The effects of tolerance on allograft damage caused by the innate immune system.

BACKGROUND: It is not known whether tolerance can be induced in a strong proinflammatory milieu or whether the induction of tolerance can prevent interferon (IFN)-gamma-associated graft injury. To address these questions, we studied the effects of rIFN-gamma infusion on porcine cardiac allograft survival. METHODS: Recombinant interferon (rIFN)-gamma was continuously infused into the left anterior descending artery of hearts transplanted into major histocompatibility complex-inbred miniature swine treated with a 12-day course of cyclosporine A. Group 1 recipients received a nearly syngeneic heart, group 2 recipients received a class I disparate heart, and group 3 recipients were cotransplanted with a class I-disparate heart and kidney, a procedure demonstrated to induce tolerance to both grafts. A fourth group of animals were not transplanted but received intracoronary rIFN-gamma infusion into the native heart. RESULTS: rIFN-gamma perfusion not only accelerated the acute rejection of class I-disparate hearts (mean survival time, 19+/-7.21 vs. 38+/-8.19; P=0.025) but caused near-syngeneic heart transplants, which otherwise survived indefinitely, to reject within 35 days. In contrast, rIFN-gamma perfusion had no demonstrable effects on hearts grafts in tolerant recipients or on autologous hearts. CONCLUSIONS: These results suggest that tolerance induction can occur in the presence of IFN-gamma-mediated inflammation, and that tolerance induction can prevent the tissue injury caused by the overproduction of IFN-gamma. This suggests that the beneficial effects of tolerance may include protection from nonspecific inflammatory responses, such as those produced by ischemia-reperfusion injury and brain death.

Derotation of post-traumatic femoral deformities by closed intramedullary sawing.

Different techniques and devices have been used for correction osteotomies of bones in patients with malalignments. The most frequently used technique for rotational deformities of the femur and tibia is open osteotomy with an oscillating saw and pre-drilled holes with all well-known drawbacks of open surgery. An intramedullary device with an adapted minimal-invasive surgical technique allows intramedullary osteotomy of the bone preserving the surrounding soft tissue. We performed femoral osteotomies with an intramedullary saw followed by static interlocking nailing in 14 patients with post-traumatic rotational deformity in the femur. Twelve patients had an external rotational deformity of the femur ranging between 26 and 63 degrees , one had an additional leg-shortening of about 4 cm. Two patients had internal rotational deformities. In two patients with delayed fracture healing union was achieved within one year without secondary surgery. Post-operative clinical assessment and CT-scans revealed good derotation results with deformities of less than 4 degrees in all cases. No device-related complications were observed. Therefore, we conclude that "closed" osteotomy with an intramedullary saw is a minimal-invasive, safe and reliable option for derotation procedures in the femur.

Combination treatment with donor-specific transfusions and cyclosporine a induces long-term survival of cardiac allografts in miniature Swine.

BACKGROUND: To evaluate whether pretransplant donor-specific transfusions (DST) can induce tolerance to cardiac allografts in large animals, heterotopic cardiac transplants were performed across a class I MHC barrier in inbred miniature swine. METHODS: Experimental animals received two DSTs, each containing 1.4x10 viable peripheral blood mononuclear cells, 14 and 7 days prior to transplantation together with a 12-day course of cyclosporine (CyA) (13 mg/kg IV) starting on postoperative day (POD) 0. RESULTS: Untreated (n=2) and DST-only (n=2) treated control animals rejected between POD 6 and 8. Animals treated with CyA alone (n=3) exhibited graft survival to 53, 52 and 59 days. In contrast, the combination of DST and CyA (n=3) led to stable graft function for >200 days. Long-term survivors maintained peripheral CML response against donor antigen. Following DSTs, the donor-specific proliferative response of CD8+ recipient T cells was significantly increased (P=0.011), and a significant number of CD8+ T cells underwent apoptosis (10.1% on POD 0; 5.2% on POD -14; P=0.04). None of the DST-treated animals developed donor-specific antibodies. CONCLUSIONS: These results are the first to demonstrate the ability of DST to induce operational tolerance to cardiac allografts in large animals, and they suggest that peripheral mechanisms of tolerance mediate this effect.

Heart and en-bloc thymus transplantation in miniature swine.

BACKGROUND: Donor-specific tolerance to organ allografts might be induced by cotransplantation of a sufficient amount of vascularized donor thymus. To facilitate donor thymus-induced cardiac allograft tolerance, we have developed a novel technique for heart and en-bloc thymus transplantation in swine. METHODS: Donor heart and en-bloc thymus grafts were prepared by a technique that preserves the entire arterial supply and venous drainage of the right thymic lobe. En-bloc grafts (n = 4) were transplanted heterotopically into the abdomens of major histocompatibility complex-matched miniature swine. Recipients received 12 days of cyclosporine intravenously. Grafts were monitored by palpation, electrocardiographic monitoring, and periodic open biopsy. Engraftment of the donor thymus was demonstrated by measuring the proportion of recipient-type thymocytes in the donor thymus with flow cytometry. RESULTS: All of the heart and en-bloc thymus grafts had normal cardiac contractility and immediate perfusion of the thymus. All en-bloc grafts were accepted for more than 200 days without significant acute cellular rejection or cardiac allograft vasculopathy. Thymic tissue of en-bloc grafts displayed normal architecture and supported thymopoiesis of recipient-type cells. CONCLUSION: We have validated a new technique of donor thymus transplantation that could have utility in human heart transplantation.

