Extension of survival of rat parathyroid allografts by depletion of Ia donor cells plus preoperative cyclosporine

Methods that avoid chronic immunosuppression of transplant recipients must be developed to eliminate the various risk factors associated with such treatment (e.g., increased infections and malignancies). Pretransplant treatment of the graft with anti-Ia serum plus complement to eliminate "passenger cells" is one such method. An alternative approach is short-term treatment of the recipients with cyclosporine (CsA). In this study, parathyroid glands from Lewis X Brown Norway rats were cultured for one week at 37 degrees C and treated with anti-Ia and complement. Treated glands were transplanted into parathyroidectomized, hypocalcemic Wistar-Furth recipients that had received 30 mg/kg of CsA once a day for the three days prior to transplant. At 1 year posttransplant, 67% of the recipients had functional parathyroid allografts. Control rats (no CsA; fresh, untreated glands) rejected their grafts within 28 days. Controls given three days of CsA and transplanted with fresh, untreated glands all had functional grafts for greater than 56 days (median survival: 80.5 days). Prolongation of allograft survival with short-term, preoperative CsA demonstrates the efficacy of immunosuppression given only at the time of antigen presentation. This course of CsA allowed for indefinite graft survival when the recipient received a graft previously cultured and treated with Ia antiserum. These results are encouraging and should be evaluated further to determine whether similar approaches will be useful in human transplants.     

Immunogenicity of parathyroid allografts in the rat: immunosuppressive dosages effective in passenger leukocyte-rich small bowel transplants are not effective in parathyroid gland transplants with few passenger leukocytes

Background and aims The passenger leukocytes harboured within an allograft induce a massive allo-immune response that leads to allograft rejection if not countered by immunosuppression. We compared the response to short-term immunosuppression of parathyroid gland transplants possessing few passenger leukocytes with that of passenger leukocyte-rich small bowel transplants.Methods Heterotopic parathyroid and orthotopic small bowel transplantation was performed in a Wistar Furth-to-Lewis rat strain combination. Immunosuppression with cyclosporine A (CsA) was administered in different dosages for 14 days. Dysfunctional allografts were examined immunohistologically.Results CsA more effectively suppressed the immune response provoked by immunogenic small bowel grafts than that induced by less-immunogenic parathyroid grafts. Immunosuppression with 20 mg/kg per day induced long-term survival in the small bowel (165±21 days) but not in the parathyroid (28±3 days). All rejected grafts featured massive cellular infiltration by activated T cells as a sign of immune rejection.Conclusion Immunosuppressive dosages effective in passenger leukocyte-rich small bowel transplants were not as effective in parathyroid gland transplants harbouring few passenger leukocytes. In spite of the paucity of passenger leukocytes in parathyroid grafts it is more difficult to control by immunosuppression the immune response to them than that to the passenger leukocyte-rich small bowel.S. Timm and C. Otto contributed equally to this study     

Short-term immunosuppression after rat parathyroid allotransplantation

The aim of this study was to evaluate whether short-term postoperative immunosuppression is able to sufficiently prolong graft survival after experimental allogeneic parathyroid transplantation. Heterotopic parathyroid transplantation was performed in 6 groups: 1) syngeneic control Lewis (LEW) to LEW; 2) allogeneic control Wistar-Furth (WF) to LEW; 3-5) WF to LEW plus short-term immunosuppression, postoperative days 1-13 (cyclosporine 5/10/20 mg/kg); and 6) WF to LEW plus 10 mg/kg CyA from preoperative day 7 to postoperative day 7. Graft function was examined up to 60 days; histological and immunohistological examination was performed on all grafts with impaired function. Graft function after syngeneic transplantation was indefinite, while recipients of allogeneic grafts turned hypocalcemic after 13 +/- 2 days. With immunosuppression, graft function was 21 +/- 2 days (groups 5 and 6) and 28 +/- 3 days (groups 3 and 4). Histologically, a cellular infiltrate responsible for graft destruction was found. The results show that indefinite parathyroid allograft survival cannot be achieved by short-term immunosuppression alone. Whether the combination of an additional graft pretreatment and immunosuppression has an impact on graft function will be further examined.     

