Prolonged Heart Allograft Survival Research Articles

Arsenic trioxide is a novel agent for combination therapy to prolong heart allograft survival in allo-primed T cells transferred mice

Alloreactive memory T cells are major barriers to transplantation acceptance due to their capacity to accelerate rejection. Here, we investigated the effects of combined treatment with arsenic trioxide (As2O3) and blocking monoclonal antibodies (mAb) against CD154 and LFA-1 (anti-CD154/LFA-1) on graft survival as well as changes in pathology and immunological responses in mice with adoptively transferred allo-primed T cells. The mean survival time (MST) for the cardiac allografts in recipient mice receiving the combination of As2O3 and anti-CD154/LFA-1 was significantly longer (>113.7days) compared to those receiving anti-CD154/LFA-1 (23.2days), As2O3 (12.5days) alone or no treatment (5.5days). This combined strategy distinctly inhibited lymphocyte infiltration in grafts, proliferation of splenic T cells and the generation of memory T cells in spleens. Moreover, the combined treatment caused the significant down-regulation of IL-2 and IFN-γ accompanied by increased expression of TGF-β and regulatory T cells (Tregs) in spleens, which led to long-term cardiac allograft survival in recipient mice. These results highlight the potential application of As2O3 and its contribution in combination therapy with antibody blockade to delay rejection by memory T cells.

CCR5 Blockade in Combination with Cyclosporine Increased Cardiac Graft Survival and Generated Alternatively Activated Macrophages in Primates

Maraviroc (MVC), a specific antagonist of CCR5 expressed on macrophages and activated T cells, may modulate inflammation and may be useful in patients with HIV infection. In this study we used nonhuman primates to examine the effect and mechanism of MVC alone or in combination with cyclosporine (CsA) to prolong cardiac allograft survivals. In an established rhesus monkey cardiac allograft model, recipients treated with MVC plus CsA showed significantly prolonged survival of heart allografts (>240 d, p < 0.001). These in vivo results in the MVC/CsA group correlated with delayed alloantibody response and markedly decreased graft infiltration by CCR5(+), CD4(+), CD8(+), and CD68(+) cells (p < 0.05), as compared with other groups. Furthermore, grafts from the MVC/CsA group had elevated numbers of alternatively activated macrophages (AAMs) and the expression of peroxisome proliferator-activated receptor γ (PPARγ). Blockade of PPARγ abrogated the prolonged allograft survival (median survival time, 45 d) and the upregulated AAMs in MVC/CsA-treated recipients. In conclusion, MVC/CsA protects cardiac allograft in primates and this effect is associated with generating AAMs through activation of the PPARγ nuclear receptor.

Endogenous dendritic cells mediate the effects of intravenously injected therapeutic immunosuppressive dendritic cells in transplantation

AbstractThe prevailing idea regarding the mechanism(s) by which therapeutic immunosuppressive dendritic cells (DCs) restrain alloimmunity is based on the concept that they interact directly with antidonor T cells, inducing anergy, deletion, and/or regulation. However, this idea has not been tested in vivo. Using prototypic in vitro–generated maturation-resistant (MR) DCs, we demonstrate that once MR-DCs carrying donor antigen (Ag) are administered intravenously, they decrease the direct and indirect pathway T-cell responses and prolong heart allograft survival but fail to directly regulate T cells in vivo. Rather, injected MR-DCs are short-lived and reprocessed by recipient DCs for presentation to indirect pathway CD4+ T cells, resulting in abortive activation and deletion without detrimental effect on the number of indirect CD4+ FoxP3+ T cells, thus increasing the regulatory to effector T cell relative percentage. The effect on the antidonor response was independent of the method used to generate therapeutic DCs or their viability; and in accordance with the idea that recipient Ag-presenting cells mediate the effects of therapeutic DCs in transplantation, prolongation of allograft survival was achieved using donor apoptotic MR-DCs or those lacking surface major histocompatibility complex molecules. We therefore conclude that therapeutic DCs function as Ag-transporting cells rather than Ag-presenting cells to prolong allograft survival.

