A subset of gamma delta T-cell receptor-positive cells produce T-helper type-2 cytokines and regulate mouse skin graft rejection following portal venous pretransplant preimmunization

Differentiation and functional plasticity of gamma-delta (γδ) T cells under homeostatic and disease conditions

Gamma-delta (γδ) T cells are a heterogeneous population of immune cells, which constitute <5% of total T cells in mice lymphoid tissue and human peripheral blood. However, they comprise a higher proportion of T cells in the epithelial and mucosal barrier, where they perform immune functions, help in tissue repair, and maintaining homeostasis. These tissues resident γδ T cells possess properties of innate and adaptive immune cells which enables them to perform a variety of functions during homeostasis and disease. Emerging data suggest the involvement of γδ T cells during transplant rejection and survival. Interestingly, several functions of γδ T cells can be modulated through their interaction with other immune cells. This review provides an overview of development, differentiation plasticity into regulatory and effector phenotypes of γδ T cells during homeostasis and various diseases.

Bibliometric Analysis of Dendritic Epidermal T Cell (DETC) Research From 1983 to 2019

Dendritic epidermal T cells (DETC) are a group of immune cells expressing canonical γδ TCR in the murine epidermis. Similar to γδ T cells in the human epidermis, DETC serve an important barrier cell in the skin and participate in skin immune surveillance, immune regulation, skin homeostasis, tissue protection, and other activities. Since its discovery in 1983, research on DETC has grown rapidly and unevenly. To evaluate DETC research trends and map the DETC knowledge structure, we have applied bibliometric methods and techniques. A total of 384 DETC-related articles obtained from the Scopus database published between 1983 and 2019 were analyzed using indicators of publication and citation metrics, country and international cooperation, author and co-authorship, and keyword co-occurrence cluster. The present research status, the emerging global trends and the future development direction are also visualized and discussed. In summary, this study provides novel and useful data for the DETC research scientific community, and will help researchers explore DETC more intuitively and effectively.

The complex existence of γδ T cells following transplantation: the good, the bad and the simply confusing

Gamma delta (γδ) T cells are a highly heterogeneous population of lymphocytes that exhibit innate and adaptive immune properties. Despite comprising the majority of residing lymphocytes in many organs, the role of γδ T cells in transplantation outcomes is under‐researched. γδ T cells can recognise a diverse array of ligands and exert disparate effector functions. As such, they may potentially contribute to both allograft acceptance and rejection, as well as impacting on infection and post‐transplant malignancy. Here, we review the current literature on the role and function of γδ T cells following solid organ and hematopoietic stem cell transplantation.

Deciphering the Contribution of γδ T Cells to Outcomes in Transplantation

γδ T cells are a subpopulation of lymphocytes expressing heterodimeric T-cell receptors composed of γ and δ chains. They are morphologically and functionally heterogeneous, innate yet also adaptive in behavior, and exhibit diverse activities spanning immunosurveillance, immunomodulation, and direct cytotoxicity. The specific responses of γδ T cells to allografts are yet to be fully elucidated with evidence of both detrimental and tolerogenic roles in different settings. Here we present an overview of γδ T-cell literature, consider ways in which their functional heterogeneity contributes to the outcomes after transplantation, and reflect on methods to harness their beneficial properties.

Immunology of hepatic diseases during pregnancy

The mother's immune system has to adapt to pregnancy accepting the semi-allograft fetus and preventing harmful effects to the developing child. Aberrations in feto-maternal immune adaptation may result in disease of the mother, such as liver injury. Five pregnancy-associated liver disorders have been described so far, however, little is known concerning immune alterations promoting the respective disease. These liver disorders are pre-eclampsia, hemolysis, elevated liver enzymes, low platelet count (HELLP), acute fatty liver, hyperemesis gravidarum, and intrahepatic cholestasis of pregnancy. On the other hand, pre-existing autoimmune liver injury of the mother can be affected by pregnancy. This review intends to summarize current knowledge linking feto-maternal immunology and liver inflammation with a special emphasis on novel potential biomarkers.