A short-term combination therapy with cyclosporine and rapamycin or leflunomide induces long-term heart allograft survival in a strongly immunogenic strain combination in rats

Abstract  Synergism between cyclosporine (CsA) and rapamycin (RAPA) or leflunomide (LF) was studied in a strongly immunogenic cardiac allograft model in rats. In the absence of immunosuppression, PVG recipients rejected WKAH heart grafts after a mean survival time (MST) of 5.2 ± 1.1 days. A dose of 7.5 mg/kg per day CsA did not prolong graft survival (MST 5.6 ± 1.2 days). CsA given at 10 mg/ kg per day for 30 days extended MST of the grafts to 48 ± 7 days. A short course of combination therapy consisting of adding a non-therapeutic dose of RAPA or a subthera-peutic dose of LF to a 1-month course of CsA resulted in permanent graft survival. These data suggest that RAPA and LF synergize with CsA enabling not only the lowering of the dose of CsA, but also inducing transplantation tolerance.     

Reversal of diabetes in outbred mice by islet allotransplantation

The combination of donor pretreatment with cyclophosphamide, organ culture in 95% O2:5% CO2 for 7-10 days, and short-term immunosuppression of recipients with cyclosporin A (CsA) were necessary to obtain 100% survival of single-cluster BALB/c islet allografts in outbred mice. In vivo and in vitro pretreatment of the donor tissue alone resulted in the acceptance of 45% of the islet allografts in nonimmunosuppressed outbred mice. CsA treatment of recipients alone yielded 40% survival of the untreated allografts. CsA treatment played an important role in maintaining the capacity of islet allografts to function in outbred mice. During CsA treatment, 88% of streptozocin-treated mice showed graft-dependent reversal of diabetes; the remainder showed no evidence of graft function, and CsA treatment failed to prevent acute graft rejection. After withdrawal of CsA immunosuppression, 38% of this total group remained normoglycemic. These findings suggest that modulation of both donor-tissue immunogenicity and recipient responsiveness will be required for successful pancreatic islet transplantation in diabetic humans.     

Prolongation of allograft survival in diabetic rats treated with cyclosporine by deoxyguanosine pretreatment of pancreatic islets of Langerhans

In vitro pretreatment of islets of Langerhans with deoxyguanosine (dGuo) has been shown to be effective for the prolongation of islet allograft survival in rats. [This study evaluates the effect of pretreatment of islets with dGuo transplanted into CsA-treated recipients.] Transplantation of dGuo-treated islets from Wistar rats into diabetic hooded (PVG) rats resulted in 36% graft survival without immunosuppression (dGuo-group) and 89% islet survival after a short course of cyclosporine was used in recipients (dGuo + CsA group). In contrast, transplantation of untreated islets into rats without immunosuppression (controls) and with CsA (CsA group) immunosuppression resulted in 0 and 56% survival, respectively. The differences in graft survival between dGuo versus control group (P less than 0.001), (dGuo + CsA) versus control group (P less than 0.0001), and CsA versus control group (P less than 0.002) are statistically significant. Donor-strain skin-graft challenge failed to induce rejection of transplanted normoglycemic rats in (dGuo) and (dGuo + CsA) groups. The results indicate that a state of immunologic unresponsiveness may have been induced in the recipients of dGuo-treated islets, and further treatment with CsA synergistically prolongs islet survival in fully mismatched rats.     

Differential response of kidney and pancreas rejection to cyclosporine immunosuppression.

