Humoral immunity in allograft rejection. The role of cytotoxic alloantibody in hyperacute rejection and enhancement of rat cardiac allografts

The role of humoral immunity in graft rejection in the rat model remains controversial. Passive transfer of cytotoxic alloantibody (CAA) has resulted either in hyperacute rejection or in graft enhancement. This study examines the effect of transfer of CAA on cardiac allograft survival in three rat strain combinations that are fully mismatched at the major histocompatibility (MHC) loci. Strain-specific immune responsiveness in donor-recipient pairs varied from low (Lewis-to-ACI) to high (ACI-to-Lewis) as measured by mixed lymphocyte reactions. CAA was obtained from rats sensitized by three successive skin grafts at weekly intervals. Group 1 (high responder recipients), which consisted of Lewis rats presensitized to ACI and had a lymphocytotoxicity titer of 1:512 to 1:2048, rejected ACI cardiac allografts in 10.8 +/- 7.2 hr compared with 6.5 +/- 0.5 days in naive controls (p less than 0.001). Injection of 1 ml of high-titer CAA into naive Lewis rats immediately after ACI cardiac grafting led to hyperacute rejection of ACI hears in 2.1 +/- 0.8 hr while 1 ml of CAA followed by 2 ml of guinea pig complement (GPC) resulted in even faster rejection (mean survival time (MST) of 23.8 +/- 4.7 min). Injection of 2 ml GPC alone or in combination with 1 ml naive Lewis serum had no effect on graft survival. Multiple pretransplant injections of 1 ml of CAA on days -3, -2,-1, and 0 relative to transplantation resulted in significant prolongation of allograft survival (MST of 10.3 +/- 0.3 days; P less than 0.01). In group 2 (intermediate responder recipients), where Lewis rats were presensitized to WF strain and where cytotoxicity titer was 1:16 to 1:256, the recipients rejected WF hearts in 23.8 +/- 5.8 hr compared with 6.8 +/- 0.8 days in unsensitized control recipients (P less than 0.001). Injection of 1 ml of Lewis anti-WF CAA resulted in prolonged graft survival of 9.7 +/- 3.5 days, while injection of 1 ml of CAA followed by 2 ml of GPC caused hyperacute rejection in 104 +/- 61.7 min. Pretransplant injections of CAA on days -3, -2, -1, and 0 resulted in enhancement, with an MST of 16.3 +/- 1.3 days (P less than 0.001). In group 3 (low responder recipients), ACI presensitized to Lewis developed a cytotoxicity titer of 1:2 to 1:32 and rejected Lewis hearts in 5.3 +/- 0.4 days compared with 10.6 +/- 1.0 days in naive recipients.(ABSTRACT TRUNCATED AT 400 WORDS)     

The effect of soluble complement receptor type 1 on hyperacute xenograft rejection

In the guinea pig-to-rat model of hyperacute xenograft (Xg) rejection, the effect of complement inhibition using systemically administered soluble complement receptor type 1 (sCR1) on discordant cardiac Xg survival was investigated. In PBS-treated control Xg recipients (n = 13), hyperacute rejection was rapid, with a mean Xg survival of 17 +/- 4 min. Therapy with sCR1 prolonged survival of cardiac Xgs in a dose-dependent manner. A 3 mg/kg bolus of sCR1 (n = 4) prolonged Xg survival to 64 +/- 29 min (not significant). Increasing the sCR1 dose to 5.9 mg/kg (n = 4) significantly delayed Xg rejection to 71 +/- 17 min (P-0.026, log-rank test vs. control). In 10 recipients treated with 15 mg/kg sCR1, mean Xg survival was further prolonged to 189 +/- 36 min (P-0.0004) with no adverse effects. While 2 of 8 recipients receiving 60 mg/kg sCR1 died with functioning Xgs at 30 and 300 min due to anastomotic bleeding, Xg survival averaged over 12 hr (747 +/- 100 min, P-0.0004) in the remaining 6 recipients. sCR1 administration significantly inhibited serum complement activity in a parallel dose-dependent fashion, with the 60 mg/kg dose reducing complement activity by 95 +/- 1 and 96 +/- 1% five and 30 min following Xg reperfusion, respectively. Immunofluorescence microscopy revealed rat IgM bound to all cardiac Xgs in control as well as sCR1-treated recipients. In addition, serial histologic examination of cardiac Xgs harvested within 21 min of graft reperfusion revealed occlusive platelet aggregates within the coronary vessels as well as interstitial hemorrhage and myocardial necrosis in Xgs from control recipients, all of which were only minimally present in Xgs from recipients treated with sCR1. These studies show that complement inhibition with sCR1 significantly delays hyperacute cardiac Xg rejection in this discordant model and may be an important component in a therapeutic protocol for xenotransplantation.     