Mechanisms of adaptation and progression in idiosyncratic drug induced liver injury, clinical implications

In the past decade our understanding of idiosyncratic drug induced liver injury (IDILI) and the contribution of genetic susceptibility and the adaptive immune system to the pathogenesis of this disease process has grown tremendously. One of the characteristics of IDILI is that it occurs rarely and only in a subset of individuals with a presumed susceptibility to the drug. Despite a clear association between single nucleotide polymorphisms in human leukocyte antigen (HLA) genes and certain drugs that cause IDILI, not all individuals with susceptible HLA genotypes develop clinically significant liver injury when exposed to drugs. The adaptation hypothesis has been put forth as an explanation for why only a small percentage of susceptible individuals develop overt IDILI and severe injury, while the majority with susceptible genotypes develop only mild abnormalities that resolve spontaneously upon continuation of the drug. This spontaneous resolution is referred to as clinical adaptation. Failure to adapt or defective adaptation leads to clinically significant liver injury. In this review we explore the immuno-tolerant microenvironment of the liver and the mechanisms of clinical adaptation in IDILI with a focus on the role of immune-tolerance and cellular adaptive responses.

γδ T Cell-Mediated Immune Responses in Disease and Therapy

The role of γδ T cells in immunotherapy has gained specific importance in the recent years because of their prominent function involving directly or indirectly in the rehabilitation of the diseases. γδ T cells represent a minor population of T cells that express a distinct T cell receptor (TCR) composed of γδ chains instead of αβ chains. Unlike αβ T cells, γδ T cells display a restricted TCR repertoire and recognize mostly unknown non-peptide antigens. γδ T cells act as a link between innate and adaptive immunity, because they lack precise major histocompatibility complex (MHC) restriction and seize the ability to recognize ligands that are generated during affliction. Skin epidermal γδ T cells recognize antigen expressed by damaged or stressed keratinocytes and play an indispensable role in tissue homeostasis and repair through secretion of distinct growth factors. γδ T cell based immunotherapy strategies possess great prominence in the treatment because of the property of their MHC-independent cytotoxicity, copious amount of cytokine release, and a immediate response in infections. Understanding the role of γδ T cells in pathogenic infections, wound healing, autoimmune diseases, and cancer might provide knowledge for the successful treatment of these diseases using γδ T cell based immunotherapy. Enhancing the human Vγ9Vδ2 T cells functions by administration of aminobisphosphonates like zoledronate, pamidronate, and bromohydrin pyrophosphate along with cytokines and monoclonal antibodies shows a hopeful approach for treatment of tumors and infections. The current review summarizes the role of γδ T cells in various human diseases and immunotherapeutic approaches using γδ T cells.

Characterization of γδ T cell subsets in organ transplantation

γδ T cells are innate-type lymphocytes that preferentially act as regulators of local effector immune responses. Recent reports found an altered distribution of the two main subpopulations of blood γδ T cells (Vδ1 and Vδ2) in operationally tolerant liver transplant recipients. Based on this, γδ T cells subset quantification was proposed as a biomarker of immunologic risk in liver transplantation. The specific characteristics of γδ T cell subsets in transplantation remain however unknown. We have investigated here the phenotype, repertoire and functional properties of γδ T cell subsets in a large population of allograft recipients. Our results indicate that alterations in the γδ T cell compartment are not restricted to tolerant liver recipients. In fact, most immunosuppressed liver and kidney recipients also display an enlarged peripheral blood γδ T cell pool mainly resulting from an expansion of Vδ1 T cells exhibiting an oligoclonal repertoire and different phenotypic and cytokine production traits than Vδ2 T cells. We propose that persistent viral infections are likely to contribute to these alterations. Our data provide novel insight in the biology of γδ T cells and a rationale for exploring these lymphocytes in more depth into the pathogenesis of viral infections in transplantation.

Cellular and molecular mechanisms of liver tolerance

The liver exhibits a distinctive form of immune privilege, termed liver tolerance, in which orthotopic liver transplantation results in systemic donor-specific T-cell tolerance, while antigens introduced either into hepatocytes or via the portal vein also cause tolerance. Here we argue that the fundamental mechanism driving liver tolerance is likely to be the continuous exposure of diverse liver cell types to endotoxin, derived from the intestinal bacteria. This exposure promotes the expression of a set of cytokines, antigen-presenting molecules, and costimulatory signals that impose T-cell inactivation, partly via effects on liver antigen-presenting cells. The evidence favors clonal deletion mechanisms and is consistent with a role for regulatory T cells but does not support either anergy or immune deviation as important factors in liver tolerance.

CD8 T cell of donor splenocyte mixed with bone marrow cells is more effective than CD4 T cell for induction of donor-specific tolerance in sublethally irradiated mice

BACKGROUND

We previously demonstrated that even a low dose of bone marrow cells (BMCs) established donor-specific tolerance if mixed with splenocytes (SPLCs). In this study, T-cell subsets CD4 (CD4SP) and CD8 (CD8SP) of donor SPLCs were investigated for their contribution to the enhancement of BMC engraftment leading to donor-specific tolerance in sublethally irradiated mice.