Immunological interferences between kidney and pancreas transplants were investigated in a genetically defined rat model of combined kidney and pancreas transplantation. Kidney and whole-pancreas grafts were transplanted microsurgically either as individual grafts or in a combined technique. Whole pancreas grafts were grafted into streptozotocin diabetic recipients (55 mg/kg bodyweight i.v.) three days after induction of diabetes. The exocrine secretion was suppressed by duct ligation. Rejection of the grafts was defined by recurrence of diabetes in pancreas-grafted recipients and renal failure after kidney transplantation. There were marked differences in the efficacy of identical short-term cyclosporine immunosuppression (15 mg/kg intramuscularly for 14 days): DA kidneys survived indefinitely in LEW rats (MST greater than 100 days), while DA pancreas allografts underwent prolonged but not permanent survival (P less than 0.01) either as individual grafts (MST 27.3 +/- 1,9 days) or when transplanted simultaneously together with the kidney (44 +/- 16 days) (P less than 0.01). LEW rats carrying a DA kidney for 100 days also rejected a subsequent donor-specific pancreas transplant within 30 days. The histological alterations in the kidney were more pronounced than after cyclosporine-induced DA kidney long-term survival alone. By contrast to the rejecting subsequently transferred pancreas, a metachronous second DA kidney was permanently accepted (greater than 100 days) without further immunosuppression after removal of the first graft, while unrelated LEW. 1U kidneys were acutely rejected. In summary, the results indicate that there are not only quantitative differences of kidney and pancreas allograft survival but also differences concerning the state of immunological unresponsiveness induced by identical cyclosporine immunosuppression. While CsA induces donor-specific immunological unresponsiveness after kidney transplantation, pancreas transplants are all eventually rejected after some differential prolongation of survival. Further investigations on the effects of different MHC and minor alloantigens may provide more insight into the complex immunological situation of individual and combined kidney and pancreas transplantation.     

Macrophage depletion prevents anti-graft antibody production and results in long-term survival in xenotransplantation

Liposome-encapsulated dichloromethylene diphosphonate (clodronate) is known to deplete macrophages. We examined the effect of clodronate on xenoreactive antibody production and xenograft rejection. Hamster cardiac grafts were transplanted into Lewis rats. Clodronate (4 mL/kg) was injected intravenously on the day before transplantation. In some groups, cyclosporine A (CsA) at a dose of 15 mg/kg was given daily intramuscularly until the end of each experiment. Untreated Lewis rats rejected the grafts at 2 and 3 days after transplantation. Neither CsA treatment alone nor clodronate treatment alone prolonged graft survival. Five of 7 Lewis recipients treated with clodronate and CsA did not reject hamster hearts for 100 days. Antibody production in the CsA plus clodronate-treated group was suppressed compared with control groups.     

The mechanism of synergistic interaction between anti-interleukin 2 receptor monoclonal antibody and cyclosporine therapy in rat recipients of organ allografts

Untreated anephric LEW rats die ca. 9 days following transplantation of LBNF1 kidney allografts. Although treatment with ART-18, a mouse antirat IL-2R mAb (300 micrograms/kg/day x 10 days), prolonged graft survival to ca. 3 weeks, the severely impaired renal function was comparable to untreated controls (creatinine levels 3-5 mg/dl). In contrast, simultaneous infusion of ART-18 and a very low dose of CsA (0.75 mg/kg x 10 days), marginally effective on its own, resulted in survival of greater than 45 days; the grafts exhibited relatively good function comparable to that in rats treated with full-dose (15 mg/kg/day) CsA. This beneficial biological effect did not depend upon elevated CsA trough levels in animals conditioned with both modalities. The CD4:CD8 ratio at the graft site was lowest (0.3-0.4) in recipients treated with ART-18 + CsA. Synergy between the two agents has been demonstrated by adoptive transfer studies in which nonspecific suppression has been conferred selectively by cells infiltrating kidney grafts in rats given ART-18 and CsA in concert but not separately (LBNF1 and WF test cardiac allograft survival ca. 12 days). In contrast, suppression in the recipient spleens was donor-specific; both CD4 and CD8 cells prolonged test graft survival. Immunohistological evaluation of renal allografts revealed that therapy with ART-18 or low-dose CsA alone failed to deplete IL-2R+ cells and prevent production of IL-2, IFN-g, and TNF. In contrast, the frequency of infiltrating IL-2R+ cells and elaboration of endogenous cytokines in non-uremic hosts receiving combination therapy was greatly depressed, stressing again synergistic interaction between ART-18 and CsA. Additionally, markedly reduced class II antigen induction, XL-fibrin deposition, and glomerulitis may also contribute to prolonged survival and satisfactory function of kidney allografts in this animal group.     

Enhancement of allograft survival by donor-specific transfusion one day prior to transplant. Importance of timing and specificity when DST is given with cyclosporine.

