The protective effect of CD8+CD28- T suppressor cells on the acute rejection responses in rat liver transplantation. Transplant Proc. 2007;39:3396-3403. [PMID: 18089392 DOI: 10.1016/j.transproceed.2007.06.089]

Characteristics of changes in double positive CD4+CD8+ T cells in liver transplantation

Although double positive CD4⁺CD8⁺ T (DPT) cells has been reported to be involved in some diseases, their trajectory and function as associated with liver transplantation (LT) remain unclear. In the present study, we found that the number of DPT cells was increased in the blood and liver tissue of LT patients. Meanwhile, we compared the distribution of DPT cells in peripheral blood samples and in penetrating liver tissue between liver rejection versus non-rejection patients, as well as the proportion of DPT cells as a function of the extent of liver rejection. The number of DPT cells in the rejection group was significantly increased. An analysis of the spatial distance and correlations between DPT and Treg cells, revealed that these cells showed a high degree of contiguity. In a mouse liver transplant model, the number of DPT cells were significantly increased in liver tissue, and the number of CD8⁺ T cells gradually increased, while CD4⁺ T cells decreased as a function of time post-transplantation. Expression level of PD-1 in DPT cells also increased in a temporally-dependent manner post liver transplantation and the changes of PD-1⁺ DPT cells were related to the degree of liver transplant rejection. In DPT cells interacting with Treg, there was an increased expression of PD-1, which enhanced cellular exhaustion. In conclusion, the capacity for DPT cells to induce immune tolerance may represent a new and important protocol for use in targeting treatments for the prevention of liver transplant rejection.

Th2 cells lacking T-bet suppress naive and memory T cell responses via IL-10

Exacerbated immune responses and loss of self-tolerance lead to the development of autoimmunity and immunopathology. Novel therapies to target autoreactive T cells are still needed. Here, we report that Th2-polarized T cells lacking the transcription factor T-bet harbor strong immunomodulatory potential and suppress antigen-specific CD8+ T cells via IL-10. Tbx21-/- Th2 cells protected mice against virus-induced type 1 diabetes development and suppressed not only naive but also memory CD8+ T cell responses. IL-10-producing, but not IL-10-deficient Tbx21-/- Th2 cells down-regulated costimulatory molecules on dendritic cells and reduced their IL-12 production after lymphocytic choriomeningitis virus infection. Impaired dendritic cell activation hindered effector and cytotoxic CD8+ T cell development after infection. These findings indicate that Tbx21-/- Th2 cells strongly suppress proinflammatory responses of naive and memory T cells via IL-10. Thus, in vivo IL-10-secreting Th2 cells could harbor a therapeutic potential for the treatment of T cell-mediated inflammatory disorders.

Prolongation of rat-to-mouse islets xenograft survival by co-transplantation of autologous IL-10 differentiated murine tolerogenic dendritic cells

BACKGROUND

Tolerogenic dendritic cells (DCs) represent a promising approach to promote transplantation tolerance. In this study, the potential of autologous bone marrow (BM)-derived murine DC to protect rat-to-mouse islets xenografts was analyzed.

METHODS

Tolerogenic DCs were generated by differentiating BM cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin 10 (IL-10, IL-10 DC). The phenotype of IL-10 DC was characterized in vitro by expression of costimulatory/inhibitory molecules (flow cytometry) and cytokines (Luminex and ELISA), their function by phagocytosis and T-cell stimulation assays. To study transplant tolerance in vivo, rat islets were transplanted alone or in combination with autologous murine IL-10 DC under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. Xenograft survival was evaluated by monitoring glycemia, cellular infiltration of xenografts by microscopy and flow cytometry 10 days post-transplantation.

