The role of cyclosporin in prolonging survival in vascularized bone allografts

It is known that experimental vascularized bone allografts are subject to host rejection. To be useful clinically, this rejection response would need to be controlled. Cyclosporin is a potent immunosuppressant whose precise role in vascularized bone allograft transplantation has not been established. Using a proven reliable vascularized knee allograft model in inbred rats, cyclosporin was used postoperatively both continuously and short term (14 days after transplant) at 10 mg/kg per day as recipient treatment. Across a strong histocompatibility barrier, continuous cyclosporin was required for long-term graft survival. Short-term therapy delayed rejection for 4 to 6 weeks. However, across a weak histocompatibility barrier, short-term therapy was as effective as continuous therapy in achieving long-term graft survival. The implication is that a limited course of cyclosporin may be clinically successful in sustaining vascularized bone allograft survival, provided the genetic disparity between graft and host has been minimized by genetic matching techniques.     

Vascularized bone allograft transplantation in a genetically defined rat model

A heterotopic subcutaneous model for experimental vascularized bone allograft transplantation has been presented. This model uses genetically defined rats and allows serial assessment of graft viability. The reliability of this model has been proven by successful isograft transplantation. This model was used to study the effect of matching at the major histocompatibility complex on vascularized bone allograft survival. Whereas grafts transplanted across a minor histocompatibility barrier survived until sacrifice, grafts transplanted across a major histocompatibility barrier were victims of an acute rejection process. This study, therefore, showed genetic disparity to be a critical determinant of vascularized bone allograft survival. It indicates that primary vascularized bone allografts are as susceptible to rejection as heart and kidney allografts. For these reasons, it can be anticipated that genetic matching will be important in clinical vascularized bone allograft transplantation. The model used in this study should be useful for obtaining further fundamental immunologic information concerning vascularized bone allograft transplantation.     

Vascularized bone allografts: in vitro assessment of cell-mediated and humoral responses

The immunologic consequences of transplantation of vascularized bone allografts have not been previously characterized. In this study, knee allografts, both vascularized and nonvascularized, were transplanted from Lewis rats to Brown Norway rats across a strong histocompatibility barrier. A total of 66 transplants and 8 control animals were evaluated. The vascularized knee grafts consisted of 1 cm of proximal tibia and distal femur with a minimal muscular cuff isolated on the femoral vessels, and these were transplanted to a heterotopic, subcutaneous position on the abdominal wall of the recipient rat. Nonvascularized allografts (identical but without anastomoses) were transplanted for comparison. The cell-mediated response was measured by lymphocytotoxicity assay, and the humoral response was measured by cytotoxic antibody assay, both employing 51Cr-labeled target cells. The timing and intensity of the immune response differed according to the type of graft. The vascularized bone allografts generated significant cell-mediated and humoral responses as early as 5 days posttransplant. A significant humoral response in nonvascularized bone allografts was not apparent until day 14, while cell-mediated response in these grafts was variable. These findings were correlated with the histologic appearance of the grafted tissue. Cyclosporine, which was administered to one group of vascularized bone allografts, resulted in the suppression of both types of immune responses. The histologic appearance of this group resembled that of isografts transplanted as controls. The clinical application of vascularized bone allografts may offer significant advantages over nonvascularized allografts in the reconstruction of massive bone defects. Complications such as nonunion, fracture, and collapse of articular segments seen in nonvascularized allograft transplantation may be avoided by preservation of the blood supply to the graft. Characterization of the immune response to vascularized bone allografts may subsequently allow the manipulation of the host and/or graft tissue and promote graft incorporation.     

Mechanism of thyroid allograft rejection.

Balb/c thyroids, held in organ culture for 26 days, survive and function as well as isografts for greater than 100 days in CBA recipients. Uncultured allografts are totally rejected by 20 days after transplantation. Prolonged allograft survival can also be achieved by the treatment of donor animals with cyclophosphamide prior to harvesting tissues for transplantation. These allografts do not survive as well as 26 day cultured allografts, but cyclophosphamide pretreatment reduces the culture time required to achieve indefinite survival to 7 days. The provision of an allogeneic (LD) stimulus by thyroid tissue that is I-region incompatible with the host does not facilitate the rejection of a tolerated cultured allograft. However, activation of the host immune system by an uncultured graft syngeneic to a tolerated cultured allograft leads to the chronic rejection of the cultured transplant. The transfer of a tolerated cultured allograft back to its strain of origin induces an acute inflammatory reaction that causes tissue damage within the transplant but does not lead to the total destruction of the tissue.     