Donor-specific transfusion effects were studied in the ACI-to-Lewis rat heterotopic heart allograft model using cyclosporine immunosuppression. Low-dose CsA for 1 week plus a single fresh or stored DST given 1 day before allografting significantly prolonged graft survival over CsA therapy alone (median survival time 23.5 days vs. 10 days, P less than 0.01), but third-party transfusion did not (11.5 vs. 10 days, NS). When CsA was started at the time of DST and continued for 2 weeks, maximal graft enhancement was achieved after just one DST. DST/CsA was equally efficacious if given on any day before transplantation, provided CsA was started on the same day as the transfusion. However, pretransplant DST given without CsA shortened subsequent graft survival of day -1 DST/CsA treatment (14.5 days, n = 6, vs. 60 days for controls, n = 10; P less than 0.01). The addition of methylprednisolone to the DST/CsA protocol had no effect on graft survival (51 vs. 53 days, P = NS), but extending the period of postoperative CsA therapy for 4 weeks at reduced dose (2.5 mg/kg/day) significantly prolonged median survival (111 days, n = 11) and resulted in 45% permanent engraftment (greater than 120 days survival). CsA permits graft enhancement with a single DST as early as 1 day before grafting. This avoids the risk of sensitization from DSTs and can extend DST use to cadaveric graft recipients.     

Effect of in vitro culture and cyclosporine A treatment on adrenal medulla allograft survival

Adrenal medullary tissue from Wistar-Furth rats was transplanted beneath the renal capsule of Lewis rats to determine the effect of in vitro culture of the donor graft and temporary recipient immunosuppression with Cyclosporine A (CsA) on allograft survival. The adrenal medulla was transplanted immediately after dissection or after 1 week of culture, either at 24 degrees C or in the presence of 95% O2 at 37 degrees C. The results showed that neither cultural pretreatments affect the survival of the isografts as indicated by morphologic integrity of the grafts 30 days after transplantation. In the absence of in vitro culture of the donor medulla and short-term CsA recipient treatment, all the allografts were completely rejected at 30 days. Cultural pretreatment of the grafts either at 24 degrees C or in the presence of 95% O2, in conjunction with temporary CsA treatment of the recipient, or CsA treatment alone produced histologic survival of the grafts 30 days after transplantation. Varying degrees of lymphocytic infiltration were present in the grafts. When adrenal cortex was transplanted in conjunction with medullary tissue a bimodal immune reaction was observed; medullary tissue was infiltrated by lymphocytes, while the adrenal cortex remained morphologically intact with no infiltration at all. The experiments performed did not show a benefit in prolonging medulla allograft survival using pretransplant culture of the tissue.     

Detection of chimerism following vascularized bone allotransplantation by polymerase chain reaction using a Y-chromosome specific primer.

Chimerism following allogeneic organ transplantation is a phenomenon known to occur and be associated with development of immunologic tolerance in allotransplantation. However, little is known about graft cell migration following vascularized bone allografting. In this study, chimerism was assessed following vascularized tibia transplantation from male DA or PVG donors to female PVG rat recipients using a semi-quantitative polymerase chain reaction for the Y-chromosome. FK-506 (Tacrolimus) was administered after transplantation for immunosuppression. All immunosuppresssed PVG rat recipients of PVG bone grafts showed a high level of chimerism (1%) in the thymus, spleen, liver and cervical lymph nodes at 18 weeks post-transplant. Donor cells were also detected in the contralateral tibia and humerus. In non-immunosuppressed PVG rat recipients of DA bone grafts, donor cells were detected in the spleen in three of five rats within 2 weeks post-transplant. In these animals the bone grafts were severely rejected. In immunosuppressed PVG rat recipients of DA bone grafts, two of five, four of eight and eight of 10 rats showed low level chimerism (0.1%) in peripheral blood at 1, 12, and 18 weeks post-transplant. Six rats showed a high level of chimerism in the spleen and thymus. Histological studies revealed no rejection findings through 18 weeks post-transplant. Our results indicate that chimerism, or the presence of graft cells in host tissue, may occur in the face of acute rejection and be demonstrable following vascularized isograft and allograft living bone transplantation when chronic immunosuppression is maintained. Graft vascular patency during the short-term likely allows cellular migration, even in the face of acute rejection. Long-term survival and proliferation of graft marrow elements in host tissue may be possible with adequate immunosuppression.     