Sensitized B lymphocytes contribute to acute allograft rejection

The contribution of sensitized B lymphocytes to second-set allograft rejection has been relatively ignored despite their regular appearance in rejecting allografts. This study presents evidence that adoptively transferred sensitized B lymphocytes accelerate the rate of acute allograft rejection in a sublethally irradiated rat cardiac allograft model. Donors of reconstituting B lymphocytes were sensitized with three consecutive ACI skin grafts. Transplantation of a heart from an ACI strain donor into a Lewis strain recipient (complete RT1 mismatch) results in rejection in 6.8 +/- 0.3 days. When the allograft donor and recipient are irradiated with 650 cGy prior to transplantation, rejection occurs at 31.5 +/- 3.0 days. Irradiated recipients reconstituted with 10(6) syngeneic sensitized splenic B cells reject their grafts in 20.1 +/- 2.0 days, while reconstitution with 10(6) unsensitized syngeneic B cells has no effect on the rate of rejection (P = 0.0007). These data strongly suggest that sensitized B lymphocytes have a marked accelerating effect on the tempo of allograft rejection.     

Hepatic transplantation into sensitized recipients. Demonstration of hyperacute rejection

Hepatic transplantation into humorally presensitized patients has occasionally been performed without reported accelerated rejection. To study survival of orthotopic hepatic transplants in sensitized recipients a series of studies in rats were performed. Lewis rats sensitized by three successive skin grafts from fully allogeneic ACI strain donors then underwent orthotopic hepatic transplantation from ACI donors. Nine of ten recipients died within 4 hr with bleeding from the liver surface. By comparison, nine unsensitized recipients survived a mean of 10.7 +/- 0.5 days before succumbing with cellular rejection. Death of the sensitized recipients was not due to coagulopathy or technical failure. Histological studies of hyperacutely rejected livers demonstrated marked hemorrhage, edema, congestion, and necrosis within the hepatic parenchyma. There was a relative lack of cellular infiltrate compared with livers rejected by unsensitized recipients. Immunofluorescent staining showed IgG bound to perivascular tissues and sinusoids, and complement bound to perivascular tissue. Serum from presensitized, but not control, recipients showed a high titer of donor-specific, complement-dependent cytotoxic activity. It is concluded that hyperacute rejection of hepatic transplants can occur in sensitized rats and is mediated by a humoral mechanism. The immunohistopathology of this process is described.     

Immunopathogenesis of accelerated allograft rejection in sensitized recipients: humoral and nonhumoral mechanisms

INTRODUCTION: Accelerated rejection (AccR) in sensitized recipients (second-set rejection) is considered a classic humorally mediated form of allograft rejection, although additional effector mechanisms may be involved. METHODS: We developed a model of AccR in which C57BL6 mice are sensitized by BALB/c skin grafts, followed 10 days later by transplantation of BALB/c hearts. We undertook analysis of various humoral and cellular components in this model using knockout or monoclonal antibody-treated allograft recipients. RESULTS: Sensitized mice rejected cardiac allografts in 34+/-7 hr. AccR was accompanied by endothelial deposition of immunoglobulins, complement, and fibrin, but also by dense expression of multiple chemokines and a mixed polymorphonuclear and mononuclear cellular infiltrate. Whereas neutrophil or complement depletion had no significant effect on the tempo of AccR, surprisingly B cell-deficient recipients still underwent AccR (41+/-7 hr) in conjunction with T cell and macrophage recruitment. In contrast, T cell-deficient (nude) mice maintained functioning cardiac allografts for >720 hr despite prior skin engraftment. CONCLUSIONS: AccR in sensitized experimental recipients involves multiple effector pathways. Although most previous studies have emphasized the key role of humoral pathways in mediating AccR, our data indicate that T cell-dependent mechanisms can also promote AccR, alone or in conjunction with humoral responses.     

sCR1sLe(X) reduces lung allograft ischemia-reperfusion injury but does not ameliorate acute rejection.