Virus-induced abrogation of transplantation tolerance induced by donor-specific transfusion and anti-CD154 antibody

Treatment with a 2-week course of anti-CD154 antibody and a single transfusion of donor leukocytes (a donor-specific transfusion or DST) permits skin allografts to survive for >100 days in thymectomized mice. As clinical trials of this methodology in humans are contemplated, concern has been expressed that viral infection of graft recipients may disrupt tolerance to the allograft. We report that acute infection with lymphocytic choriomeningitis virus (LCMV) induced allograft rejection in mice treated with DST and anti-CD154 antibody if inoculated shortly after transplantation. Isografts resisted LCMV-induced rejection, and the interferon-inducing agent polyinosinic:polycytidylic acid did not induce allograft rejection, suggesting that the effect of LCMV is not simply a consequence of nonspecific inflammation. Administration of anti-CD8 antibody to engrafted mice delayed LCMV-induced allograft rejection. Pichinde virus also induced acute allograft rejection, but murine cytomegalovirus and vaccinia virus (VV) did not. Injection of LCMV approximately 50 days after tolerance induction and transplantation had minimal effect on subsequent allograft survival. Treatment with DST and anti-CD154 antibody did not interfere with clearance of LCMV, but a normally nonlethal high dose of VV during tolerance induction and transplantation killed graft recipients. We conclude that DST and anti-CD154 antibody induce a tolerant state that can be broken shortly after transplantation by certain viral infections. Clinical application of transplantation tolerance protocols may require patient isolation to facilitate the procedure and to protect recipients.     

Antigen-induced suppression: The role of Class I major histocompatibility antigens

The role of Class I major histocompatibility (MHC) antigens in the induction of specific suppression of graft rejection has been investigated. Two experimental transplantation models have been used - fully vascularized heterotopic cardiac allografts in the mouse and fully vascularized orthotopic renal allografts in the rat. Preparations of cells expressing Class I MHC antigens, for example highly purified preparations of rat erythrocytes or platelets or mouse L cells (H2k) transfected with the D locus Class I gene of the b haplotype, LDb-1 cells, were used to pretreat recipients prior to transplantation. The function of the allograft was monitored in order to assess any beneficial effects induced by Class I MHC antigens. The results obtained implicate Class I MHC as important in the induction of specific immunosuppression of vascularized allograft rejection.     

Combined CXCR3/CCR5 blockade attenuates acute and chronic rejection

Chemokine-chemokine receptor interactions orchestrate mononuclear cells recruitment to the allograft, leading to acute and chronic rejection. Despite biologic redundancy, several experimental studies have demonstrated the importance of CXCR3 and CCR5 in acute rejection of allografts. In these studies, deficiency or blockade of CXCR3 or CCR5 led to prolongation of allograft survival, yet allografts were ultimately lost to acute rejection. Given the above findings and the specificity of mononuclear cells bearing CXCR3 and CCR5, we hypothesized that combined blockade of CXCR3 and CCR5 will lead to indefinite (>100 days) graft survival in a full MHC-mismatched murine cardiac allograft model. The donor hearts in the control group were rejected in 6 +/- 1 days after transplantation. Combined blockade of CXCR3 and CCR5 prolonged allograft survival >15-fold vs the control group; all allografts survived for >100 days. More importantly, the donor hearts did not display any intimal lesions characteristic of chronic rejection. Further analysis of the donor hearts in the CXCR3/CCR5 blockade group demonstrated graft infiltration with CD4(+)CD25(+) T cells expressing the Foxp3 gene. Depletion of CD25(+) cells in the combined CXCR3 and CCR5 blockade group resulted in acute rejection of the allografts in 22 +/- 2 days. Combined CXCR3 and CCR5 blockade also reduced alloantigen-specific T lymphocyte proliferation. Combined CXCR3 and CCR5 blockade is effective in preventing acute and chronic rejection in a robust murine model. This effect is mediated, in part, by CD25(+) regulatory T cell recruitment and control of T lymphocyte proliferation.     

