Tolerance induction permits the development of graft-versus-host disease: donor-mediated attack following small bowel transplantation in mixed chimeras

Prolonged survival of experimental extremity allografts: a new protocol with total body irradiation, granulocyte-colony stimulation factor, and FK506

The induction of a high-level of chimerism (macrochimerism) may be the most reliable strategy for achieving donor-specific tolerance. The purpose of this study was to evaluate the efficacy of a new protocol using total-body irradiation (TBI) and granulocyte-colony stimulation factor (G-CSF) to induce high-level chimerism following rat whole-limb allotransplantation. In this study, we investigated whether the timing of TBI influenced the period of graft survival. In total, 50 whole-limb allotransplants from LacZ transgenic rats to LEW rats were performed. TBI was performed at days 0 and 14, and G-CSF was given for 4 days after TBI. FK506 was given for 28 days after transplant. Nontreated limb allografts were rejected after 4.2 days. The survival time was prolonged to 64 days in the FK506 monotherapy group. In the group receiving TBI at day 14, limb allograft survival was significantly prolonged to 81 days. In the group receiving TBI at day 0, 26% of recipients died but in the surviving recipients the grafts survived for longer than 1 year without lethal graft-versus-host disease (GVHD). Polymerase chain reaction (PCR) analysis revealed a high level of intrabone marrow chimerism in the recipient, thus demonstrating successful induction of macrochimerism. A new protocol of pretransplant TBI followed by treatment with G-CSF and FK506 was found to induce a high level of chimerism and to significantly prolong the survival of limb allografts in recipients without lethal GVHD.

Immune tolerance in orthotopic liver transplantation induced by allogenic bone marrow transplantation in rats

AIM: To establish the allogeneic animal bone marrow and orthotopic liver transplantation model in rats, and to investigate the feasibility and possible mechanism of immune tolerance induced by allogeneic animal bone marrow tansplantation.

METHODS: SD rats (donor, ♂) and Wistar rats (recipient, ♀) were randomly and averagely divided into three groups and conditioned by three methods. Group II Wistar rats (recipient, ♀) were induced with sublethal total body irradiation (TBI, 11 Gy) and group III with TBI (7 Gy), followed by infusion of SD (donor, ♂) rat bone marrow cells (8×10⁷) within 4 h, then rats in group III were administered intraperitoneally with cytoxan (CTX, 50 mg/kg) 2 days later. Then three groups were performed orthotopic liver transplantations using modified Kamada's two-cuff technique in rats 28 days later. According to the GenBank, the specific primer of rat SRY gene was designed. Recipient rats were detected for donor origin cells in the peripheral blood lymphocyte on day 10, 20 using polymerase chain reaction (PCR). PCR product was analyzed by electrophoresis. Delayed type hypersensitivity (DTH), survival time and the histopathologic changes in liver after liver transplantation in rats were compared.

RESULTS: Chimera of SD rats was found in the peripheral blood lymphocytes of the Wistar rats in Group II and III. DTH results showed that Wistar rats were specifically tolerant to the SD rats. The DTH in group II or III is obviously lower than that in group I (0.22 ± 0.028 mm, 0.23 ± 0.032 mm vs 0.71 ± 0.026 mm, P < 0.01). The rats in Group I died 4-5 days later. The survival rate in Group II or III were significantly higher than that in group I (8.14 ± 2.53 d, 8.33 ± 2.11 d vs 3.79 ±0.83 d, P < 0.01). According the Banff scores, the rats in group II and III showed lighter pathological changes than in group I.

CONCLUSION: Treatment of 7 Gy TBI and the injection of CTX (50 mg/kg) plus donor bone marrow transplantation (BMT) establishes a rat chimera model successfully and enhance the survival time of liver transplantation model in rats. Infusion of the bone marrow cells might be an effective method for maintaining the tolerant state and for prolonging survival time of liver transplantation model in rats.

Regulation of Donor T Cells in the Tolerant Rats to Graft-Versus-Host Disease by FTY720 Following Small Bowel Transplantation

AIMS

The potency of immunosuppression is a critical factor in small bowel transplantation (SBTx). FTY720 altered lymphocyte trafficking and prevented the donor T cells from migrating into target organs, resulting in the prolongation of recipient survival in acute graft-versus-host disease (GVHD) of SBTx. However, the effect of FTY720 on donor T cells in the chronic phase of GVHD following SBTx remains unclear.

METHODS

Heterotopic SBTx was performed in a WF-to-F1 (WF x ACI) rat combination. Recipients were given FTY720 for 14 days after SBTx. The subpopulations of donor-derived T cells and the cytokine production in the target tissues were evaluated on postoperative day 150.

RESULTS

FTY720 treatment significantly prolonged recipient survival over 150 days without any clinical signs of GVHD. The numbers of donor-derived CD4+ and CD8+ T cells in the peripheral blood, mesenteric lymph nodes, and Peyer's patches of recipients were maintained at low levels on postoperative 150, which were almost similar to the levels on postoperative day 14. In the host lamina propria, however, a significant higher number of donor T cells (CD4+, 18.4 +/- 4.3 x 10(4); CD8+, 13.9 +/- 3.6 x 10(4)) were still observed on postoperative day 150. Production of interferon-gamma was significantly reduced in target tissues by FTY720 treatment both in the acute and chronic phase. However, interleukin-4 and interleukin-10 production, which was significantly higher on day 14, returned to the level of naive rats in the chronic phase.