296 Macrophage migration in tolerance

Active-targeted delivery to lymph nodes represents a major advance toward more effective treatment of immune-mediated disease. The MECA79 antibody recognizes peripheral node addressin molecules expressed by high endothelial venules of lymph nodes. By mimicking lymphocyte trafficking to the lymph nodes, we have engineered MECA79-coated microparticles containing an immunosuppressive medication, tacrolimus. Following intravenous administration, MECA79-bearing particles showed marked accumulation in the draining lymph nodes of transplanted animals. Using an allograft heart transplant model, we show that targeted lymph node delivery of microparticles containing tacrolimus can prolong heart allograft survival with negligible changes in tacrolimus serum level. Using MECA79 conjugation, we have demonstrated targeted delivery of tacrolimus to the lymph nodes following systemic administration, with the capacity for immune modulation in vivo.

Interleukin 7 receptor α as a potential therapeutic target in transplantation

Drugs targeting memory lymphocytes may allow for a better control of rejection in transplantation, particularly in immunized patients. In this article the rationale of targeting interleukin 7 receptor alpha (IL-7Ralpha), a molecule expressed by both memory and naive T cells, is reviewed in the context of transplantation. Whereas naive T cells are partly responsible for acute rejection and are targeted by current immunosuppressive drugs that block costimulatory signals (cyclosporine A, anti-CD3 antibody, anti-CD52 antibody, anti-thymocyte globulin, etc.), memory T cells are resistant to costimulation blockade. As such, memory cells are an obstacle to experimental tolerance induction and may be involved in chronic rejection. There is thus much scientific interest in developing molecules able to target these cells. The role of the IL-7/IL-7Ralpha pathway in transplantation rejection has been suggested by the effect of an anti-IL-7 monoclonal antibody which, when associated with costimulation blockade, prolonged heart allograft survival in mice. Here the hypothesis that targeting IL-7Ralpha would preserve effector T cells that are less dependent on IL-7 for survival while sparing regulatory CD4+ CD25high IL-7Ralpha(low) T cells is discussed. An anti-IL-7Ralpha antibody could also help achieve allograft tolerance by reducing alloreactive cells.

Increased CD4 +CD25 +Foxp3 + regulatory T cells in tolerance induced by portal venous injection

A portal vein injection (PVI) of allogeneic donor antigen is known to prolong the survival of a subsequently transplanted allograft; however, the underlying mechanism remains to be clarified. Irradiated C57BL/6 (B6) splenocytes were injected into BALB/c mice via the portal vein. Seven days after injection, the proportions of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells were determined in the blood, liver, and spleen. CD4(+) and CD8(+) T cells were isolated from BALB/c mice that received PVI of B6 splenocytes (PVI mice), adoptively transferred into recipient BALB/c mice 1 day before B6 or third-party C3H heart transplantation, and graft survival was compared. B6 or C3H heart allografts were implanted into anti-CD25 monoclonal antibody (mAb)-treated PVI and untreated PVI mice, and graft survivals were compared. The percentages of CD4(+)CD25(+)Foxp3(+) Treg, cytokine profiles, and ratios of apoptosis were determined in anti-CD25 mAb-treated PVI and untreated PVI mice. PVI of allogeneic cells induced antigen-specific tolerance and increased the percentage of CD4(+)CD25(+)Foxp3(+) Treg. Adoptive transfer of CD4(+) T cells, but not CD8(+) T cells, from PVI mice prolonged B6 heart allograft survival. Depletion of CD4(+)CD25(+) T cells prevented the induction of tolerance and decreased the percentage of CD4(+)CD25(+)Foxp3(+) Treg in the CD3(+) T-cell pool, and thus was associated with decreased production of interleukin (IL)-4 and apoptosis of T cells. Increased CD4(+)CD25(+)Foxp3(+) Treg play an important role in portal vein tolerance induction, at least partly via increasing the production of IL-4 and decreasing apoptosis of T cells.

