Cold Ischemia Does Not Interfere With Tolerance Induction

Effect of Conversion to CTLA4Ig on Tacrolimus-Induced Diabetic Rats

BACKGROUND

The effect of conversion to cytotoxic T lymphocyte-associated protein 4 immunoglobulin (CTLA4Ig) treatment on tacrolimus (TAC)-induced renal dysfunction is well known, but its effect on TAC-induced diabetes mellitus (DM) is still undetermined. In the present study, we tested the diabetogenicity of CTLA4Ig and evaluated the effect of conversion to CTLA4Ig treatment on TAC-induced diabetic rats.

METHODS

We tested diabetogenicity of CTLA4Ig by escalating doses (0.25, 0.5, 1, 2, and 4 mg/kg weekly) for 4 weeks. In the conversion study, we administered TAC (1.5 mg/kg) for 3 weeks and confirmed TAC-induced DM by intraperitoneal glucose tolerance test. Thereafter, TAC administration was continued, withdrawn, or replaced by CTLA4Ig treatment (1 or 2 mg/kg) for additional 3 weeks. The effect of CTLA4Ig on TAC-induced DM in vivo and in vitro was evaluated by assessing pancreatic islet function, histopathology, oxidative stress, apoptosis, and macrophage infiltration.

RESULTS

Intraperitoneal glucose tolerance test in the CTLA4Ig groups did not differ from the control group. In addition, plasma insulin level, glucose-induced insulin secretion, and islet viability were not different between the CTLA4Ig and control groups. In the conversion study, TAC withdrawal ameliorated pancreatic islet dysfunction compared with the TAC group, and conversion to CTLA4Ig further improved pancreatic islet function compared with the TAC withdrawal group. TAC-induced oxidative stress, apoptotic cell death, and infiltration of macrophages decreased with TAC withdrawal, and CTLA4Ig conversion further reduced those values. In the in vitro study, CTLA4Ig decreased TAC-induced pancreatic islet cell death and reactive oxygen species production.

CONCLUSIONS

CTLA4Ig was not diabetogenic, and conversion to CTLA4Ig reduced TAC-induced pancreatic islet injury.

The effects of brain death and ischemia on tolerance induction are organ-specific

We have previously shown that 12 days of high-dose calcineurin inhibition induced tolerance in MHC inbred miniature swine receiving MHC-mismatched lung, kidney, or co-transplanted heart/kidney allografts. However, if lung grafts were procured from donation after brain death (DBD), and transplanted alone, they were rejected within 19-45 days. Here, we investigated whether donor brain death with or without allograft ischemia would also prevent tolerance induction in kidney or heart/kidney recipients. Four kidney recipients treated with 12 days of calcineurin inhibition received organs from donors rendered brain dead for 4 hours. Six heart/kidney recipients also treated with calcineurin inhibition received organs from donors rendered brain dead for 4 hours, 8 hours, or 4 hours with 4 additional hours of cold storage. In contrast to lung allograft recipients, all isolated kidney or heart/kidney recipients that received organs from DBD donors achieved long-term survival (>100 days) without histologic evidence of rejection. Proinflammatory cytokine gene expression was upregulated in lungs and hearts, but not kidney allografts, after brain death. These data suggest that the deleterious effects of brain death and ischemia on tolerance induction are organ-specific, which has implications for the application of tolerance to clinical transplantation.

Short-term TNF-alpha inhibition reduces short-term and long-term inflammatory changes post-ischemia/reperfusion in rat intestinal transplantation

BACKGROUND

Tumor necrosis factor (TNF)-α inhibition was shown to reduce ischemia/reperfusion injury (IRI) after intestinal transplantation (ITX). We studied the effects of different TNFα inhibitors on acute IRI and long-term inflammatory responses in experimental ITX.

METHODS

Orthotopic ITX was performed in an isogenic ischemia/reperfusion model in Lewis rats. The TNFα inhibition groups received infliximab post-reperfusion; etanercept pre-reperfusion and at postoperative days (POD) 1, 3, 5, and 7; or pentoxifylline pre-reperfusion and at POD 1 to 5. Tissue samples were taken from proximal and distal graft sections and mesenteric lymph nodes at 20 min, 12 hr, 7 day, and 6 months post-reperfusion for histopathology, immunohistology, terminal deoxyribosyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and real-time RT-PCR. Lung sections were stained for the myeloperoxidase assay.

