from the other 14 organ donors. Cytokine production was correlated with the clinical condition of the patient, including biopsy results when available, and biochemical data. The data show a highly significant correlation between the donor-specific- and third-party- stimulated IL-4 and IL-10 production from recipient PBM with stable liver graft function as assessed by histopathology and/or biochemistry. This correlation was independent of level of immunosuppression. These data strongly support a role for IL-4 and/or IL-10 in the induction and/or maintenance of tolerance to human liver allografts. Measurement of the levels of these cytokines from recipient PBM after donor-specific antigen stimulation in vitro may be a useful test for monitoring for acute allograft rejection.

A role for persisting antigen, antigen presentation, and ICAM-1 in increased renal graft survival after oral or portal vein donor-specific immunization

BACKGROUND

We studied the mechanism behind increased renal allotransplant survival when C3H mice received donor-specific portal vein or oral immunization with C57BL/6 cells. Both regimens lead to donor-specific increased graft survival, in association with decreased production of cytotoxic T lymphocytes and altered cytokine production from host lymphocytes (decreased interleukin [IL]-2 production; increased IL-4, IL-10, and transforming growth factor-beta).

METHODS

We examined a role for persistent donor-derived antigen, in association with host dendritic cells, as well as a role for intercellular adhesion molecule-1 (ICAM-1), in the maintenance of unresponsiveness in host C3H spleen cells to donor antigen. We investigated whether there was a cooperative interaction between donor dendritic cells (DC) and host hepatic mononuclear cells in the induction of immunoregulation in C3H cells.

RESULTS

In mice with surviving renal grafts, donor antigen, in association with host DC, induced the recall of cytotoxicity from C57BL/6 immune C3H spleen cells and IL-4 but not IL-2 production, despite the decreased cytotoxicity seen in the renal transplant recipients themselves. Fresh donor DC induced IL-2 but not IL-4 production. Blocking expression of ICAM-1 on donor grafts, either with anti-ICAM-1 monoclonal antibodies after renal grafting or using grafts from ICAM-1 "knockout" mice, led to further increased survival. Cultured C3H responder spleen cells, incubated with C57BL/6 DC and C3H hepatic cells, transferred hyporesponsiveness to C57BL/6 cells in vitro and in vivo (as assayed by survival of C57BL/6 renal allografts).

CONCLUSIONS

Our data suggest a role for ICAM-1, persistent donor antigen (on host DC), and accessory hepatic monocytes in the induction and maintenance of tolerance after portal vein immunization.

A strategy for organ allografts without using immunosuppressants or irradiation

A strategy to achieve regular and long lasting organ and tissue allografts without using immunosuppressants and/or irradiation has been established for mice. One hundred percent of skin allografts can be induced to survive >350 days after transplantation if spleen cells from the same donors are first injected into the portal vein of the recipients. The mechanisms underlying this long-term tolerance induction can be described as follows: (i) donor T cells from the spleen of the donor facilitate the acceptance of the allogeneic engraftment, (ii) donor-specific anergy is induced in the cytotoxic T-lymphocytes of the recipients, (iii) T helper type 2 cells become the dominant T cells in the recipients that are accepting the skin transplants, and (iv) a lasting chimerism (microchimerism) is established in these recipients. This strategy, perhaps with minor modifications, might permit one also to overcome major barriers to organ allografting in humans. If this were the case, it could represent production of long lasting immunologic tolerance without need for irradiation or cytotoxic chemo-preparative regimen and as such could greatly facilitate allotransplantation free of episodes of chronic or acute rejection or toxic and damaging preparatory regimens.

Increased expression of the novel molecule OX-2 is involved in prolongation of murine renal allograft survival

BACKGROUND

Portal venous (p.v.) peritransplant immunization with dendritic cells from bone marrow cultures, along with cyclosporine (10 mg/kg), produces antigen-specific increased renal allograft survival compared with recipients receiving intravenous (i.v.) immunization. Increased survival is associated with altered cytokine production from recipient T cells restimulated with donor antigen. We used a suppressive subtractive hybridization approach to explore a role in the regulation of transplant rejection for other genes differentially expressed after p.v. immunization.

METHODS

Subtractive hybridization was performed using tissue from p.v. and i.v. immunized mice and a novel polymerase chain reaction-based approach. A gene-bank search was used to identify the source of the differentially expressed cDNAs. One product, the mouse homologue of rat OX-2, was further analyzed using Western gels and FACS analysis of dendritic cells (NLDC145+) isolated from p.v.-immunized mice.