BACKGROUND: Combined inhibition of complement and leukocyte adhesion by sCR1sLe(X) reduces lung allograft dysfunction up to 24 h. In the present study its effect on graft function and acute rejection was evaluated up to 5 days after experimental transplantation. METHODS: Orthotopic single left lung transplantation was performed in 35 male rats (Brown Norway to Fischer 344) after a total ischemic time of 20 h. Two groups were assessed after 1, 3, and 5 days post-transplant, respectively (n=5 per group and time point): controls vs. recipients which received 10 mg/kg sCR1sLe(X) 15 min prior to reperfusion. In addition, five animals received 10 mg/kg per day sCR1sLe(X) for 5 days. For blood gas analysis of the graft, the contralateral lung was occluded for 5 min to assess graft function. Lung grafts were flushed, and histological grading was performed in blinded fashion according to the International Society for Heart and Lung Transplantation criteria. RESULTS: Graft PaO(2) in recipients treated with sCR1sLe(X) was superior on day 1 (383+/-118 vs. 56+/-15 mmHg; P<0.0001) and day 3 (446+/-48 vs. 231+/-108 mmHg; P<0.0001). Five days after transplantation, no difference in PaO(2) was found (61+/-28 vs. 83+/-31 mmHg; P=0.59). Repeated treatment with sCR1sLe(X) for 5 days did not improve PaO(2) (64+/-5 mmHg; P=0.65 vs. control; P=0.93 vs. sCR1sLe(X)). At any time point, there was no difference in the degree of rejection between groups. CONCLUSIONS: In this model sCR1sLe(X) provided marked improvement of graft function up to 3 days, but inhibition of both complement system and selectin dependent leukocyte adhesion failed to protect against acute rejection.     

Antigenicity of venous allografts.

With isolated exceptions, the clinical use of venous allografts has been disappointing. Considerable evidence indicates that allograft antigenicity plays a major role in the failure of venous allografts when used as arterial replacements. Recent reports suggest that DMSO-cryopreservation of venous allografts may reduce allograft antigenicity while preserving allograft viability. The present study examines the effect of modifications of vein allografts on subsequent allograft antigenicity. Skin grafts were transplanted from ACI to Lewis inbred strains of male rats. Primary skin graft rejection occurred in 9.0 +/- 1.0 days. Subcutaneous implantation of fresh inferior vena cava from ACI rate into Lewis rats resulted in subsequent skin graft rejection in 5.0 +/- 1.0 days, confirming the antigenicity of venous tissue. Cryopreservation of ACI inferior vena cava for seven days prior to implantation, with or without 15% DMSO, resulted in subsequent skin graft rejection in 5.0 +/- 1.0 days. Treatment of ACI inferior vena cava with 0.30% gluteraldehyde for 20 minutes prior to implantation in Lewis rats resulted in skin graft rejection in 9.0 +/- 1.0 days, the same time as a first set rejection. This study indicates that unmodified veins are normally antigenic and that this antigenicity is not eliminated by cryopreservation with or without DMSO. Gluteraldehyde treatment appears to reduce allograft antigenicity, but results in a nonviable graft. At the present time, there is no known way to reduce the antigenicity of viable venous allografts.     