Prolonged blockade of CD40-CD40 ligand interactions by gene transfer of CD40Ig results in long-term heart allograft survival and donor-specific hyporesponsiveness, but does not prevent chronic rejection

Previous work on blockade of CD40-CD40 ligand interaction in mice and primates with anti-CD40 ligand mAbs has resulted in a moderate prolongation of allograft survival without the development of true allograft tolerance. In this study, we show in rats that adenovirus-mediated gene transfer of CD40Ig sequences into the graft resulted in prolonged (>200 days) expression of CD40Ig and in long-term (>300 days) survival. Recipients expressing CD40Ig displayed strongly (>90%) inhibited mixed leukocyte reactions and alloantibody production at early (days 5 and 17) and late time points (>100 day) after transplantation, but showed limited inhibition of leukocyte infiltration and cytokine production as evaluated by immunohistology at early time points (day 5). Recipients of long-surviving hearts showed donor-specific hyporesponsiveness since acceptance of second cardiac allografts was donor specific. Nevertheless, long-term allografts (>100 days) displayed signs of chronic rejection vasculopathy. Occluded vessels showed leukocyte infiltration, mainly composed of CD4(+) and CD8(+) cells, macrophages, and mast cells. These recipients also showed antidonor CTL activity. Recipients expressing CD40Ig did not show nonspecific immunosuppression, as they were able to mount anticognate immune responses that were partially inhibited at early time points and were normal thereafter. We conclude that gene transfer-mediated expression of CD40Ig resulted in a highly efficient inhibition of acute heart allograft rejection in rats. This treatment induced donor-specific inhibition of certain alloreactive mechanisms in the short-, but not the long-term, which resulted in long-term survival of allografts concomitant with the development of chronic rejection.     

Prolonged local expression of anti-CD4 antibody by adenovirally transduced allografts can promote long-term graft survival

BACKGROUND: Currently, successful transplantation of allografts requires the systemic use of immunosuppressive drugs. These can cause serious morbidity due to toxicity and increased susceptibility to cancer and infections. Local production of immunosuppressive molecules limited to the graft site would reduce the need for conventional, generalized immunosuppressive therapies and thus educe fewer side effects. This is particularly salient in a disease like type 1 diabetes, which is not immediately life-threatening yet islet allografts can effect a cure. METHODS: We studied the efficacy of locally produced anti-CD4 antibody, mediated by adenovirus (Adv-anti-CD4) transduction of islets, to enhance allograft survival. Adenovirus-transduced islets were transplanted under the kidney capsule of diabetic recipients and graft rejection determined by monitoring blood glucose levels. RESULTS: Adv-anti-CD4 transduction of mouse islets afforded protection against allogeneic rejection after transplantation into fully mismatched recipients. In some recipients, the islet allograft survival was prolonged (persisting for at least 15 weeks), corresponding to the prolonged expression of the anti-CD4 antibody. The effect was local, as absence of CD4+ T lymphocytes was observed primarily at the graft site. CONCLUSIONS: Immunosuppressive effects can be restricted locally by our strategy. Local production of a single antibody against one subset of T lymphocytes can protect mouse islets from allograft rejection during transplantation to treat diabetes. Our findings foreshadow that this strategy may be even more effective when a combination of antibodies are used and that similar strategies may prevent xenograft rejection.     

Immunologic and ultrastructural changes during early rejection of vascularized bone allografts

This investigation evaluated ultrastructural changes during the earliest phase of immunologic rejection of vascularized bone allografts in a genetically defined rat model. These results were correlated with the cell-mediated and humoral immunologic responses during this time period. Employing a model for heterotopic allograft transplantation, 33 rats divided into four categories were evaluated. Group I consisted of ungrafted (naive) Lewis and Brown Norway rats; group II consisted of Lewis-to-Lewis vascularized bone isografts; group III consisted of Lewis-to-Brown Norway vascularized bone allografts; and group IV consisted of Lewis-to-Brown Norway vascularized bone allografts in rats receiving cyclosporine (10 mg/kg/day). Experimental animals were sacrificed at 3, 5, and 7 days. Immunologic analysis was performed using a cell-mediated lymphocytotoxicity assay and a complement-dependent cytotoxic antibody assay. The results of this study show that rejection of vascularized bone allografts appears as early as 3 days postoperatively, with osteocytes and vascular endothelium being the first elements affected. This early rejection is probably a manifestation of the humoral response. All changes secondary to rejection were arrested by cyclosporine.     