RESULTS

Eighty cDNA clones were obtained by suppressive subtractive hybridization. Differential expression was confirmed in Northern RNA blots. One clone showed sequence homology to a gene encoding a molecule on rat dendritic cells (MRC OX-2), with homology to genes encoding the costimulatory molecules CD80 (B7-1) and CD86 (B7-2). In p.v.-immunized mice, a monoclonal antibody to the rat OX-2 molecule identified, by Western blot analysis, increased expression of a molecule with molecular weight (43 kDa) analogous to rat MRC-OX-2; labels (by FACS analysis) indentified increased numbers of a population of cells staining with NLDC145; and blocks indentified increased graft survival.

CONCLUSION

Our data suggest that OX-2 is functionally important in the increased graft survival seen in p.v.-immunized mice receiving renal allografts.

Analysis of cytokine production and V beta T-cell receptor subsets in irradiated recipients receiving portal or peripheral venous reconstitution with allogeneic bone marrow cells, with or without additional anti-cytokine monoclonal antibodies

Irradiated (800 rads) AKR mice received intravenous (i.v.) reconstitution with a mixture of B10.BR T-depleted bone marrow cells and spleen cells. Only in groups of mice treated additionally with i.v. cyclophosphamide (Cy; 150 mg/kg), 24 hr before transplantation, was long-term (> 60% at 50 days) survival seen. In mice receiving only irradiation all animals died by 30 days post-transplantation. Histological changes consistent with graft-versus-host disease (GVHD) were seen in the liver of reconstituted mice at 30 days, along with an organ-specific increase in V beta 3 T-cell receptor-positive (TCR+) cells. No such increase in V beta 3 TCR+ cells was seen in the spleen from the same mice. These data are consistent with a tissue antigen-driven expansion of V beta 3 TCR+ cells associated with GVHD in the liver in this model. When we analysed cytokine production in vitro from CD3+ cells restimulated with 'host' (AKR) antigen-presenting cells (APC), we found a transition in cytokine production from preferential synthesis of type-1 cytokines [interleukin-2 (IL-2) and interferon-gamma (IFN-gamma)] at early times (day 15) post-reconstitution to increased production of type-2 cytokines [IL-4, transforming growth factor-beta (TGF-beta) and IL-10] at later times (day 30) post-reconstitution in Cy-treated recipients. Animals not receiving Cy did not show this 'switch' in cytokine production at later time points. We have observed a similar polarization in cytokine production, along with increased graft survival, in recipients of vascularized and non-vascularized allografts after portal venous (p.v.), but not i.v., pretransplant donor-specific immunization. We next studied AKR mice receiving 800 rads and subsequently reconstituted with B10.BR stem cells via the p.v. route. Again these mice showed prolonged survival (> 50% at 50 days), with polarization to IL-4, IL-10 and TGF-beta on restimulation of CD3+ cells in vitro at 30 days post-transplant and increased V beta 3 TCR+ cells in the liver. Infusion of anti-IL-12 monoclonal antibodies into irradiated mice receiving i.v. cell reconstitution produced a similar pattern of changes to those seen after p.v. reconstitution, while a combination of anti-IL-10 and anti-TGF-beta monoclonal antibodies reversed the changes seen after p.v. reconstitution. These data are consistent with an important role for differential cytokine production in the regulation of GVHD following allogeneic bone marrow transplantation.

Effect of donor-specific splenocytes via portal vein and FK506 in rat small bowel transplantation

BACKGROUND

To investigate the role of the liver in immune responses after small bowel transplantation, donor-specific splenocytes were infused perioperatively, via the portal vein, in a rat heterotopic small bowel transplant model.

METHODS

Heterotopic small bowel transplantation between the fully allogenic Brown Norway (BN) (RT1n) and Lewis (RT1[1]) strain rats were performed. We prepared donor splenocytes from BN or third-party WKA (RT1k) rat spleens for Lewis hosts and injected the splenocytes perioperatively via the host portal vein or the systemic vein. The hosts were treated with a short course of the immunosuppressive agent, FK506 (0.5 mg/kg, 0-3 days postoperatively), following the experimental protocols.

RESULTS

Untreated Lewis hosts rejected BN small bowel grafts at 5.4+/-0.9 days (n=8). BN splenocytes given alone caused fatal graft-versus-host disease in six of eight animals, and two others died from graft rejection. FK506 alone did not significantly prolong graft survival (6.3+/-1.0 days, n=10). However, BN splenocytes injected via the portal vein, combined with FK506, prolonged graft survival to 12.7+/-2.1 days (n=12, P < 0.01) and 10 of 12 rats survived more than 70 days. This was donor antigen specific. BN splenocytes administered systemically caused fatal graft-versus-host disease in all recipients, and FK506 did not ameliorate this. Histologic findings of graft rejection were remarkably mild in the recipients of the combined therapy, compared with the recipients that were given FK506 alone. Down-regulation of one-way mixed lymphocyte reaction to BN splenocytes was observed in the splenocytes of the tolerant hosts.

CONCLUSIONS

Combined administration of donor splenocytes and FK506 reduced allograft rejection and prolonged survival in this rat model of small bowel transplantation.