RESULTS

Compared with control DC, IL-10 DC exhibited lower levels of major histocompatibility complex class II, costimulatory molecules (CD40, CD86, CD205), lower production of pro-inflammatory cytokines (IL-12p70, TNF, IL-6), and higher production of IL-10. Phagocytosis of xenogeneic rat splenocytes was not impaired in IL-10 DC, whereas stimulation of T-cell proliferation was reduced in the presence of IL-10 DC. Xenograft survival of rat islets in diabetic mice co-transplanted with autologous murine IL-10 DC was significantly prolonged from 12 to 21 days, without additional immunosuppressive treatment. Overall, infiltration of xenografts by T cells and myeloid cells was not different in IL-10 DC recipient mice, but enriched for CD8⁺ T cells and myeloid cells with suppressor-associated phenotype.

CONCLUSIONS

Autologous IL-10-differentiated DC with tolerogenic properties prolong rat-to-mouse islets xenograft survival, potentially by locally inducing immune regulatory cells, indicating their potential for regulatory immune cell therapy in xenotransplantation.

Targeting CD8 T-Cell Metabolism in Transplantation

Infiltration of effector CD8 T cells plays a major role in allograft rejection, and increases in memory and terminally differentiated effector memory CD8 T cells are associated with long-term allograft dysfunction. Alternatively, CD8 regulatory T cells suppress the inflammatory responses of effector lymphocytes and induce allograft tolerance in animal models. Recently, there has been a renewed interest in the field of immunometabolics and its important role in CD8 function and differentiation. The purpose of this review is to highlight the key metabolic pathways involved in CD8 T cells and to discuss how manipulating these metabolic pathways could lead to new immunosuppressive strategies for the transplantation field.

Role of CD8(+) regulatory T cells in organ transplantation

CD8⁺ T cells are regulatory T cells (Tregs) that suppress both alloimmunity and autoimmunity in many animal models. This class of regulatory cells includes the CD8⁺CD28⁻, CD8⁺CD103⁺, CD8⁺FoxP3⁺ and CD8⁺CD122⁺ subsets. The mechanisms of action of these regulatory cells are not fully understood; however, the secretion of immunosuppressive cytokines, such as interleukin (IL)-4, IL-10 and transforming growth factor beta (TGF-β) as well as the direct killing of target cells via Fas L/Fas and the perforin/granzyme B pathways have been demonstrated in various models. Further studies are necessary to fully understand the mechanisms underlying the suppressive effects of Tregs and to provide experimental support for potential clinical trials. We recently observed that CD8⁺CD122⁺ Tregs more potently suppressed allograft rejection compared to their CD4⁺CD25⁺ counterparts, supporting the hypothesis that CD8⁺ Tregs may represent a new and promising Treg family that can be targeted to prevent allograft rejection in the clinic. In this review, we summarize the progress in the field during the past 7–10 years and discuss CD8⁺ Treg phenotypes, mechanisms of action, and their potential clinical applications; particularly in composite tissue transplants in burn and trauma patients.

Donor dendritic cell proliferation and migration in hepatic allografts by pretransplant intraportal infusion of recipient blood into donor rats

INTRODUCTION

We have reported that recipient blood transfusion pretransplant prolongs hepatic allograft survival in rats. This study further investigated the mechanisms of the phenomenon.

MATERIALS AND METHODS

Male LEW and ACI rats were used as liver transplant recipients and donors, respectively. Experimental animals were divided into control; treatment experimental; and intraportally transfused (1 mL recipient blood) at 7 days before transplantation.

RESULTS

Rat survival time was significantly longer among the experiment versus the control group. A large number of donor-source dendritic cells were detected among infiltrating cells in the liver and spleen in the experimental group.

CONCLUSION

We concluded that the prolonged survival of hepatic allograft in these rats was associated with donor dendritic cell proliferation and migration.

High incidence of biliary complications in rat liver transplantation: Can we avoid it?

AIM: To investigate how to reduce the incidence of biliary complications in rat orthotopic liver transplantation.