Vascularized muscle allografts and the role of cyclosporine

This study examined the fate of vascularized muscle allografts using a genetically defined rat model. Its purposes were (1) to analyze the histologic/immunologic responses, (2) to study the effect of cyclosporine on graft survival, and (3) to examine the possibility of inducing tolerance. In rats differing at a major histocompatibility locus, vascularized gastrocnemius muscle transplants were performed based on the sural branches of the femoral artery and vein. Forty-two animals studied were divided into three groups: Group 1, allografts, was treated without cyclosporine; Group 2, allografts, was administered continuous cyclosporine; and Group 3, allografts, was administered cyclosporine for 6 weeks only. Evaluation consisted of gross examination, H&E histology, and immunologic studies (MLC, CML, and complement-dependent 51Cr lysis assay). Lytic units (LU) were derived from the assays and served as the indicator of immune response. Group 1 animals had uniform rejection with intense cell-mediated response (LU 23 to 47) and low humoral response. Group 2 animals had viable allografts throughout with suppressed lytic unit values of 0 to 9 initially, which rose to 14 to 29 at 6 weeks despite continuous cyclosporine treatment. Group 3 animals showed rejection similar to the untreated animals. Autografts were performed as controls and survived indefinitely. Analysis of variance was significant at p less than 0.05. Using a reliable rat model for vascularized muscle allografts, we found that in transplantation across a major histocompatibility barrier, the initial immune response was primarily cell-mediated. Cyclosporine suppressed rejection only when given continuously, and short-term cyclosporine treatment did not induce a tolerant state. These data should be useful for future studies of vascularized muscle allografts.     

Immunological disruption of antiangiogenic signals by recruited allospecific T cells leads to corneal allograft rejection

Corneal transplantation is the most common solid organ transplantation. The immunologically privileged nature of the cornea results in high success rates. However, T cell-mediated rejection is the most common cause of corneal graft failure. Using antiangiogenesis treatment to prevent corneal neovascularization, which revokes immune privilege, prevents corneal allograft rejection. Endostatin is an antiangiogenic factor that maintains corneal avascularity. In this study, we directly test the role of antiangiogenic and immunological signals in corneal allograft survival, specifically the potential correlation of endostatin production and T cell recruitment. We report that 75% of the corneal allografts of BALB/c mice rejected after postoperative day (POD) 20, whereas all syngeneic grafts survived through POD60. This correlates with endogenous endostatin, which increased and remained high in syngeneic grafts but decreased after POD10 in allografts. Immunostaining demonstrated that early recruitment of allospecific T cells into allografts around POD10 correlated with decreased endostatin production. In Rag(-/-) mice, both allogeneic and syngeneic corneal grafts survived; endostatin remained high throughout. However, after T cell transfer, the allografts eventually rejected, and endostatin decreased. Furthermore, exogenous endostatin treatment delayed allograft rejection and promoted survival secondary to angiogenesis inhibition. Our results suggest that endostatin plays an important role in corneal allograft survival by inhibiting neovascularization and that early recruitment of allospecific T cells into the grafts promotes destruction of endostatin-producing cells, resulting in corneal neovascularization, massive infiltration of effector T cells, and ultimately graft rejection. Therefore, combined antiangiogenesis and immune suppression will be more effective in maintaining corneal allograft survival.     