Recirculation of indium-111-labeled lymphocytes in normal and allografted rats

The kinetics of lymphocyte recirculation in normal and allografted rats with acute cardiac rejection was studied with indium-111 (In-111) labeled splenic lymphocytes in two groups of rats. Group 1 consisted of subgroups of normal Lewis rats infused with In-111 labeled unsensitized syngeneic cells (group 1a); ACI-sensitized syngeneic cells (group 1b); and ACI spleen cells (group 1c). Four rats from each subgroup were killed at 3, 6, 18, and 24 hr after cell infusion for blood, spleen, mesenteric lymph node (MLN), thymus, bone marrow (BM), liver, kidney, muscle, and heart scintillation counts. Group 2 consisted of Lewis recipients of ACI cardiac allografts infused with normal or with ACI-sensitized syngeneic splenic cells. Four rats from each subgroup were killed daily until rejection (day 7) for isotope counts of various organs. In ungrafted rats (group I), splenic accumulation of unsensitized syngeneic cells fell from 50% of the total injected dose/g tissue at 3 hr to 28% at 24 hr, whereas it rose from 12% at 3 hr to 39% at 24 hr in MLN. In contrast, the sensitized syngeneic and allogeneic cells homed preferentially to the spleen with insignificant accumulation in the MLN throughout the experiment. The BM and liver showed moderate accumulation while the thymus and nonlymphoid organs had low concentrations of labeled cells at all times. Splenic accumulation of unsensitized syngeneic cells in allografted rats (group II) showed a steep rise from day 1, reaching a peak at day 3, followed by a plateau--but sensitized cells demonstrated a peak on day 4 followed by a sharp decline until rejection. Accumulation of unsensitized cells in the MLN was significantly higher (P less than 0.001) than that of sensitized cells throughout the study. There was a significant fall (P less than 0.001) in radioactivity of BM, thymus, liver, and nonlymphoid organs from days 1-7, and the cardiac allograft demonstrated a reciprocal sharp rise in radioactivity. There was a significant early accumulation (P less than 0.001) of sensitized cells compared with unsensitized cells in the cardiac allograft on day 1. This study shows that In-111 labeled donor cells bearing surface antigen different from that of the recipient were sequestered from the circulating pool and immobilized in the spleen, but labeled donor cells with similar surface antigen to that of the recipient were recruited into the lymph node lymphocyte recirculating pool. It further demonstrates the difference in migration patterns of normal and sensitized syngeneic cells during acute allograft rejection.     

Infectious tolerance mediated by CD8+ T-suppresor cells after UV-B-irradiated donor-specific transfusion and rat heart transplantation

AIMS: CD8+CD28- human T-suppressor cells (Ts), which can be generated in vitro, act directly on APC rendering them tolerogenic to unprimed and primed CD4+ T cells. The aim of this study was to investigate the possibility that CD8+ T cells mediate the induction of tolerance in a heart transplantation model in rodents. MATERIALS AND METHODS: Blood from Lewis rats was UV-B-irradiated and transfused into ACI recipients on days -21, -14, and -7 before heart allograft transplantation on day 0. CD4(+) and CD8(+) T cells were positively selected from ACI rats, which had tolerated Lewis heart allografts for more than 100 days and were adoptively transferred to naive ACI rats pretreated (day -1) with gamma irradiation. These ACI rats underwent transplantation with Lewis hearts 24 hours after adoptive transfer of putative T-suppressor cells. RESULTS: Adoptive transfer of CD8(+) T cells from tolerant ACI to naive ACI rats significantly prolonged Lewis heart mean allograft survival time (MST +/- SD) to 69 +/- 13 days as compared with 15 +/- 1 and 14 +/- 1 days in animals adoptively transferred with CD4+ T cells or untreated controls, respectively (P < .001). Similarly, adoptive transfer of CD8(+) T cells from secondary ACI recipients to naive syngeneic animals also significantly prolonged survival of heart allografts to MST +/- SD of 72 +/- 4 for CD8(+) and 15 +/- 4 days for CD4(+) T cells (P < .001). CONCLUSIONS: These data demonstrate that allogeneic tolerance induced in ACI recipients by treatment with UV-B-irradiated blood from Lewis donors is mediated by CD8+ T-suppressor cells.     

Prolonged cardiac allograft survival in presensitized rats after a high activity Yunnan-cobra venom factor therapy

Complement-dependent antibody-mediated acute humoral rejection is the major obstacle of clinical transplantation across ABO incompatibility and human leukocyte antigen presensitization. We previously demonstrated that Yunnan-cobra venom factor (Y-CVF) could almost completely abrogate complement activity and successfully prevent hyperacute rejection in some xenotransplant models without any obvious toxicity. In this study we investigated whether depletion of complement by Y-CVF prevented acute humoral allograft rejection in presensitized rats thereby prolonging graft survival. METHODS: Presensitization was achieved in Lewis rats by sequential grafting of three full-thickness skin pieces from Brown Norway rats. Serum cytotoxic alloantibody titers were determined by a modified in vitro complement-dependent microcytotoxicity assay. After presensitization, each Lewis rat received a heterotopic Brown Norway cardiac allograft. Fifteen recipients were divided into two groups: (1) no treatment control (n = 7); (2) Y-CVF therapy group (86 u/kg, IV, day -1) (n = 8). After cessation of the heart beat, allograft rejection was confirmed by pathologic as well as IgG and C3 immunohistochemical examinations. RESULTS: The mean graft survival time was significantly prolonged to 99.50 +/- 38.72 hours among rats that received Y-CVF vs 12.71 +/- 13.94 hours in nontreated controls (P < .001). Upon pathological and immunohistochemical examination, acute humoral rejection was mainly exhibited in the control group, whereas acute cellular rejection was mainly displayed in the Y-CVF therapy group. CONCLUSIONS: Our study demonstrated that complement depletion by Y-CVF significantly inhibited acute humoral allograft rejection in presensitized rats. As a therapeutic immunointervention tool for complement, Y-CVF has shown potential efficacy across ABO incompatible and positive cross-match barriers.     