Effect of ultraviolet-B-irradiated donor-specific blood transfusions and peritransplant immunosuppression with cyclosporine on rat cardiac allograft survival

We have previously demonstrated that pretreatment of ACI recipients with ultraviolet-irradiated donor-specific blood transfusion (UV-DST) leads to permanent cardiac allograft survival without further host immunosuppression (ACI rats are weak responders to Lewis lymphocytes in mixed-lymphocyte reaction). This study examines the effect of UV-DST and the timing of transfusions on ACI cardiac allograft survival in Lewis recipients with and without the addition of peritransplant cyclosporine (CsA) (20 mg/kg i.m.) given on days 0, +1, and +2 in relation to the time of transplantation. The mean survival time (MST) of ACI cardiac allografts in Lewis recipients was significantly increased to 33.6 +/- 5.7 days (P less than 0.001) by CsA treatment alone as compared to 6.5 +/- 0.5 days survival in control. When DST was given on day -3 combined with CsA, graft survival was increased to 42.0 +/- 9.3 days (P less than 0.01), as compared to 5.8 +/- 1.3 days when DST alone was used. When DST was irradiated with ultraviolet B (UV-DST) and administered on day -3 combined with peritransplant CsA, the MST was increased to 68.83 +/- 16.1 days as compared to an MST of 10.0 +/- 1.0 days in controls treated with UV-DST alone. When UV-DST was given on day -7 and combined with peritransplant CsA immunosuppression, the results were similar. However, when UV-DST was peritransplant CsA course, 4 of 6 recipients maintained their ACI heart allografts indefinitely (greater than 300 days) in contrast to the effect of UV-DST alone (MST of 13.5 days). Third-party (W/F) UV-irradiated blood transfusions were ineffective in prolonging ACI cardiac allografts in Lewis rats, regardless of whether the transfusions were given alone or in combination with peritransplant immunosuppression with CsA. In conclusion, these results demonstrate that UV-DST combined with a brief peritransplant immunosuppression with CsA induces prolonged heart allograft survival in a histoincompatible, strong responder host, and that such effect is donor specific. The use of UV-DST combined with peritransplant CsA immunosuppression offers a promising approach to achieving organ transplant unresponsiveness, and decreased sensitization to the donor blood elements, which eventually may have important clinical implications.     

Effect of anti-Ia antibodies, culture, and cyclosporin on prolongation of canine islet allograft survival

Evidence in rodents suggests that islet pretreatment to reduce islet immunogenicity will also require some form of immunosuppression of the recipient for islet allograft acceptance in highly reactive donor-recipient pairs. We attempted to ascertain whether outbred dogs would also require treatment of both donor islets and the recipient to prolong islet allograft survival. Untreated canine islets are uniformly rejected in 6-10 days in beagles. Tissue culture alone, at 37 degrees C for 7 days, or treatment of freshly prepared islets with anti-Ia monoclonal antibodies (MoAbs) (B1F6 + 7.2) did not prolong canine islet allograft survival. Treatment of culture-maintained canine islets with anti-Ia MoAbs plus complement resulted in prolongation of islet allograft survival for 188 and 368 days in two of seven pancreatectomized nonimmunosuppressed beagles. The administration of low doses of cyclosporin A (CsA) intramuscularly, to recipients of untreated canine islet allografts had no effect on graft survival. By contrast, six of nine CsA-treated recipients of islets that were also treated with anti-Ia MoAbs (B1F6 + 7.2) plus complement showed prolongation of graft survival. Euglycemia was sustained for 19, 34, 89, and 300 days after the CsA was discontinued (day 30) in four of these animals. Two animals had unstable grafts from the beginning that failed 23 and 29 days after transplantation. Our results indicate that simple maneuvers like short-term tissue culture at 37 degrees C and treatment of freshly isolated islets with anti-Ia MoAbs and complement are inadequate to prevent rejection in outbred pancreatectomized beagles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of donor-specific unresponsiveness to rat cardiac allograft by donor leukocytes and cyclosporine