Early chemokine cascades in murine cardiac grafts regulate T cell recruitment and progression of acute allograft rejection

The identification of early inflammatory events after transplant in solid tissue organ grafts that may direct T cell recruitment and promote acute allograft rejection remain largely unknown. To better understand temporal aspects of early inflammatory events in vascularized organ grafts, we tested the intragraft expression of four different chemokines in heterotopically transplanted A/J (H-2(a)) and syngeneic heart grafts in C57BL/6 (H-2(b)) recipient mice from 1.5 to 48 h after transplant. Similar temporal expression patterns and equivalent levels of chemokine expression were observed in both syngeneic and allogeneic cardiac allografts during this time period. Expression of the neutrophil chemoattractant growth-related oncogene alpha (KC) was observed first and reached peak levels by 6 h after transplant and was followed by the monocyte/macrophage chemoattractant protein-1 (JE) and then macrophage inflammatory proteins 1beta and 1alpha. Administration of rabbit KC antiserum to allograft recipients within 30 min of cardiac transplantation attenuated downstream events including intra-allograft expression of the T cell chemoattractants IFN-gamma-inducible protein-10 and monokine induced by IFN-gamma, cellular infiltration into the allograft, and graft rejection. Similarly, depletion of recipient neutrophils at the time of transplantation significantly extended allograft survival from day 8 to 10 in control-treated recipients up to day 21 after transplant. These results indicate the induction of highly organized cascades of neutrophil and macrophage chemoattractants in cardiac grafts and support the proposal that early inflammatory events are required for optimal recruitment of T cells into allografts during the progression of acute rejection of cardiac allografts.     

Evidence for immune responses to a self-antigen in lung transplantation: role of type V collagen-specific T cells in the pathogenesis of lung allograft rejection

We have reported that lung allograft rejection involves an immune response to a native protein in the lung, type V collagen (col(V)), and that col(V)-induced oral tolerance prevented acute and chronic rejection. In support of these findings col(V) fragments were detected in allografts during rejection, but not in normal lungs. The purpose of the current study was to isolate and characterize col(V)-specific allograft-infiltrating T cells and to determine their contribution to the rejection response in vivo. Two col(V)-specific T cell lines, LT1 and LT3, were isolated from F344 (RT1(lv1)) rat lung allografts during rejection that occurred after transplantation into WKY (RT1(l)) recipients. Both cell lines, but not normal lung lymphocytes, proliferated in response to col(V). Neither LT1 nor LT3 proliferated in response to alloantigens. LT1 and LT3 were CD4(+)CD25(-) and produced IFN-gamma in response to col(V). Compared with normal CD4(+) T cells, both cell lines expressed a limited V-beta TCR repertoire. Each cell strongly expressed V-beta 9 and 16, but differed in expression of other V-betas. Adoptive transfer of each cell line did not induce pathology in lungs of normal WKY rats. In contrast, adoptive transfer of LT1, but not LT3, caused marked peribronchiolar and perivascular inflammation in isograft (WKY) lungs and abrogated col(V)-induced oral tolerance to allograft (F344) lungs. Collectively, these data show that lung allograft rejection involves both allo- and autoimmune responses, and graft destruction that occurs during the rejection response may expose allograft-infiltrating T cells to potentially antigenic epitopes in col(V).     

Requirement for donor and recipient CD40 expression in cardiac allograft rejection: induction of Th1 responses and influence of donor-derived dendritic cells

Costimulation through the CD40-CD40 ligand (CD40L) pathway is critical to allograft rejection, in that anti-CD40L mAb therapy prolongs allograft survival. However, the majority of studies exploring CD40-CD40L interactions have targeted CD40L. Less is known about the requirement for donor- and/or host-derived CD40 during rejection. This study assessed the relative contributions of donor and recipient CD40 expression to the rejection process. As the effectiveness of costimulatory blockade may be mouse strain dependent, this study explored the requirement for donor and recipient CD40 expression in BALB/c and C57BL/6 mice. Wild-type (WT) and CD40(-/-) BALB/c recipients readily rejected WT and CD40(-/-) C57BL/6 allografts, and rejection was associated with a prominent Th1 response. In contrast, CD40(-/-) C57BL/6 recipients failed to reject WT or CD40(-/-) BALB/c allografts and did not mount Th1 or Th2 responses. However, injection of donor CD40(-/-) dendritic cells induced both Th1 and Th2 responses and allograft rejection in CD40(-/-) C57BL/6 recipients. Finally, WT C57BL/6 mice rejected CD40(-/-) allografts, but this rejection response was associated with muted Th1 responses. These findings demonstrate that 1) CD40 expression by the recipient or the graft may impact on the immune response following transplantation; 2) the requirement for CD40 is influenced by the mouse strain; and 3) the requirement for CD40 in rejection may be bypassed by donor DC. Further, as CD40 is not required for rejection in BALB/c recipients, but anti-CD40L mAb prolongs graft survival in these mice, these results suggest that anti-CD40L therapy functions at a level beyond disruption of CD40-CD40L interactions.     