sCR1sLe ameliorates ischemia/reperfusion injury in experimental lung transplantation

BACKGROUND: The nonspecific immune response with activation of the complement system and polymorphonuclear leukocytes is important for the mediation of reperfusion injury after lung transplantation. In this study, we investigated the combined blockade of the complement system and leukocyte adhesion by a novel drug combining soluble complement receptor type 1 (sCR1, CD35) with the selectin ligand sialyl Lewis X (sLe(X), CD15s) synthesized to sCR1sLe(X). Both sCR1 and sCR1sLe(X) were supplied by AVANT Immunotherapeutics, Inc, Needham, Massachusetts. METHODS: Orthotopic allogeneic single left lung transplantation was performed in male rats (Brown Norway to Fischer F344; n = 5 in all groups) after a total ischemic time of 20 hours. Recipients received either no specific treatment (control) or administration of sCR1 (10 mg/kg) or sCR1sLe(X) (10 mg/kg) 15 minutes before reperfusion by intracardiac injection. Twenty-four hours after reperfusion, the native contralateral lung was occluded to assess gas exchange of the graft only. In additional animals (5 per group), lung tissue was frozen 24 hours after reperfusion and assessed for myeloperoxidase activity as a measurement of neutrophil migration into the graft and thiobarbituric acid reactive substances to quantify lipid peroxidation. RESULTS: Graft function as assessed by arterial PO (2) in recipients treated with sCR1sLeX was superior not only to that of controls (383 +/- 53 vs 56 +/- 7 mm Hg, P =. 000095) but also to that of animals treated with sCR1 (243 +/- 45 mm Hg, P =.031). This improvement was confirmed by significant reduction of neutrophil migration (0.33 +/- 0.05 vs control, 1.0 +/- 0.09 DeltaOD/mg/min, P =.0000024) and lipid peroxidation (6.2 +/- 0. 38 vs control, 10.6 +/- 0.54 pmol/g, P =.00021). CONCLUSIONS: Our data indicate that combined inhibition of complement activation and leukocyte adhesion with sCR1sLe(X) reduces reperfusion injury significantly and that both mechanisms are effectively inhibited in this model.     

Increased risk of antibody-mediated rejection of reduced-size liver allografts

Because of the shortage of liver allografts in children, transplantation of reduced-size liver allografts from adult cadaveric donors or living, related donors is being done more frequently. Reduced-size liver allografts may be used in cases of ABO incompatibility and T-cell warm cross-match positivity. This experimental study in inbred rats was undertaken to determine if reduced-size liver allografts are more sensitive to antibody-mediated rejection than full-size liver allografts. Brown-Norway (BN) (RT1(n)) rats were sensitized by three successive skin grafts at 10-day intervals. Then orthotopic Lewis (LEW) (RT1(1)) liver grafts were transplanted into these BN rats. Full-size liver allografts were compared with reduced-size liver allografts (70% of donor liver). Control groups were composed of full-size and/or reduced-size isografts. Titers of specific antibodies were assayed using a complement-dependent assay before and after orthotopic liver transplantation. Histological and immunofluorescence studies (IgG, IgM, C(3), and fibrinogen deposits) were assessed. Recipients of reduced-size liver allografts died of hyperacute rejection at 36.6 +/- 4.1 h, significantly earlier than recipients receiving full-size liver allografts, which died of accelerated acute rejection at 259.2 +/- 25.2 h (P < 0.001). Either full-size or reduced-size isograft recipients survived indefinitely. A decrease in the titers of donor-specific antibodies was observed in both groups of animals. Slight deposits of IgG, IgM, C(3), and fibrinogen were observed in recipients of reduced-size liver allografts, whereas larger deposits were observed in recipients of full-size liver allografts. Our data demonstrate that there is an increased risk of antibody-mediated rejection of reduced-size liver allografts in sensitized recipients. This may have important clinical implications for partial liver grafting in cases of ABO incompatibility and T-cell warm cross-match positivity.     