METHODS

Sublethally irradiated C57BL/6 recipient mice were intravenously injected BMCs mixing with CD4SP or CD8SP harvested from BALB/c donor mice. The degree of chimerism in the peripheral blood lymphocytes (PBLs) and in the SPLCs was analyzed using FACS, mixed lymphocyte reaction, and skin graft transplantation 3 months after injection.

RESULTS

Recipients injected with 3 x 10(6) donor BMCs admixed with 10 x 10(6) donor CD8SP established chimerism. However, recipients injected with the same dose of BMCs admixed with 5 x 10(6) CD4SP, 10 x 10(6) CD4SP, and 5 x 10(6) CD8SP did not established chimerism. CD8SP contained 44% of Ly6A/E (Stem Cell Antigen-1 (Sca-1))-positive cells based on FACS analysis, whereas only 6% of CD4SP were positive for Ly6A/E. MLR supernates of donor SPLCs chimeric mice using admixture with CD8SP dominated by Th2 cytokines. In contrast, mixting with MLR supernates from failed chimera showed dominant Th1 cytokines.

CONCLUSIONS

CD8SP seems to make a major contribution to enhance BMC engraftment and induce donor-specific tolerance. Ly6A/E (Sca-1)-positive cells need to be further investigated for their contribution to the establishment of chimerism.

CHEMOKINE EXPRESSION IN NERVE ALLOGRAFTS

OBJECTIVE

Chemokines (chemoattractant cytokines) play a major role in trafficking of cells to areas of inflammation. Infiltration of allograft tissues by immunocompetent cells is critical for rejection of donor tissues. The role of chemokines in nerve allograft rejection is not clear. We hypothesized that chemokines are responsible for attracting macrophages and T lymphocytes into nerve allograft tissue, initiating the graft rejection process.

METHODS

Lewis rats received 4-cm-long peroneal nerve allografts and isografts from ACI and Lewis rats, respectively. Twelve hours to 10 days after transplantation, grafts were removed and total cellular ribonucleic acid was extracted. Intragraft gene expression of several chemokines (cytokine-induced neutrophil chemoattractant, macrophage inflammatory protein [MIP]-2, monocyte chemoattractant protein-1, MIP-1 alpha, and regulated upon activation normal T-cell expressed and secreted [RANTES]) were analyzed by reverse transcription-polymerase chain reaction.

RESULTS

The cytokine-induced neutrophil chemoattractant was expressed in allografts and isografts at early time points (12 h to 6 d). Monocyte chemoattractant protein-1 messenger ribonucleic acid expression was similarly high in both isografts and allografts from 12 hours until 8 days after transplantation. MIP-1 alpha, MIP-2, and RANTES were expressed only in allografts. Kinetics of the neutrophil (MIP-2) and macrophage (MIP-1 alpha) chemokines revealed an early onset (12-24 h), a plateau from 1 to 4 days, and expression abruptly declining by Day 6. The lymphocyte chemoattractant RANTES had delayed kinetics, with a rise at Day 3, a peak at Day 4, and a gradual decline.

CONCLUSION

Induction of specific chemokine genes precedes nerve allograft infiltration by immunocompetent cells. MIP-1 alpha, MIP-2, and RANTES may be responsible for recruiting macrophages, granulocytes, and lymphocytes, respectively, to the rejecting allograft. In future studies, blockade of these specific chemokines or their receptors may prove to delay or prevent nerve allograft rejection.

Impact of portal venous pancreas graft drainage on kidney graft outcome in simultaneous pancreas-kidney recipients reported to UNOS

Clinical data on the potential immunologic impact of portal (PD) vs. systemic (SD) venous pancreas graft drainage on outcome remains controversial. We reviewed the UNOS database to study the effect of PD vs. SD on the incidence of kidney graft rejection and survival in first cadaveric simultaneous pancreas-kidney (SPK) recipients transplanted 1994-2001. We studied three groups: all SPK (n=6629, 13% PD) (group I), SPK on tacrolimus (n=3563, 17% PD) (group II), and SPK on tacrolimus performed at centers with significant PD experience (n=948, 46% PD) (group III). The cumulative kidney graft rejection incidence for PD vs. SD was only significantly different in group I (for PD vs. SD, respectively: at 6 months, 31% vs. 36% [p=0.015]; at 1 year, 37% vs. 43% [p=0.006]). Kidney graft survival was similar in all groups for PD vs. SD. Multivariate analysis of group III showed only transplantation during the earlier era (1994-96), but not SD, to be an independent risk factor for kidney graft rejection. Portal venous pancreas graft drainage does not affect kidney graft rejection and survival in SPK recipients on tacrolimus. Our data suggests that the efficacy of current immunosuppressive protocols and increasing center experience are clinically much more relevant than any potential immunologic advantage of portal venous drainage in SPK recipients.