Blocking lymphotoxin signaling abrogates the development of ectopic lymphoid tissue within cardiac allografts and inhibits effector antibody responses

Tertiary lymphoid organs (TLOs) may develop within allografts, but their contribution to graft rejection remains unclear. Here, we study a mouse model of autoantibody-mediated cardiac allograft vasculopathy to clarify the alloimmune responses mediated by intragraft TLOs and whether blocking lymphotoxin-β-receptor (LTβR) signaling, a pathway essential for lymphoid organogenesis, abrogates TLO development. TLOs (defined as discrete lymphoid aggregates associated with high endothelial venules) were detectable in 9 of 13 heart allografts studied and were predominantly B cell in composition, harboring germinal-center activity. These are most likely manifestations of the humoral autoimmunity triggered in this model after transplantation; TLOs did not develop if autoantibody production was prevented. Treatment with inhibitory LTβR-Ig fusion protein virtually abolished allograft TLO formation (mean TLOs/heart: 0.2 vs. 2.2 in control recipients; P=0.02), with marked attenuation of the autoantibody response. Recipients primed for autoantibody before transplantation rejected grafts rapidly, but this accelerated rejection was prevented by postoperative administration of LTβR-Ig (median survival time: 18 vs. >50 d, respectively, P=0.003). Our results provide the first demonstration that TLOs develop within chronically rejecting heart allografts, are predominantly B cell in origin, and can be targeted pharmacologically to inhibit effector humoral responses.     

Immunobiology of allograft rejection in the absence of IFN-gamma: CD8+ effector cells develop independently of CD4+ cells and CD40-CD40 ligand interactions

Both wild-type (WT) and IFN-gamma-deficient (IFN-gamma(-/-)) C57BL/6 mice can rapidly reject BALB/c cardiac allografts. When depleted of CD8(+) cells, both WT and IFN-gamma(-/-) mice rejected their allografts, indicating that these mice share a common CD4-mediated, CD8-independent mechanism of rejection. However, when depleted of CD4(+) cells, WT mice accepted their allografts, while IFN-gamma(-/-) recipients rapidly rejected them. Hence, IFN-gamma(-/-), but not WT mice developed an unusual CD8-mediated, CD4-independent, mechanism of allograft rejection. Allograft rejection in IFN-gamma(-/-) mice was associated with intragraft accumulation of IL-4-producing cells, polymorphonuclear leukocytes, and eosinophils. Furthermore, this form of rejection was resistant to treatment with anti-CD40 ligand (CD40L) mAb, which markedly prolonged graft survival in WT mice. T cell depletion studies verified that anti-CD40L treatment failed to prevent CD8-mediated allograft rejection in IFN-gamma(-/-) mice. However, anti-CD40L treatment did prevent CD4-mediated rejection in IFN-gamma(-/-) mice, although grafts were eventually rejected when CD8(+) T cells repopulated the periphery. The IL-4 production and eosinophil influx into the graft that occurred during CD8-mediated rejection were apparently epiphenomenal, since treatment with anti-IL-4 mAb blocked intragraft accumulation of eosinophils, but did not interfere with allograft rejection. These studies demonstrate that a novel, CD8-mediated mechanism of allograft rejection, which is resistant to experimental immunosuppression, can develop when IFN-gamma is limiting. An understanding of this mechanism is confounded by its association with Th2-like immune events, which contribute unique histopathologic features to the graft but are apparently unnecessary for the process of allograft rejection.     