Many recent reports have emphasized the importance of donor antigens in the induction of allograft tolerance. This study examines the effect of pretransplant infusion of 10(8) donor leukocytes (DL) combined with peritransplant cyclosporine (CsA) on W/F cardiac allograft survival in Lewis rats. Peritransplant recipient treatment consisted of CsA 20 mg/kg given i.m. on days 0, +1, and +2 relative to heart transplantation. Lewis recipients, 5-8 per group, were pretreated with 10(8) DL with or without peritransplant CsA. A single DL transfusion on day -3 or day -7 prior to transplantation significantly prolonged the mean survival time (MST) of W/F hearts from 7.0 +/- 0.9 days in controls to 12.2 +/- 4.5 days and 12.4 +/- 1.0 days (P less than 0.01), respectively. Two DL infusions on days -7 and -3 or on days -14 and -7 prolonged the MST to 10.6 +/- 1.3 days (P less than 0.02) and 16.4 +/- 2.8 days (P less than 0.001), respectively. The administration of peritransplant CsA alone significantly prolonged W/F heart allograft survival to 43.1 +/- 2.7 days. When pretransplant DL transfusion on day -3 was combined with CsA treatment, 4/8 animals maintained their grafts indefinitely (greater than 100 days). Similarly, DL infusion on day -7 with peritransplant CsA led to indefinite graft survival in 3/5 animals. Administration of DL on days -7 and -3 combined with CsA resulted in indefinite graft survival (greater than 100 days) in 4/6 animals. Transfusion of DL on day -3 alone or in combination with peritransplant CsA, had no effect on a third-party (ACI) heart allograft survival prolongation compared with appropriate controls. To define the underlying mechanisms responsible for donor-specific unresponsiveness in this model, pooled sera and unseparated spleen cells were passively transferred from recipients of long-term cardiac allografts to syngeneic rats receiving donor-type (W/F) or third-party (ACI) cardiac allografts. Transfer of serum (1 ml on days 0, and 1, 0.5 ml on days +2, +3, and +4) from ungrafted recipients of DL on days -14 and -7 led to significant donor graft survival of 9.8 +/- 0.4 days (P less than 0.02) in unmodified hosts. Similarly, passive transfer of serum obtained at 20 and 100 days after transplantation significantly prolonged the MST of donor-type hearts in syngeneic untreated hosts to 11.3 +/- 0.8 and 10.0 +/- 1.1 days, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Allotransplantation of dispersed single pancreatic endocrine cells in diabetic rats

Dispersed pancreatic endocrine cells (PECs) were recently shown to survive indefinitely in the brain of allogeneic diabetic rat recipients across the major histocompatibility barrier without immunosuppression. Purified PECs (2-3 X 10(6) cells) prepared from Wistar rat islets were transplanted in 10 different sites in streptozocin-induced diabetic ACI rats. Blood glucose and body weight changes were monitored throughout the study. PEC isografts (n = 5) and allografts (n = 6) were nonfunctional when transplanted in intramuscular, intravenous, and intrahepatic sites. When transplanted intraportally (n = 6) and intraperitoneally (n = 6), similar grafts were functional but had a short survival period (6.6 +/- 1.5 and 15.3 +/- 16.6 days, respectively). Prolonged graft survival in some recipients was observed when kidney capsule [5, 9, 10, 240, 282, and 300 (2 rats) days], omentum pocket (7, 8, 10, 90, 105, 154, 155, and 157 days), and testis (7, 8, 12, 150, 230, and 234 days) were the transplantation sites. Permanent graft survival was achieved in 20 of 20 recipients with intracerebral transplantation and 21 of 22 recipients with intrathecal transplantation. These findings confirm that dispersed single PECs can be transplanted as a permanent functional graft and can normalize the hyperglycemia of the diabetic recipients. The duration of PEC graft survival is variable and depends on the transplantation site. Both the cerebral cortex and subarachnoid space, which are immunologically privileged sites, have provided the best allograft protection.     