Induction of oral tolerance and the effect of interleukin-4 on murine skin allograft rejection

We studied the effect of oral and portal vein administration of alloantigens on mouse skin allograft survival. Graft receptor BALB/c mice received spleen cells (30, 90, 150 or 375 x 10(6)) from donor C57BL/6 mice intragastrically on three successive days, starting seven days before the skin graft. Allograft survival was significantly increased with the feeding of 150 x 10(6) allogeneic spleen cells by one gavage (median survival of 12 vs 14 days, P< or =0.005) or when 300 x 10(6) cells were given in six gavage (12 vs 14 days, P<0.04). A similar effect was observed when 150 x 10(6) spleen cells were injected into the portal vein (12 vs 14 days, P< or =0.03). Furthermore, prolonged allograft survival was observed with subcutaneous (12 vs 16 days, P< or =0.002) or systemic (12 vs 15 days, P< or =0.016) application of murine interleukin-4 (IL-4), alone or in combination with spleen cell injection into the portal vein (12 vs 18 days, P< or =0.0018). Taken together, these results showed that tolerance induction with spleen cells expressing fully incompatible antigens by oral administration or intraportal injection partially down-modulates skin allograft rejection. Furthermore, these findings demonstrated for the first time the effect of subcutaneous or systemic IL-4 application on allograft skin survival suggesting its use as a beneficial support therapy in combination with a tolerance induction protocol.

Interferon-gamma-inducing oral vaccination with Leishmania amazonensis antigens protects BALB/c and C57BL/6 mice against cutaneous leishmaniasis

The induction of oral tolerance against disease-inducing antigens has emerged as a feasible strategy to prevent immunopathologies. In this study, we investigated the effect of oral immunization with whole antigens of Leishmania amazonensis promastigotes (LaAg) on murine cutaneous leishmaniasis. We found that two oral doses with 100 microg LaAg rendered BALB/c and C57BL/6 mice more resistant against subsequent infection with L. amazonensis. The oral vaccine also partially protected BALB/c mice against Leishmania major infection. Unlike the oral route, hepatic immunization was without effect, indicating a requirement for antigen passage through the gut mucosa. Oral LaAg significantly impaired the capacity of infected BALB/c mice to mount a disease-associated hypersensitivity response, compatible with peripheral tolerization. Both IFN-gamma and IL-10, but not IL-4 were greatly elevated in the mesenteric lymph nodes whereas only IFN-gamma was increased in the peripheral lymph nodes, compatible with a TH1 cytokine response. Gamma delta TCR+ T cells may be an important component in antigenic sensitization of the gut mucosa since their depletion during oral immunization reverted protection. These results demonstrate for the first time the feasibility of using the oral route of immunization to induce protection against cutaneous leishmaniasis using a crude parasite antigen.

Intraportal donor bone marrow transplantation improves intestinal allograft survival in rats under FK506-based immunosuppression

Donor-specific immunosuppression is important in transplant surgery. We examined the effect of intraportal donor-specific bone marrow transplantation on heterotopic small bowel transplantation in the high responder rat combination, ACI to Lewis. The study comprised five treatment groups: untreated controls (group 1); FK506 alone (group 2); low-dose predonine + FK506 (group 3); high-dose predonine + FK506 (group 4); and intraportal donor-specific bone marrow transplantation + FK506 (group 5). Intraportal transplantation was performed pre-operatively and FK506 and predonine given post-operatively. Intestinal allograft survival and changes of intragraft cytokine expression were analysed using the reverse transcription polymerase chain reaction. Allograft survival (mean +/- SD) was lowest in group 1 and greatest in group 5. The group 5 treatment regimen also down-regulated interferon-gamma and interleukin-2 transcription in the transplanted intestine. Intraportal donor bone marrow transplant combined with FK506 immunosuppression was found therefore to be the most beneficial treatment regimen.