Long-term clinical experience with fresh osteochondral allografts for articular knee defects in high demand patients

Fresh osteochondral allografts are used to repair osteoarticular defects of the knee. For post-traumatic defects recent advances in other techniques for cartilage repair and resurfacing have reduced the role of allograft tissue transplantation to defects larger than 3 cm in diameter and 1 cm in depth. A fresh osteochondral allograft that has been harvested from a donor within 24 h from death and preserved in 4°C for up to 4 days shows 100% viability of the cartilage. The avascular bone remains structurally intact and mechanically strong until it is replaced by host bone or until it is weakened or absorbed. The indications for fresh osteochondral allografts for reconstructive surgery of the articular surface of the knee do not justify the use of immunosuppressive drugs and we therefore believe that surgical vascularization of the grafts should not be carried out. This clinical approach can provide a reconstructive solution for younger higher demand patients where implants are not desirable and arthrodesis is not acceptable. A clinical follow-up study as early as 1975 showed successful early outcomes. More recently, survival analysis found 95% survival at 5 years, 71% at 10 years, and 66% at 20 years. It was learned that older patients, bipolar transplants, improper loading of the graft, and grafts for osteoarthritis and steroid-induced avascular necrosis do not lead to good long-term outcomes. We would like to describe here some of our long-term clinical experience concerning this surgery. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selective blockade of IL-15 by soluble IL-15 receptor alpha-chain enhances cardiac allograft survival

IL-15 is a T cell growth factor that shares many functional similarities with IL-2 and has recently been shown to be present in tissue and organ allografts, leading to speculation that IL-15 may contribute to graft rejection. Here, we report on the in vivo use of an IL-15 antagonist, a soluble fragment of the murine IL-15R alpha-chain, to investigate the contribution of IL-15 to the rejection of fully vascularized cardiac allografts in a mouse experimental model. Administration of soluble fragment of the murine IL-15R alpha-chain (sIL-15Ralpha) to CBA/Ca (H-2k) recipients for 10 days completely prevented rejection of minor histocompatibility complex-mismatched B10.BR (H-2k) heart grafts (median survival time (MST) of >100 days vs MST of 10 days for control recipients) and led to a state of donor-specific immunologic tolerance. Treatment of CBA/Ca recipients with sIL-15Ralpha alone had only a modest effect on the survival of fully MHC-mismatched BALB/c (H-2d) heart grafts. However, administration of sIL-15Ralpha together with a single dose of a nondepleting anti-CD4 mAb (YTS 177.9) delayed mononuclear cell infiltration of the grafts and markedly prolonged graft survival (MST of 60 days vs MST of 20 days for treatment with anti-CD4 alone). Prolonged graft survival was accompanied in vitro by reduced proliferation and IFN-gamma production by spleen cells, whereas CTL and alloantibody levels were similar to those in animals given anti-CD4 mAb alone. These findings demonstrate that IL-15 plays an important role in the rejection of a vascularized organ allograft and that antagonists to IL-15 may be of therapeutic value in preventing allograft rejection.     

Donor modification leads to prolonged survival of limb allografts

Chronic immunosuppression is essential for maintaining human hand transplant survival because composite tissue allografts are as susceptible to rejection as visceral organ allografts. Limb allografts comprise different types of tissues with varying antigenicities, and the immunosuppressive doses required for these allografts are as high or higher than those required for solid organ allotransplantation. In particular, bone marrow is an early target of the host immune response. This study reports on donor limb modification of the marrow compartment leading to prolonged survival of limb allografts.Chimeric limb allografts comprising a Lewis rat vascularized allograft and Brown Norway rat bone marrow were created. These chimeric limbs were transplanted into three recipients: (1) Buffalo rats (n = 12), where the chimeric limb was allogeneic for both vascular graft and bone marrow; (2) Lewis rats (n = 12), where the limb was allogeneic for marrow alone; and (3) Brown Norway rats (n = 12), where the limb was allogeneic for graft alone.This study found that Brown Norway recipients elicited significantly reduced cell-mediated and humoral immune responses in comparison with the Buffalo and Lewis recipients (p < 0.001 and p < 0.01, respectively). The Buffalo and Lewis recipients both elicited high cell-mediated and humoral responses. The Brown Norway recipients also had prolonged survival of limb tissue allograft in comparison with the other experimental groups.