RESULTS

TNFα inhibitors decreased inflammatory changes after IRI in all treatment groups. Infliximab significantly improved 7-day survival and reduced the histological and immunohistochemical signs of IRI, the numbers of graft-infiltrating T cells and ED1 monocytes and macrophages, and pulmonary neutrophil infiltration, and also enhanced the accumulation of cytoprotective markers. Graft injury was more prominent in the distal graft than in the proximal graft in all groups, regardless of TNFα inhibition.

CONCLUSION

Infliximab significantly reduced both acute IRI and, as with other TNFα inhibitors, long-term inflammatory responses after rat ITX. TNFα inhibition may help diminish chronic inflammatory long-term effects and avoid chronic allograft enteropathy.

Clinical relevance of the de novo production of anti-HLA antibodies following intestinal and multivisceral transplantation

Despite a negative pretransplant cross-match, intestinal transplant recipients can mount humoral immune responses soon after transplantation. Moreover, the development of donor-specific anti-HLA antibodies (DSAs) is associated with severe graft injury. Between June 2000 and August 2011, 30 patients (median age 37.6±9.8 years) received isolated intestinal transplantations (ITX, n=18) or multivisceral transplantations (MVTXs, n=12) at our center. We screened for human leukocyte antigen (HLA) antibodies pre- and post-transplant. If patients produced DSAs, treatment with plasmapheresis and intravenous immunoglobulin (IVIG) was initiated. In the event of DSA persistence and/or treatment-refractory rejection, rituximab and/or bortezomib were added. Ten patients developed DSAs and simultaneously showed significant signs of rejection. These patients received plasmapheresis and IVIG. Eight patients additionally received rituximab, and two patients were treated with bortezomib. DSA values decreased upon antirejection therapy in 8 of the 10 patients. The development of DSAs following ITX is often associated with acute rejection. We observed that the number of mismatched antigens and epitopes correlates with the probability of developing de novo DSAs. Early diagnosis and therapy, including B-cell depletion and plasma cell inhibition, are crucial to preventing further graft injury.

Prolonged cold ischemic time results in increased acute rejection in a rat allotransplantation model

BACKGROUND

The cold ischemic time may be more prolonged for facial tissue allografts than for organ allografts. Previous researches have shown that prolonged ischemia resulted in increased signs of rejection in a rat groin allotransplantation model; however, the relationship between cold ischemia and alloantigen-induced rejection was unclear.

MATERIALS AND METHODS

Vascularized groin flaps were transplanted from BN to Lewis rats after 0, 6, 12, 18, or 24 h of storage at 4 °C, and the allografts in each group were evaluated daily. Biopsy samples taken from the allo-0 h and allo-24 h groups on postoperative d 2-8 were graded for signs of acute rejection. Biopsy samples taken from the allo-0 h and allo-24 h groups on postoperative d 5 were stained for chemokine receptor CXCR3.

RESULTS

When the cold ischemia time was greater than 18 h, the survival time of the grafts was significantly shorter (6.2 ± 1.3 d) than that of the grafts that did not undergo cold ischemia (9.0 ± 1.2 d). Histological valuation showed acceleration of activated lymphocyte infiltration in the allo-24 h group (2.2 ± 0.4 d) compared with the allo-0 h group (4.8 ± 0.4 d). Furthermore, the proportion of CXCR3-positive cells in the allo-24 h group (49.7% ± 6.0%) was significantly higher than that in the allo-0 h group (22.9% ± 3.4%) on d 5 after transplantation.

CONCLUSIONS

Prolonged ischemia has a deleterious effect on allograft survival, and the chemokine receptor CXCR3 may play a role in this process.

Immunosuppression in high-risk transplantation

PURPOSE OF REVIEW

Increasingly, transplant clinicians are faced with providing candidates with increased risks for poorer outcome with donor grafts that also carry higher risks of failure. Understanding the role of immunosuppressive management in these combinations of higher risks remains important for optimizing results.

RECENT FINDINGS

Few immunosuppressive protocols have been rigorously tested in the high-risk renal transplant setting. The two main risk categories accounted for in the trials are those ones that confer increased risks to renal function, usually carried by the donor organs, and those protocols defined by increased risk for immunological failure, mostly determined by recipient characteristics. The studied protocols generally involve reduction or avoidance of nephrotoxic drugs in the first case and use of lymphocyte-depleting agents in the case of increased immunological risk. In both scenarios, acceptable short-term results have been achieved. However, long-term results for high-risk transplants defined either by donor or recipient factors have yet to be reported.

SUMMARY

The lack of long-term data for optimizing the right immunosuppressive regimen for a given donor/recipient risk profile remains an ongoing challenge for researchers and clinicians alike.