Gammadelta T cells and interleukin-6 levels could provide information regarding the progression of human renal allograft

We have determined the percentage of alphabeta and gammadelta T cells by flow cytometry as well as serum interleukin-6 (IL-6) and soluble interleukin-6 receptor (sIL-6R) levels by enzyme-linked immunosorbent assay in kidney allograft recipients with acute, chronic or stable graft evolution. The percentage of CD4 and CD8 T cells in transplanted patients was lower than in the control group (P < 0.001) with the exception of CD8 gammadelta T cells from patients with stable evolution (P > 0.05). The serum levels of IL-6 and sIL-6R in acute and chronic rejection were higher than in the controls (P < 0.05). No differences in IL-6 levels were observed between the stable evolution and the control groups (P > 0.05). The levels of sIL-6R were higher in stable evolution patients than in the controls (P < 0.05) and no differences were observed between the chronic and stable evolution patients (P > 0.05). IL-6 decreased in patients with a favourable evolution, increased in those with an increased renal dysfunction and was maintained when the renal dysfunction was not modified. These results suggest that gammadelta T cells could participate in renal allograft maintenance and that IL-6 but not sIL-6R serum levels may provide a prognostic marker for measuring the evolution of kidney allograft.

Administration of an antigen at a high dose generates regulatory CD4+ T cells expressing CD95 ligand and secreting IL-4 in the liver

Ags administered orally at a high dose are absorbed in immunogenic forms and perfuse the liver, which raises a question regarding the relevance of hepatic lymphocyte activation to the systemic hyporesponsiveness against the ingested Ag. Oral administration of 100 mg of OVA to the mice led to massive cell death of OVA-specific (KJ1-26+)CD4+ T cells by Fas-Fas ligand (FasL)-mediated apoptosis in the liver, which was associated with the emergence of hepatic KJ1-26+CD4+ T cells expressing FasL. Hepatic CD4+ T cells in OVA-fed mice secreted large amounts of IL-4, IL-10, and TGF-beta(1) upon restimulation in vitro and inhibited T cell proliferation. Adoptive transfer of these hepatic CD4+ T cells to naive mice and subsequent antigenic challenge led to suppression of T cell proliferation as well as IgG Ab responses to OVA; this effect was mostly abrogated by a blocking Ab to FasL. i.p. administration of an Ag at a high dose also generated hepatic CD4+FasL+ T cells with similar cytokine profile as T cells activated by oral administration of Ags at a high dose. Finally, we did not see an increase in FasL+ cells in the hepatic CD4+Vbeta8+ T cell subset of MRL/lpr/lpr mice given staphylococcal enterotoxin B, indicating the requirement for Fas-mediated signals. These hepatic CD4+FasL+ regulatory cells may explain the tolerogenic property of the liver and play roles in systemic hyporesponsiveness induced by an Ag administered at a high dose.

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.

A novel strategy for organ allografts using sublethal (7 Gy) irradiation followed by injection of donor bone marrow cells via portal vein

A new strategy for organ allografts that does not require recourse to immunosuppressants is established in mice. The strategy includes sublethal (7 Gy) irradiation followed by the injection of donor bone marrow cells (BMCs) via the portal vein (P.V.) and organ allografts 1 day after irradiation. Irradiation doses (< or =7 Gy) are found to allow the recipients to survive without the need to reconstitute the BMCs, as the recipient hematolymphoid cells can gradually recover. One hundred percent of recipients irradiated with 7 Gy followed by either P.V. or i.v. injection of donor BMCs accept organ allografts (the skin, pancreas, and adrenal glands) for more than 1 year. However, organ allograft survival rates decrease when irradiation doses are reduced; the skin graft survival rate of mice treated with 6.5 Gy and P.V. injection of BMCs is 79%, whereas that of mice treated with 6.5 Gy and i.v. injection is 50%, indicating that the P.V. injection of BMCs induces persistent tolerance more effectively than the i.v. injection. H-2 typing reveals that almost all the hematolymphoid cells (>98%) in the peripheral blood and hematolymphoid organs are donor-derived even 1 year after the treatment (7 Gy and P.V.). The T cells are tolerant to both donor-type and host-type MHC determinants. The major mechanism underlying the persistent tolerance induced by this strategy seems to be because of clonal deletion. This simple and safe strategy would be of great advantage for human organ transplantation.