CONCLUSIONS

A 14-day treatment of FTY720 induced tolerance in our SBTx model. Down-regulation of both Th1 and Th2 immune response was observed in the chronic phase.

Intestinal graft versus native liver cytokine expression in a rat model of intestinal transplantation with and without donor-specific cell augmentation

BACKGROUND

Immunomodulatory strategies such as donor-specific bone marrow or blood transfusions have been used to promote engraftment after intestinal transplants. We previously showed that delivery of donor antigen via the portal vein can effectively reduce the rate of intestinal graft rejection. The purpose of our current study was to investigate the impact of donor-specific cell augmentation (blood versus bone marrow) via the portal vein on cytokine expression in intestinal grafts versus native livers.

MATERIAL AND METHODS

We performed heterotopic small intestinal transplants between male Brown-Norway (donor) and female Lewis (recipient) rats. We studied 10 groups according to the type of donor-specific cell augmentation and the use and dose of immunosuppressive therapy. For cell augmentation, donor-specific blood or bone marrow was transfused via the donor portal vein immediately before graft implantation. For immunosuppression, tacrolimus was used post-transplant at a high or low dose. Control rats received neither immunosuppression nor cell augmentation. Tissue samples for histological assessment were obtained at designated time points. RNA was extracted from intestinal graft and native liver biopsies for cytokine measurements (IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IFN-gamma, TNF-alpha, and TNF-beta). Chimerism levels were determined using Q-PCR analysis.

RESULTS

Without concurrent immunosuppression, neither portal donor-specific blood nor bone marrow transfusion reduced the rate of rejection. With immunosuppression, outcome was significantly better after portal donor-specific blood (versus bone marrow) transfusion. Irrespective of the type of donor-specific cell augmentation, severe rejection caused strong cytokine expression in the grafts of IL-1 alpha, IL-1 beta, IFN-gamma, and TNF-alpha; in the native livers, mainly of TNF-alpha (with IFN-gamma showing hardly any increase). In general, rejection caused stronger cytokine expression in the grafts than in the native livers. Mild rejection correlated well with strong intragraft expression of IL-6, TNF-alpha, and TNF-beta (early rejection markers); severe rejection with IL-1 alpha, IL-1 beta, IFN-gamma, and TNF-alpha (late rejection markers). In addition to cell augmentation per se, the type of cell augmentation also had an impact on cytokine expression in both grafts and native livers. Cell-augmented (versus tacrolimus-treated) rats showed hardly any differences in intragraft cytokine expression, but the expression of almost all cytokines was significantly stronger in the native livers. With immunosuppression, bone marrow infusion increased intragraft cytokine expression of IL-1 alpha, IL-1 beta, IFN-gamma, and TNF alpha, as well as liver cytokine expression of IL-1 beta, compared to blood transfusion. This finding reflected the more advanced rejection stages in the bone marrow infused group; different types of donor-specific cell augmentation had similar effects on liver cytokine expression. In the absence of myoablative therapy, chimerism levels were low, in both cell-augmented and non-cell-augmented groups.

CONCLUSIONS

Rejection and donor-specific cell augmentation independently causes differences in intragraft versus native liver cytokine expression after intestinal transplants. Portal donor-specific blood transfusion, as compared with donor-specific bone marrow infusion, lowered the incidence of rejection and diminished intragraft cytokine up-regulation.

Composite tissue allotransplantation in chimeric hosts: part I. Prevention of graft-versus-host disease

BACKGROUND

Mixed allogeneic chimerism (MAC) has been shown to induce tolerance to composite tissue allografts (CTA). However, transplantation of unmanipulated donor-specific limbs results in severe graft-versus-host disease (GVHD). This suggests that nontolerant mature donor-derived cells in the CTA may affect the stability of chimerism, potentially resulting in GVHD. The aim of this study was to develop an approach to study and prevent GVHD in a mixed chimeric-rat hind-limb transplantation model.

METHODS

[ACI-->WF] chimeras received a limb from Wistar Furth (WF) (syngeneic), Fisher (third-party), or ACI (irradiated [1,050 cGy] or nonirradiated) rats. In vitro tolerance was assessed using mixed lymphocyte reactivity (MLR) assays at the time the animals were killed.

RESULTS

[ACI-->WF] chimeras with greater than 85% chimerism exhibited rejection-free survival of donor-specific hind limbs. However, 100% of these animals developed lethal GVHD 22.4+/-2.8 days after limb transplantation. [ACI-->WF] chimeras that underwent transplantation with irradiated ACI or syngeneic WF limbs showed no signs of rejection or GVHD at 5 months. Nonchimeric and third-party controls rejected limbs within 10 days.

CONCLUSIONS

Conditioning of the host WF rats with 950 cGy of irradiation (sublethal, myeloablative) led to high levels of MAC without GVHD. The mature T-cell content of nonirradiated donor (ACI) limbs was sufficient to induce lethal GVHD in 100% of tolerant mixed chimeric [ACI-->WF] hosts. Irradiation of donor limbs before transplantation resulted in long-term donor-specific tolerance and prevented GVHD. These data demonstrate that (1) established chimeras could be susceptible to GVHD caused by immunocompetent donor cells transferred with the hind limb, and (2) inactivating these cells with irradiation prevents GVHD and destabilization of chimerism, and permits rejection-free graft acceptance.