METHODS: A total of 165 male Wistar rats were randomly divided into three groups: Group A, orthotropic liver transplantation with modified “two-cuff” technique; Group B, bile duct was cut and reconstructed without transplantation; and Group C, only laparotomy was performed. Based on the approaches used for biliary reconstruction, Group A was divided into two sub-groups:A1 (n = 30), duct-duct reconstruction, and A2 (n = 30), duct-duodenum reconstruction. To study the influence of artery reconstruction on bile duct complication, Group B was divided into four sub-groups: B1 (n = 10), duct-duct reconstruction with hepatic artery ligation, B2 (n = 10), duct-duct reconstruction without hepatic artery ligation, B3 (n = 10), duct-duodenum reconstruction with hepatic artery ligation, and B4 (n = 10), duct-duodenum reconstruction without hepatic artery ligation. The samples were harvested 14 d after operation or at the time when significant biliary complication was found.

RESULTS: In Group A, the anhepatic phase was 13.7 ± 1.06 min, and cold ischemia time was 50.5 ± 8.6 min. There was no significant difference between A1 and A2 in the operation duration. The time for biliary reconstruction was almost the same among all groups. The success rate for transplantation was 98.3% (59/60). Significant differences were found in the incidence of biliary complications in Groups A (41.7%), B (27.5%) and C (0%). A2 was more likely to have biliary complications than A1 (50% vs 33.3%). B3 had the highest incidence of biliary complications in Group B.

CONCLUSION: Biliary complications are almost inevitable using the classical “two cuff” techniques, and duct-duodenum reconstruction is not an ideal option in rat orthotopic liver transplantation.

Phenotypic and functional characterization of CD8(+) T regulatory cells

Increasing evidence shows the presence and significance of CD8+ T regulatory cells (CD8+ Tregs) in both human and rodent transplant recipients, as well as in autoimmune disease models. We, hereafter, review all available data on the phenotypic and functional characterization of CD8+ Tregs, and we also provide detailed protocols to purify them and analyze their suppressive function. Different subsets of dendritic cells (DCs) and CD4+ effector T cells may modulate the suppression mediated by CD8+ Tregs. By analyzing the proliferation of CFSE-labeled naïve CD4+CD25- T cells in coculture MLR and transwell experiments, we explored the mutual modulation of CD8+ Tregs, DC subsets, and CD4+ T effector cells. The suppressive function of CD8+ Tregs was mediated by both cell-contact-dependent and -independent mechanisms.

Regulatory T Cells in children with intestinal parasite infection

Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4(+) CD25(high) and CD4(+) Foxp3(+) cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3(+) CD69(+), CD4(+) CTLA-4(+), and CD8(+) CD28(-) T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3(+) CD69(+), CD4(+) CTLA-4(+) and CD8(+) CD28(-) lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children.

Effects of simvastatin on circulating autoantibodies to oxidized LDL antigens: relation with immune stimulation markers

Statins exert a number of anti-inflammatory and immunomodulatory effects in vitro. However, the immunomodulatory effects in vivo are less clarified. In the present study, we investigated whether simvastatin treatment changed the levels of autoantibodies against specific oxidized LDL (oxLDL) antigens as well as their association with leukocyte activation markers. Eighty volunteers with mild-to-moderate hypercholesterolemia were randomized to either simvastatin 40 mg or placebo for 6 weeks. Autoantibodies against apo B peptide antigens, C-reactive protein (CRP) and interleukin (IL)-6 in plasma were determined by ELISA. Subsets of circulating B and T cells were studied by flow cytometry. Simvastatin significantly reduced CRP by 26%, whereas IL-6 remained unchanged. Levels of IgG against the apo B peptide P-240 (amino acids 3586-3605) increased by 16% (p = 0.03) in the simvastatin group whereas autoantibody levels to other apo B peptides did not change. At baseline and after 6 weeks, the P-240 IgG levels were significantly correlated with the number of CD57+CD28 - CD8+T cells but not to other lymphocyte subsets or inflammatory markers. The P-240 IgG levels after 6 weeks simvastatin therapy was strongly correlated to the relative increase in CD57+CD28 - CD8+T cells (p = 0.003). Simvastatin treatment induced an increase in autoantibodies against an oxLDL antigen. The effect was related to an expansion of a CD8+T cell subset and may involve an immunostimulation by simvastatin.

