Alloantibody and transferable suppressor activity induced by cyclosporine and blood transfusions in the rat

The effect of cyclosporine on the alloantibody response to blood transfusion was investigated in inbred strains of rats by IHA and CELISA; recipient animals differed from the donors at the class I (RT1A) or both class I and class II (RT1B) antigens of the major histocompatibility complex. Alloantibody titers stimulated in high responder PVGu/c animals by blood transfusions were attenuated by cyclosporine; this effect was not demonstrated in low responder PVGc rats, as alloantibody titers decreased after further blood transfusions whether or not cyclosporine was given. Cyclosporine not only reduced the initial IgM response but suppressed the subsequent production of IgG. Splenocytes from rats receiving cyclosporine and blood transfusions from donors that differed from the recipients at the class I antigen were effective in suppressing the subsequent antibody response to blood transfusion. When blood transfusions from donors which differed from the recipients at both class I and class II antigenic loci were given after splenocyte transfer, a greater degree of immunosuppression was detected than if the transfusion donor differed only at the class I locus. These data suggest that the sensitization produced by blood transfusions and the persistence or decline of the alloantibody response depend upon the responder status of the recipient. Blood transfusions given with cyclosporine are capable of inducing suppressor activity that is transferable in spleen homogenates. Subsequent alloantibody responses are influenced by the class I and class II disparities of the donor and recipient animals. If these results can be extrapolated to clinical practice, cyclosporine should be given with pretransplant blood transfusions to prevent sensitization, and the transfusion donor should differ from the recipient at both class I and class II antigenic loci.     

Suppressor T cells in rats with prolonged cardiac allograft survival after treatment with cyclosporine

DA rats treated with cyclosporine for 2 weeks after being grafted with an RT1-incompatible PVG heart graft did not reject the graft and developed a state of specific unresponsiveness to graft antigens. The cellular mechanisms maintaining this state of unresponsiveness were studied by testing the capacity of lymphocytes from these animals to effect or inhibit graft rejection in irradiated grafted hosts. Whole lymph node and spleen cell populations, and the T cell subpopulation separated from the latter, failed to restore the rejection of PVG hearts in irradiated DA recipients but restored third-party Wistar-Furth (W/F) rejection. Both whole spleen cells and the splenic T cell subpopulation had the capacity to suppress the ability of normal DA lymphocytes to cause graft rejection. Suppression was not dependent upon a state of chimerism in grafted cyclosporine -treated animals, and was not associated with any measurable alterations in the proportion of cytotoxic/suppressor T cells in lymphoid tissues. These studies show that the state of specific unresponsiveness that follows the treatment of heart grafted rats with cyclosporine is dependent, in part, upon active suppression that is induced or mediated by T lymphocytes. Many features of the immune reactivity of cyclosporine -treated grafted rats support the hypothesis that the mechanism of specific suppression in these animals is akin to that of enhancement, rather than to that of transplantation tolerance induced in neonatal rats.     

Pretransplant transfusions in cardiac allograft recipients

The role of pretransplant transfusion in cardiac allograft recipients was determined retrospectively in 68 patients. Three groups were studied: group 1 (n = 29) received no pretransplant transfusion, group 2 (n = 15) received transfusion over one year prior to transplantation, and Group 3 (n = 24) received 5 or 10 50-100 ml units of random donor red blood cells or buffy coat 2-4 weeks prior to transplantation. Data were analyzed for survival, number of rejection episodes, and number of infections. Immunosuppression included azathioprine, prednisone, and antithymocyte globulin. Survival in transfused patients (groups 2 and 3) was 68% and 51% at 1 and 5 years, respectively, while in the nontransfused population (group 1) it was 35% and 16%. The incidence of rejection episodes per year of survival was similar in the three groups (group 1: 1.3, group 2: 1.1, group 3: 1.3; P greater than 0.05). The number of infections per year of survival were greater in the transfused patients but this did not achieve statistical significance (group 1: 1.0, group 2: 1.2, group 3: 1.7; P greater than 0.05). Thus, we conclude that cardiac transplant recipients who have received blood transfusions prior to transplantation may have enhanced survival over patients who have not received preoperative transfusions.     