Induction of oral tolerance to cellular immune responses in the absence of Peyer's patches

Systemic hyporesponsiveness occurs following oral administration of antigen (oral tolerance) and involves the uptake and processing of antigen by the gut-associated lymphoid tissue (GALT), which includes Peyer's patches (PP) lamina propria lymphocytes and mesenteric lymph nodes (MLN). Animals with targeted mutations of genes in the tumor necrosis factor (TNF) family have differential defects in the development of peripheral lymphoid organs including PP and MLN, and provide a unique opportunity to investigate the role of GALT structures in the induction of oral tolerance. Oral tolerance could not be induced in TNF/lymphotoxin (LT) alpha-/- mice, which are devoid of both PP and MLN, although these animals could be tolerized by intraperitoneal administration of antigen, demonstrating the requirement for GALT for oral tolerance induction. LTbeta-/- mice and LTalpha/LTbeta+/- animals do not have PP but could be orally tolerized, as measured by IFN-gamma production and delayed-type hypersensitivity responses by administration of both low or high doses of ovalbumin. To further investigate the requirement for PP, we tested the progeny of LTbeta-receptor-IgG-fusion-protein (LTbetaRigG)-treated mice, which do not form PP but have an otherwise intact immune system. Although these animals had decreased fecal IgA production, they could be orally tolerized. Our results demonstrate that PP are not an absolute requirement for the induction of either high- or low-dose oral tolerance, although oral tolerance could not be induced in animals devoid of both PP and MLN.

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.

Detection of host and donor cells in sex-mismatched rat nerve allografts using RT-PCR for a Y chromosome (H-Y) marker

The donor and host source of support cells, such as Schwann cells, in nerve allograft segments have been the subject of debate. The objective of the present study was to assess the utility of a molecular technique that probes for a Y chromosome expressed gene (H-Y) in distinguishing host from donor tissue in sex-mismatched nerve allograft segments. Forty-two Lewis rats received bilateral syngeneic Lewis or allogeneic ACI rat peroneal nerve grafts, with or without cyclosporin A (CsA) treatment. At different times thereafter animals were sacrificed and samples were harvested. We transplanted males and females reciprocally, to study both survival of donor cells (persisting H-Y mRNA in male grafts by transcription polymerase chain reaction (RT-PCR), and graft infiltration by host cells (detectable H-Y mRNA in female grafts). A kinetic analysis revealed a progressive loss of viable donor cells (loss of H-Y mRNA signal) from allografts, beginning 2-3 weeks, and culminating at 4 weeks, with little detectable H-Y in the absence of CsA treatment. CsA treatment led to prolonged survival of allograft cells, confirmed by detectable H-Y mRNA. By studying female grafts in male rats we could confirm that loss of viable donor tissue in allografts was accompanied by infiltration of host (H-Y mRNA positive) cells, whereas no H-Y mRNA signal was seen in males receiving autografts from females or in immunosuppressed allograft segments. These data suggest that reverse RT-PCR analysis for a Y chromosome gene product can be a valuable tool to assess the origin of viable cells in sex-mismatched nerve allotransplantation tissue.

[gamma][delta] cells: a right time and a right place for a conserved third way of protection

The tripartite subdivision of lymphocytes into B cells, alphabeta T cells, and gammadelta cells has been conserved seemingly since the emergence of jawed vertebrates, more than 450 million years ago. Yet, while we understand much about B cells and alphabeta T cells, we lack a compelling explanation for the evolutionary conservation of gammadelta cells. Such an explanation may soon be forthcoming as advances in unraveling the biochemistry of gammadelta cell interactions are reconciled with the abnormal phenotypes of gammadelta-deficient mice and with the striking differences in gammadelta cell activities in different strains and species. In this review, the properties of gammadelta cells form a basis for understanding gammadelta cell interactions with antigens and other cells that in turn form a basis for understanding immunoprotective and regulatory functions of gammadelta cells in vivo. We conclude by considering which gammadelta cell functions may be most critical.

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.

Cutting Edge: Protective Response to Pulmonary Injury Requires γδ T Lymphocytes

γδ intraepithelial lymphocytes are thought to coordinate responses to pathogens that penetrate the epithelial barrier. To directly test this, mice were inoculated with Nocardia asteroides. At doses that were nonlethal for control mice, γδ-deficient mice became severely ill and died within 14 days. Histologic examination of these lungs demonstrated the presence of severe tissue damage and unimpeded bacterial growth in the γδ-deficient mice compared with neutrophilic lesions and clearance of the organism in control mice. Interestingly, ozone exposure that targets a comparable lung region also resulted in diffuse epithelial necrosis associated with a similar lack of neutrophil recruitment in γδ-deficient mice. These data demonstrate that γδ intraepithelial lymphocytes can protect the host from pathogenic and nonpathogenic insults by targeting the inflammatory response to epithelial necrosis.

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.