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.     

Peritransplant streptavidin recipient treatment prolongs rat cardiac allograft survival

BACKGROUND: Because streptavidin shows high localization in inflamed tissues, it might also interfere with the proliferation of cells involved in allograft rejection. METHODS AND RESULTS: Treatment of na?ve ACI recipients with 20 mg/kg streptavidin i.p. alone significantly prolonged Lewis cardiac allografts from a mean survival time of 9.8+/-0.7 days in controls to 19.8+/-6.5 days, with one recipient accepting the graft permanently (>250 days). Peritransplant streptavidin treatment combined with 0.5 ml of antilymphocyte serum (ALS) transient immunosuppression led to permanent graft survival (>250 days) in 6 of 10 recipients. Second-set skin grafts performed 60 days after the primary cardiac allograft were prolonged to 45 days, whereas the third party Wistar-Furth (WF) skin grafts were rejected in 15 days without the rejection of the primary Lewis cardiac allografts. Pathology of transplanted cardiac allografts at 100 days showed no mononuclear cell infiltration or chronic allograft vasculopathy. Streptavidin given for 5 days at 20 mg/kg caused a moderate initial weight loss but had no effect on hematologic, biochemical, and histologic parameters in the treated recipients. CONCLUSION: This study demonstrates that peritransplant recipient treatment with streptavidin combined with peritransplant ALS induces prolonged cardiac and second-set skin allograft survival. We conclude that recipient peritransplant streptavidin treatment may provide a new strategy for the induction of transplant tolerance.     

Permanent rat cardiac allograft survival induced by ultraviolet B-irradiated donor lymphocytes and peritransplant cyclosporine

This study examines the effect of pretreatment with 10(8) ultraviolet B-irradiated donor leukocytes (UV-DL) with or without peritransplant cyclosporine (CyA) treatment (20 mg/kg on days 0, +1, and +2 relative to transplantation) on rat cardiac allograft survival across major histocompatibility loci. A single UV-DL pretreatment on day -3 or -7 (before transplantation) significantly prolonged survival of heart allografts from Wistar-Furth rats (W/F) in Lewis recipients from 6.8 +/- 0.8 days to 18.4 +/- 2.1 and 17.6 +/- 1.5 days (p less than 0.001), respectively. Multiple UV-DL infusions on days -14 and -7 increased the mean survival time to 20.0 +/- 0.9 days (p less than 0.001). Similarly, UV-DL infusion on day -3 or -7 significantly prolonged the mean survival time of heart allografts from ACI rats in Lewis rats. A single or multiple UV-DL infusions combined with peritransplant CyA led specifically to permanent W/F cardiac allograft survival (more than 200 days) in all recipients. Similarly, UV-DL infusion combined with peritransplant CyA led to indefinite survival of ACI cardiac allografts in two thirds of Lewis recipients. Adoptive transfer of splenocytes from long-term recipients of cardiac allografts, which specifically prolonged donor test grafts in syngeneic hosts, suggests that unresponsiveness to cardiac allografts is, in part, dependent on suppressor cells. This study emphasizes the importance of UV irradiation of DLs in the modulation of alloreactivity and the induction of donor-specific unresponsiveness in adult animals.     

免疫吸附预防高致敏肾移植受者超急性排斥反应

目的探讨免疫吸附对高致敏‘肾移植受者超急性排斥反应的预防作用。方法对10例群体反应抗体（PRA）〉40％的‘肾移植受者术前行免疫吸附治疗，观察其超急性排斥反应发生情况及不良反应。结果10例高致敏肾移植受者均未发生超急性排斥反应，仅有2例发生急性排斥反应，并通过免疫吸附及调整免疫抑制剂得到逆转。所有受者随访至今移植‘肾功能良好，未发生排斥反应。结论免疫吸附可以安全、有效地预防高致敏人群‘肾移植术后超急性排斥反应。     

Immunological studies in diabetic rat recipients with a pancreatic islet cell allograft in the brain