Alloreactive T suppressor cells in the rat. I. Evidence of three distinct subsets of splenic suppressor T cells resistant to cyclosporine

In this study we examined the effect of cyclosporine on three distinct subsets of T suppressor (Ts) cells identified in a rat renal allograft model. Ts inducer (Ts1) cells having the CD4 marker are found in the spleens of DA rats undergoing acute rejection of LEW kidneys. Transducer (Ts2) and effector (Ts3) cells both carry the CD8 marker and are found in the spleens of long-term surviving DA rats bearing LEW kidney allografts made tolerant by donor-specific blood transfusions or by cyclosporine (in most cases). These latter cells are distinguished by their susceptibility to cyclophosphamide (CY), Ts2 cells being resistant while Ts3 cells are sensitive to CY. When Ts cells from DA rats undergoing acute graft rejection of LEW kidneys or bearing long-term-surviving LEW kidneys that had been treated with cyclosporine (10mg/kg/day) for 2 or 10 days, respectively, were adoptively transferred into lightly irradiated DA recipients, these cells were still able to specifically induce long-term survival of LEW kidneys. LEW kidney survival was not prolonged in DA rats given no cells or cells from rats treated with cyclosporine for 10 days. Thus it would appear that the three functional subsets of Ts cells demonstrated in this renal allograft model by adoptive transfer of spleen lymphocytes are not inhibited by cyclosporine, suggesting that this resistance of Ts cells to cyclosporine may be partly responsible for the immunosuppressive effect of this agent.     

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.     

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.     

Blood transfusions, suppressor T cells, and renal transplant survival

Fifteen men undergoing chronic hemodialysis were transfused with 2 units of packed red cells, none of these patients having been previously transfused. They were studied before and after transfusion to determine suppressor T cell numbers and activity, and to monitor the appearance of cytotoxic antibodies. Although the number of suppressor T cells did not change, their function was significantly increased three weeks after the transfusion. This had largely returned to normal by 20 weeks. No cytotoxic antibodies were produced. Twelve of the patients subsequently received cadaveric renal transplants and nine of these kidneys are currently functioning more than a year after transplantation. Although the blood transfusions may have helped to produce these satisfactory results, it is accepted that the nonspecific increase in suppressor cell function may not have been the only mediator because this activity had returned to normal in most cases by the time the patients were transplanted.     

PUVA augments cyclosporine A-mediated rat cardiac allograft survival.

PUVA, the administration of the photosensitizer 8-methoxypsoralen (8-MOP) followed by exposure of the skin to longwave ultraviolet radiation (UVA, 320-400 nm), is employed clinically for the treatment of skin diseases. PUVA is immunosuppressive and we have shown previously that it can significantly prolong skin allograft survival. This enhanced survival is associated with reduced spleen cell cytotoxic activity against donor cell targets with preserved ability of treated animals to be immunized to third-party alloantigens 5 days after exposure to a course of PUVA. To examine whether PUVA may potentiate the effect of cyclosporine A (CYA) in inhibiting cardiac allograft rejection, we employed a rat cardiac transplant model. Lewis rats (RT1(1) received cardiac allografts at a heterotopic site from Lewis Brown Norwegian (RT1(1/n)) hybrid donors. Seventy animals were equally divided into 10 groups. Starting on the day of surgery, three groups received a suboptimal doses of CYA (1.5, 4.5, or 9.0 mg/kg im), three groups received the same doses of CYA and 1.0 mg/kg of 8-MOP injected ip followed by 6.35 J/cm2 of UVA radiation to their shaved dorsums (PUVA), one group received PUVA alone, one group received UVA radiation alone, one group received 8-MOP alone, and the final group received no treatment. Therapy was carried out daily for 7 days and survival of the allograft was assessed by daily palpation of the transplanted heart.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prolongation of cardiac allograft survival in rats by anti-TNF and cyclosporine combination therapy.