TCR diversity in gammadeltaTCR+ hybridomas derived from mice given portal vein donor-specific pre-immunization and skin allografts

Portal venous (p.v.) immunization with multiple minor histoincompatible cells leads to antigen-specific increased skin allograft survival. GammadeltaTCR+ hybridoma cells, prepared from mesenteric lymphocytes of p.v. immunized animals, can adoptively transfer this increased graft survival to naive animals. We have analyzed VgammaVdelta gene usage, and TCR gamma-chain junctional diversity in gammadeltaTCR+ hybridomas from mice immunized with different antigen combinations by p.v. or conventional lateral tail vein (i.v.) immunization. Following p.v. immunization two independent sets of hybridoma cells were derived, one expressing a common gamma-chain junctional sequence which was also found in > 85% of the hybridomas derived following i.v. immunization, while the other set showed remarkable gamma-chain junctional sequence diversity. The diversity seen in these latter hybridomas was associated with the antigen specificity of the hybridoma cells. Cells expressing these 'unique' TCR junctional sequences were stimulated to produce cytokines both by hsp and by minor-histocompatibility-specific irradiated peritoneal cells. Cells expressing TCR with a common gamma-chain junctional sequence were stimulated to cytokine production by MHC-matched but minor-histocompatibility mismatched (as well as matched) peritoneal cells, but not by hsp. We suggest that p.v. immunization results in stimulation of both antigen-specific and non-specific regulatory gammadeltaTCR+ cells, which can be distinguished by gamma-chain TCR sequence diversity.

Prolongation of survival of primary renal allografts by feeding of donor spleen cells

We have found that feeding Brown Norway (BN) rat spleen cells to Lewis rats prior to transplanting BN kidneys prolongs allograft survival (mean: 8.8 days in unfed rats, 21 days in the BN cell-fed rats; longest survival: 11 days without allo-feeding vs. 37 days with feeding). We have also found that feeding BN cells both before and after transplantation further extends survival (mean: 38 days; longest survival: 105 days). We also examined the cells infiltrating the grafts during the early stages of the allograft response (day 5). Using flow cytometry, we found a significant decrease in the number of leukocytes infiltrating the transplanted kidneys of fed animals. This decrease was mainly due to a drop in the number of infiltrating T cells. We also found that cytokine mRNA production by the graft-infiltrating lymphocytes, assessed by reverse transcription polymerase chain reaction, showed a significant increase in interleukin-4 and transforming-growth factor-beta mRNA in the graft-infiltrating lymphocytes of fed animals compared with the controls.

Activated sub-populations of lymphocytes and natural killer cells in normal liver and liver grafts before transplantation

AIMS/BACKGROUND

The anatomic structure of the liver suggests that it is a place of intense trafficking between intra-hepatic and peripheral blood compartment leukocytes. Furthermore, the liver contains a large number of passenger leukocytes that may play a role in the appearance of donor-type microchimerism after transplantation. In this study, we aimed to define the principal lymphocyte sub-populations contained in donor peripheral blood and liver grafts and in normal liver removed during minimally invasive surgery.

METHODS

Liver biopsies were taken at the time of vascular clampage during liver extraction from donors in a brain dead state (GI: n=14). Normal liver biopsies were removed during minimaly invasive surgery (GII: n= 10).

RESULTS

We observed evidence of the presence of lymphocytic activation associated with the two major CD8+ lymphocyte and natural killer (NK) cell populations in the two groups, with a significant increase in TCRgammadelta-bearing lymphocyte receptors between normal liver and the liver graft.

CONCLUSIONS

The presence of activated leukocytes in the graft could have a fundamental role in induction of peripheral tolerance. This activation could be the result of a basic immunological response linked to the interaction of T cells and NK cells, and of secondary activation due to stress and the conditions necessary for organ removal from donors in a brain dead state.

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.

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.

Portal venous transfusion up-regulates Kupffer cell cyclooxygenase activity: a mechanism of immunosuppression in organ transplantation