Effects of omega-3 fatty acid transfusion on acute rejection in rat liver transplantation

AIM: To discuss the effect of omega-3 fatty acid on liver function, receiver's immunologic function and acute rejection following orthotopic liver transplantation in rats.

METHODS: Orthotopic liver transplantation using two-cuff technique from BN (RT1n) to Lewis (RT1l) was performed in 18 rats. After transplantation, the internal jugular vein tube was catheterized and the solution was given through a micro-pump. Normal saline was given to the NS group (n = 6), parenteral nutrition to PN group (n = 6), and parenteral nutrition + Omega-3 fatty acid to OM group (n = 6). At 7th day, the liver function, levels of cytokines (IL-2, IL-4, IL-10, γ-IFN) and pathological changes of the liver were observed. The percentage of CD4⁺, CD8⁺, CD4⁺CD25⁺ and CD8⁺CD28^- T lymphocytes were analyzed using flow-cytometry.

RESULTS: There were no significant differences among NS, PN and OM groups in liver function. In OM group, the CD4⁺, CD8⁺, CD4⁺CD25⁺ and CD8⁺CD28^- T lymphocytes were significantly decreased, compared with NS group and PN group (26.86% ± 1.60% vs 31.32% ± 5.92%, 32.87% ± 2.744%; 28.65% ± 1.40% vs 30.08% ± 1.37%, 30.64% ± 1.47%; 3.89% ± 0.20% vs4.75% ± 0.46%, 5.27% ± 0.20%; 13.31% ± 2.06% vs 22.08% ± 3.81%, 21.00% ± 3.46%, all P < 0.05). The ratio of CD4⁺/CD8⁺ of OM group was significantly decreased, compared with the other two groups (0.94 ± 0.001 vs 1.04 ± 0.01, 1.07 ± 0.001, P < 0.05). The levels of IL-2 and γ-IFN of OM group were significantly elevated, compared with NS group and PN group (20.17 ± 2.87 ng/L vs 35.47 ± 8.94 ng/L, 35.92 ± 3.31 g/L, 2.12 ± 0.84 ng/L vs 28.30 ± 6.25 ng/L, 28.38 ± 11.07 ng/L, all P < 0.05). The pathology examination showed that the rejection activity index (RAI) of OM group were significantly decreased, compared with PN group or NS group (P < 0.05).

CONCLUSION: Omega-3 fatty acid decreases the secretion of IL-2 and γ-IFN, inhibits the T lymphocytes, especially the help T lymphocytes, and alleviates the acute rejection.

CD8(+)CD103(+) regulatory T cells in spontaneous tolerance of liver allografts

It has been shown that rat liver allografts between certain inbred major histocompatibility complex (MHC) disparate strains are accepted spontaneously, and regulatory T cells (Tregs) have been suggested to play a role in the spontaneous liver tolerance. CD8(+)CD103(+) T cells bear the phenotypes of effector cells, and they are implicated in allograft destruction. Here we provide evidence that CD8(+)CD103(+) T cells possess regulatory function and may contribute to prevent liver allograft rejection. We show that the expression of CD103 in the CD8(+) T cells was increased in spontaneous liver grafts tolerant recipients. We further show that CD8(+)CD103(-) T cells can also upregulate the expression of CD103 and Foxp3 after stimulation with alloantigen or TGF-beta in vitro, and the CD8(+)CD103(+) T cells acquired regulatory properties. The suppressive function of the alloantigen or TGF-beta conditioned CD8(+)CD103(+) T cells was cell-cell contact dependent. These results imply that liver-specific factor(s) would be involved in the generation of CD8(+)CD103(+) Tregs that contribute to spontaneous liver allografts tolerance.