Intracerebrally (IC) transplanted outbred Wistar and inbred Lewis (AgB1/1) strain rat islets and pancreatic endocrine cells (PEC) were able to function for a prolonged period in nonimmunosuppressed diabetic inbred ACI (AgB4/4) rats across a major histocompatibility barrier. All recipients were sensitized to various degrees to the donor antigens, as demonstrated by circulating cytotoxic antibody, irrespective of the survival of the IC graft. Nevertheless, the antidonor antibody titers in the IC islet and PEC graft recipients were lower and peaked later when compared with ACI recipients that received an intraportal islet allograft. PEC were also transplanted IC in immunized ACI recipients. In recipients hyperimmunized by repeated splenocyte injections, accelerated PEC graft rejection was observed. In recipients with weaker immunization by intraportal whole islet allograft 2 months prior to the IC allograft, the IC PEC allografts were also rejected. To assess if ACI rats with long-term-functioning IC islet/PEC allograft developed tolerance to the donor antigens, these animals were transplanted with a donor-strain skin graft. The skin grafts were all rejected in a first-set fashion similar to normal control ACI rats. Also, 7/12 and 7/9 recipients rejected their functional IC islet or PEC allograft, respectively, following transplantation of a donor-strain skin allograft, thus indicating that the transplanted PEC maintained their antigenicity even after long-term survival of over 1 year in allogeneic recipients. The data indicate that the brain does possess immunoprotective properties for the islet/PEC allograft. The protection, however, is relatively weak and is possibly due to the paucity of the effector mechanism in the brain relative to that normally present systemically.     

Prolongation of discordant renal xenograft survival by depletion of complement. Comparative effects of systemically administered cobra venom factor and soluble complement receptor type 1 in a guinea-pig to rat model

Abstract There is an increasing body of evidence to suggest that inhibition of complement activation may be a valuable approach to avert hyperacute rejection. In our study, the guinea-pig to rat discordant kidney xenograft model was adapted for the investigation of renal transplant function and an attempt was made to delay the hyperacute rejection using systemically administered cobra venom factor (CVF) and soluble complement receptor type 1 (sCR1). The saline-treated control recipients experienced a rapid transplant rejection with a xenograft survival averaging 10.5 ± 2.1 min. Administration of a single 60 U/kg i. v. bolus of CVF significantly prolonged renal graft survival to 20.4 ± 2.5 h, and by a single bolus of sCR1 (50 mg/kg) a prolongation of graft survival to 18.8 ± 2.3 h was achieved. The grafts functioned only over periods of 2.5 ± 0.3 and 2.3 ± 0.2 h, respectively. No complications of sCR 1 were noted. We concluded that complement inhibition by sCR 1 may be an important component in the therapeutic approach aiming at the prevention of hyperacute rejection in human organ transplantation.     

Facial tissue allograft transplantation

A hemifacial allograft transplant model was used to investigate the rationale for development of functional tolerance across an MHC barrier. Thirty hemiface transplantations were performed in five groups of six Lewis (RT1(1)) rat recipients each. Isografts were performed in group 1. Transplants were obtained from semiallogenic LBN(RT1(1+n)) in group 2 and from fully allogenic ACI(RT1(a)) in group 3 donors, which served as allograft rejection controls. Group 4 grafts using LBN donors and group 5 using ACI donors in addition received CsA monotherapy (16 mg/kg/d for 1 week) and maintained at 2 mg/kg/d. Signs of graft rejection were sought daily. Isograft controls survived indefinitely. All nontreated allografts were rejected within 5 to 8 days posttransplant. Eighty-three percent of face-transplant recipients from LBN donors and 67% from ACI donors did not show any signs of rejection up to 270 days and 200 days, respectively. Flow cytometry at day 63 in LBN recipients showed the presence of donor-specific chimerism for MHC class I RT1(n) antigens, namely 3.39% CD4/RT1(n); 1.01% CD8/RT1(n) T-lymphocytes; and 3.54% CD45RA/RT1(n) B-lymphocytes. In ACI recipients the chimerism test revealed 10.55% CD4/RT1(a) and 4.59% of CD8/RT1(a) T-lymphocytes. MLR assay at day 160 posttransplant revealed suppressed responses against LBN donor antigens in group 4, but moderate reactivity to ACI donor antigens in group 5. Functional tolerance toward hemifacial allograft transplants induced across MHC barrier using a CsA monotherapy protocol was associated with the presence of donor-specific chimerism in T- and B-cell subpopulations.