Portal venous transfusions (PVTs) of blood have been shown to induce significant immunosuppression in animal models of organ transplantation. A proposed mechanism of PVT-induced immunosuppression is via alteration of Kupffer cell arachidonic acid metabolism with increased secretion of the suppressive metabolite prostaglandin E2 (PGE2). This study assessed the hypothesis that PVT increases Kupffer cell PGE2 production via up-regulation of Kupffer cell phospholipase A2 (PLA2) as well as constitutive (COX1) and inducible (COX2) cyclooxygenase. Kupffer cells from Lewis rats were harvested 1 hr after PVT with either 1 ml of Wistar-Furth blood, systemic transfusion (SVT), or saline via portal vein (PVSal). After lipopolysaccharide stimulation, 24-hr Kupffer cell supernatant fractions were assayed for PGE2. PGE2 was increased after SVT (1465+/-234 pg/ml) compared with PVSal (597+/-99; P<0.01). PVT increased Kupffer cell PGE2 (5370+/-533; P<0.001 vs. SVT and vs. PVSal) even more substantially. Kupffer cells from PVT-treated rats were then cultured in the presence of inhibitors of PLA2, COX1, or COX2. When Kupffer cells were treated with mepacrine to inhibit PLA2 (5575+/-453 pg/ml), PGE2 production was not different from that by PVSal-treated controls (6467+/-614 pg/ml), but when Kupffer cells were incubated in the presence of the COX1 inhibitor flurbiprofen (3512+/-407 pg/ml) or the COX2 inhibitor nimesulide (2800+/-830 pg/ml), production was decreased 46.7% and 56.7%, respectively, over control activity without added inhibitor. PVT also increased Kupffer cells COX1 and COX2 mRNA as measured by Northern blot. Heart transplants were then performed from Wistar-Furth donors into Lewis recipients at the time of PVT, SVT, PVSal, or PVT + indomethacin (COX1/2 inhibitor). PVT prolonged allograft survival (12.0+/-0.9 days) compared with PVSal (6.3+/-0.3; P<0.01) or SVT (6.3+/-0.3; P<0.04). Indomethacin shortened graft survival when given with PVT (6.5+/-0.3 days). In summary, PVT increased Kupffer cell PGE2 production, up-regulated transcription of Kupffer cells COX1 and COX2 mRNA, and prolonged cardiac allograft survival. COX1/2 inhibition abrogated the effect of PVT. The results indicated that the immunosuppressive effect of PVT may be mediated by up-regulation of Kupffer cell COX1 and COX2. Manipulation of Kupffer cell arachidonic acid metabolism may be useful in augmentation of PVT-induced immunosuppression.

Interleukin-13, in combination with anti-interleukin-12, increases graft prolongation after portal venous immunization with cultured allogeneic bone marrow-derived dendritic cells

Portal venous (pv) transfusion before transplant with large numbers (100 x 10(6)) of irradiated multiple minor histoincompatible spleen cells (B10.Br) augments allogeneic skin graft survival in C3H mice. We have shown in earlier studies that this is correlated with preferential activation for production of type 2 cytokines (interleukin [IL]-4 and IL-10) and decreased production of type 1 cytokines (IL-2 and interferon [IFN] gamma). We have also shown that recombinant (r)IL-12, in association with anti-IL-10 monoclonal antibody, can reverse in vivo the graft prolongation afforded by pv immunization and the altered cytokine production that follows. Adoptive transfer of inhibition of graft rejection is possible at early times after pv immunization, using plastic adherent cells obtained from the liver of treated mice. We show below that within 4 days of pv immunization, dendritic cells (NLDC-145+) isolated from the thymus, mesenteric lymph node (MLN), and.

A role for gamma(delta)TCR+ cells in regulation of rejection of small intestinal allografts in rats

Lewis (LEW) rats received (Lewis x Brown Norway)F1 (LBNF1) small intestinal allografts (SIT) with graft venous drainage to either the portal vein (pv) or inferior vena cava (iv), along with immunization (pv or iv) with irradiated LBNF1 spleen cells. As reported earlier, in rats with pv drained grafts there was an increase in gammadeltaTCR+ cells infiltrating the Peyer's patches (PP) and mesenteric lymph node (MLN) compared with iv drained grafts. After restimulation in culture with irradiated LBNF1 spleen stimulator cells these PP and MLN cells from SIT rats with pv graft drainage were a prominent source of TGFbeta, IL-4, and IL-10. When subpopulations of cells from PP preparations were analyzed, an enriched (<2%betaTCR+) gammadeltaTCR+ population from SIT rats with pv graft drainage, but not iv drainage, was detected that suppressed in vitro type-1 cytokine production (IL-2, IFNgamma) from alphabetaTCR+ (<2%gammadeltaTCR+) cells derived from the MLN or peripheral lymph nodes (PLN) of these same animals. On adoptive transfer to naive LEW rats simultaneously receiving LBNF1 SIT, gammadeltaTCR+ enriched PP cells from these primary donors (pv immunized, SIT rats with pv graft drainage) produced prolonged graft/ animal survival compared with PP cells obtained from primary donors that had iv drained grafts. In addition, simultaneous infusion of anti-gammadeltaTCR monoclonal antibody into SIT rats with pv graft drainage blocked the graft enhancement normally seen in these animals. These data are consistent with an important role for type-2 cytokine producing gammadeltaTCR+ cells in the regulation of graft rejection in this model.