Indirect recognition of MHC class I allopeptides accelerates lung allograft rejection in miniature swine.

The role of indirect allorecognition in graft rejection is examined in two experiments using a swine lung transplantation model. First, two swine received class I mismatched grafts without immunosuppression; another two recipients were treated postoperatively with cyclosporine (CsA). These swine exhibited acute and chronic rejection, respectively. All four recipients developed T-cell reactivity to donor-derived class I major histocompatibility complex (MHC) peptides. Second, six swine were immunized with synthetic donor-derived class I allopeptides prior to transplantation. Control groups consisted of nonimmunized recipients (n = 6) and recipients immunized with an irrelevant peptide (n = 3). These recipients all received a 12-day course of post-operative CsA. Swine immunized with allopeptides exhibited accelerated graft rejection, as compared to both control groups (p < 0.01 and p = 0.03, respectively). Within the experimental group, the dominant histologic finding was acute rejection (AR). Obliterative bronchiolitis (OB) was seen in the graft with the longest survival. Both control groups showed a lesser degree of AR, with four out of six nonimmunized swine ultimately developing OB. These studies suggest that indirect allorecognition is operative during lung allograft rejection, and that pre-transplant sensitization to donor-derived MHC allopeptides can accelerate graft rejection.

New strategies for the treatment of chronic rejection.

Chronic allograft rejection is a slow, progressive process characterized by interstitial fibrosis, luminal obliteration and declining organ function, eventually resulting in graft loss. While optimizing the immunosuppressive regimen has improved short-term allograft survival, chronic rejection remains a major cause of late graft loss. Although non-immunological mechanisms can contribute to chronic rejection, there is compelling evidence that major histocompatibility complex-driven processes play a dominant role in the development of the disease. While some immunosuppressive drugs currently in clinical use, such as mycophenolate mofetil and rapamycin, have favorable effects on the incidence of chronic graft failure, the most effective way to overcome chronic rejection may be to induce immunological tolerance.

Feasibility of xeno-transplantation.

Within a relatively short time span, a significant number of barriers to xeno-transplantation have been identified and potential solutions generated; however, the survival rates for pig-to-primate heart transplantation remain modest at best, with the longest functioning heterotopic heart transplant surviving only 99 days and the longest functioning orthotopic heart transplant surviving only 39 days. A great deal of improvement in immunological strategies will be needed to make xeno-transplantation a clinical reality. The most exciting prospect in the near term is the use of organs from homozygous alphaGal knockout pigs. The diversity of the biological pathways involved in the total spectrum of xenograft rejection, however, makes it highly likely that the clinical feasibility of xeno-transplantation will depend on a multipronged approach that incorporates the advantages of genetically eliminating the alphaGal epitope on hyperacute and acute xenograft rejection and the advantages of tolerance induction on cellular and chronic xenograft rejection.

The value of a noninvasive diagnostic approach to mediastinal masses.

BACKGROUND: Mediastinal tumors show a wide variability, and therefore, a standardized diagnostic and therapeutic workup is instrumental. We subdivided mediastinal tumors into nonlymphatic mediastinal tumors (NLMTs), most of which require surgical resection without need of preoperative histology, and mediastinal lymphadenopathy (MLA), requiring surgical biopsy for exact histologic classification. We investigated the accuracy of noninvasive diagnostic studies distinguishing between the two groups of MLA and NLMT. METHODS: A retrospective analysis was performed on patients who had previously undergone surgery on mediastinal tumors. Their data were statistically analyzed (chi2 test, logistic regression analysis), and the values of medical history, physical examination, laboratory tests, and computerized tomography scan discriminating between MLA and NLMT were assessed. RESULTS: Out of 299 patients included in the study, 242 (80.9%) had MLA and 57 (19.1%) had NLMT. Sensitivity and specificity of noninvasive investigations for differentiation of MLA and NLMT were 98.2% and 86.0%, respectively. Whereas the prevalence of thoracic symptoms such as shortness of breath, cough, or chest pain was similar in both groups (MLA, 165 [69.3%]; NLMT, 41 [69.5%]; p = 0.98), systemic symptoms, including fever, night sweats, or weight loss (MLA, 110 [49.8%]; NLMT, 17 [29.3%]; p < 0.01), and signs of inflammation, such as c-reactive protein, erythrocyte sedimentation rate, and leukocytosis (MLA, 202 [85.6%]; NLMT, 34 [57.6%]; p < 0.001), were significantly more common in MLA. CONCLUSIONS: Noninvasive diagnostic procedures, including medical history, physical examination, laboratory tests, and computerized tomographic scan, are highly sensitive in detecting MLAs that should undergo surgical biopsy. Our data suggest confirming all suspected NLMTs by fine needle aspiration (FNA) biopsy before surgery.