Cyclosporine is well known to have many adverse side effects. However, while decreasing the dosage of CsA can reduce its toxicity, this also lowers its immunosuppressive effectiveness. Additionally, anti-tumor necrosis factor has been demonstrated to have immunosuppressive activity and been shown to prolong cardiac allograft survival. This current study therefore investigated the efficacy of a combined therapy of anti-TNF with low-dose CsA in a rat heterotopic cardiac transplant model utilizing Brown-Norway donors and Lewis recipients. Control transplant recipients received no immunotherapy. Experimental animals received single-dose anti-TNF intraperitoneally on posttransplant days 0, 3, or 5 and/or low-dose CsA (1.5 mg/kg/day) intramuscularly from days 0 to 14 after transplantation. Rejection was determined by the lack of contractions in the transplanted heart. No animal received any other form of immunosuppression. Graft survival was significantly prolonged with combination CsA and anti-TNF therapy, suggesting a synergistic effect against acute cardiac allograft rejection, possibly from CsA and anti-TNF interacting at different levels of the recipient immune response. This form of combination therapy may hold promise for future immunosuppressive techniques.     

Combination thalidomide and cyclosporine for cardiac allograft rejection. Comparison with combination methylprednisolone and cyclosporine

Combination CsA with corticosteroids is the most commonly used maintenance immunosuppressive regimen after cardiac transplantation, although their high-toxicity profiles frequently limit their clinical benefit. Immunosuppressive agents that would act synergistically with CsA but without the toxicity profile of corticosteroids would be clinically useful. Thalidomide was removed from the market due to its teratogenic effects, although it has known immunomodulatory activity. The purpose of this study was (1) to determine whether maintenance immunosuppression with thalidomide and subtherapeutic doses of CsA can help prevent rat cardiac allograft rejection; and (2) to compare its synergism with CsA to the commonly used corticosteroid, methylprednisolone. ACI-LEW allografts were all treated with subtherapeutic doses of CsA (10 mg/g/day, s.c.) for 4 days. When CsA was then discontinued, severe rejection developed by posttransplant day 14. Group 1 received CsA alone. Group 2 received in addition oral thalidomide 100 mg/day for 14 days. Groups 3, 4, and 5 received CsA and methylprednisolone (low dose: 0.2 mg/kg/day s.c.; moderate dose: 2.0 mg/kg/day s.c.; and high dose: 20 mg/kg/day s.c. Twelve histologic parameters of rejection were semiquantitatively graded 0-4, and total pathology scores were determined. The combination of thalidomide and subtherapeutic CsA significantly reduced the severity of myocardial necrosis, interstitial inflammation, interstitial edema, and the total pathology score. Thalidomide was found to be equally as effective as low-, moderate-, and high-dose methylprednisolone. The results of this study suggest the potential clinical role of CsA and thalidomide in maintenance immunosuppressive regimens, thereby avoiding the use of corticosteroids.     

Effects of pre- and postengraftment donor-specific transfusions and cyclosporine on the enhancement of experimental allograft survival.

The tolerogenic effects of immediate pretransplant donor-specific transfusion (DST) with cyclosporine (CsA) have been well described. The purpose of this study was to determine if these effects could be improved upon by the administration of post-transplant DSTs. When added to a 29-day course of CsA, a single DST given 24 hr pretransplant improved graft survival compared to CsA alone (84.9 +/- 12.3 vs 40.0 +/- 8.8 days; P less than 0.05). The administration of an additional DST on post-transplant Days 7, 14, and 21 further improved this survival to 152 +/- 28 days, with 45% of grafts surviving greater than 200 days, until sacrifice. The donor specificity of this effect was demonstrated by the increased survival of second ACI grafts transplanted into Lewis recipients with existing "tolerant" ACI allografts (long-term survivors, or LTS); third-party Buffalo rat hearts transplanted into LTS rats in a similar manner were rejected normally. Loss of graft antigenicity was not seen, as retransplanted ACI hearts obtained from LTS Lewis rats were rejected in a first-order manner. From this we conclude that (1) the addition of multiple post-transplant DSTs improve the enhancement seen with preoperative DST and CsA, (2) loss of graft antigenicity does not contribute to this improved enhancement, and (3) this effect appears to be donor antigen specific.