Accommodation after lung xenografting from hamster to rat

BACKGROUND: Long-term xenograft survival can be achieved in hamster hearts transplanted into rats treated with cobra venom factor (CVF) and cyclosporine A (CsA). This phenomenon of "accommodation" is associated with expression of protective genes such as bcl-2, bcl-X(L), and heme-oxygenase-1. We examined whether accommodation could be induced in hamster-to-rat lung xenografts and whether the pattern of protective genes is similar to cardiac xenografts. METHODS: We used hamster-to-rat cardiac and lung xenotransplantation models. Cardiac xenotransplants were treated with CVF+CsA and compared with untreated controls. Lung xenotransplants were treated with either CVF+CsA or FK506 and cyclophosphamide (Cp) and compared with untreated controls. All recipients were killed by 21 days after transplantation. We examined graft survival and protein expression of protective genes, and we performed histologic and immunohistologic analyses. RESULTS: Rejection occurred rapidly in untreated rats. CVF+CsA or FK506+Cp treatment significantly influenced graft survival. Eight of 12 CVF+CsA-treated heart transplants survived 21 days. Seven of 16 CVF+CsA-treated lung grafts and five of 12 FK506+Cp-treated lung xenografts survived 21 days. We observed significant protein expression of bcl-2, bcl-X(L), and heme-oxygenase-1 in cardiac xenografts treated with CVF+CsA at 2, 14, and 21 days after transplantation, compared with normal hamster hearts. We also observed significant expression of these proteins in lung xenografts treated with either CVF+CsA or FK506+Cp at 21 days after transplantation, compared with normal lungs. CONCLUSIONS: Accommodation may be a general phenomenon for all organs, mediated through protective genes. Induction of accommodation does not require disruption of the complement system.     

Additive immunosuppressive effect of hydroxycamptothecin and cyclosporine on rejection of heart transplantation in rats

OBJECTIVE: The objective of this study was to study the inhibitory effects of hydroxycamptothecin (HCPT) and cyclosporine (CsA) on heart transplantation rejection in rats. MATERIALS AND METHODS: Inbred SD rats were used as donors and inbred Wistar rats as recipients. Cervical heterotopic heart transplantation was performed in 40 rats: group A received placebo; group B, HCPT; group C, CsA; group D, HCPT+CsA. RESULTS: The mean survival time was prolonged in group D with 5 grafts beating at more than 730 days. CONCLUSION: HCPT combined with CsA prevented acute rejection of allogeneic heart transplantations in rats, significantly prolonging graft mean survival time.     

T suppressor cells induced by transfusions and cyclosporine. Studies in the murine cardiac allograft model

Pregraft transfusion combined with immunosuppression at the time of grafting improves the survival of clinical and experimental allografts. The mechanisms responsible for this effect were investigated in the murine model of cardiac transplantation, combining transfusions 7 to 30 days prior to transplantation with cyclosporine 100 mg/kg, 7 to 20 days pregraft or on days 0, 4, and 6 after grafting. Pregraft DST, third-party blood, and CsA all improved graft survival in the BALB/c-to-CBA donor-recipient combination. In animals treated with DST at 14 days pregrafting, 4/9 grafts survived for greater than 100 days. In those given C57BL/6 blood, or CsA on days 0, 4, 6 postgraft, 1/9 grafts survived for greater than 100 days. When 10(7) spleen cells from DST-treated CBA mice with long-surviving BALB/c heart grafts were transferred to naive CBA mice that then received a BALB/c heart 24 hr later, the transferred cells prolonged graft survival, with all grafts functioning at greater than 40 days, and 4/7 at greater than 100 days. Selective removal of T cells from the spleen cell population prior to transfer showed that L3T4+ T cells, but not Ly-2+ T cells, were required to maintain BALB/c allografts. Combining a short course of CsA with DST was more effective than either treatment alone. The most effective combined treatment was DST at day -14 with 100 mg/kg CsA given on days 0, 4, and 6 postgrafting (8/10 grafts survived greater than 100 days). This treatment also induced splenic suppressor T cells of the L3T4+ Ly-2- phenotype. These results clearly show that L3T4+ splenic T suppressor cells are induced by donor-specific blood transfusion with or without CsA treatment, and that these cells play a role in maintaining long-term tolerance to allografts in the mouse heart transplant model.