The PD-L1 Signal is Important to Liver Dendritic Cells in Induction of Foxp3+CD4+CD25+ Treg and Liver Transplant Tolerance (141.33)

Abstract Our previous studies have demonstrated that Foxp3+CD25+CD4+ regulatory T cells (Treg) play an important role in the induction of murine liver spontaneous transplant tolerance. How Treg are induced and what their mechanisms are in the regulation of liver transplant tolerance remain undefined. Here, we investigated the role of liver dendritic cells (DCs) on the induction of Treg and liver graft tolerance in vivo and in vitro. Fms-like tyrosine kinase 3 ligand (Flt3L) mutation mice, which have severe reduction in all types of DCs, and PD-L1 deficient mice were used to examine the role of liver DCs and the PD-L1 signal in Treg induction and liver transplant tolerance. Our results showed that liver DCs, which expressed a high number of PD-L1 molecules, induced more Foxp3+CD25+CD4+ Treg in vitro compared to spleen DCs. However, DCs from PD-L1 deficient mice failed to expand Foxp3+CD25+CD4+ Treg in vitro. Adoptive transfer of Foxp3+CD25+CD4+ Treg expanded from liver DCs prolonged heart allograft survival significantly more than in the CD4 treated controls. The liver grafts from Flt3L-/- and PD-L1-/- mice were rejected acutely in the C3H recipients. Foxp3+ cells were reduced, but IL-2, IL-10, and IFN-γ producing cells were significantly increased in the liver graft and recipient spleen sections of Flt3L-/- and PD-L1-/- donors. Thus, liver DCs play a critical role in the induction of Treg, which underpin spontaneous acceptance of liver allografts. The function of DCs on Treg induction appears to depend on the PD-L1 signal.

Combined therapy of CD4 +CD25 + regulatory T cells with low-dose sirolimus, but not calcineurin inhibitors, preserves suppressive function of regulatory T cells and prolongs allograft survival in mice

Our previous study proved that sirolimus is a potent immunosuppressant which induces long-term allograft survival depends on persistence of alloantigens. CD4 +CD25 + regulatory T (Treg) cells are potent suppressors in transplantation. Our objectives focus on whether combined-therapy of Tregs with immunosuppressants could prolong allograft survival in mice. The study showed that inhibition of Tregs was maintained by co-cultured with sirolimus (1 nM) in vitro, but not tacrolimus (1 nM) or CsA (1 nM). When the concentration was increased > 100 nM, suppression was fallen. Based on the ability of sirolimus to target effector T cells, but retaining the inhibition of Tregs, an adoptive infusion of donor alloantigen specific Tregs combined with 30-day sirolimus (1 mg/kg) and 3-day ATG (20 mg/kg) was found to prolong heart allograft survival in mice. Even though the cell numbers of CD4 + T cells were found to decrease in sirolimus-treated mice, sirolimus selectively enhanced the numbers of CD4 +CD25 + cells and increased the expression of Foxp3 in spleens and lymph nodes, respectively, in recipients. However, combined therapy with low-dose CsA (5 mg/kg) or tacrolimus (1 mg/kg) reduced significantly the expression of Foxp3 and failed to prolong the allograft survival. In summary, expanded Tregs exposed to sirolimus can survive, proliferate, and preserve inhibition in vitro. Tregs are more resistant to sirolimus than other T cells. Combined with Tregs, sirolimus rather than calcineurin inhibitors, prolongs the allograft survival. Sirolimus may be the best copartner for Tregs therapy. It also suggests calcineurin-dependent signals may be required in the development of Tregs.

Protosappanin A, an Immunosuppressive Constituent From a Chinese Herb, Prolongs Graft Survival and Attenuates Acute Rejection in Rat Heart Allografts

Objective Caesalpinia sappan L., which has been used in oriental medicine as an analgesic and antiinflammatory agent, has shown immunosuppressive activity on acute rejection on rat heart allografts. The present study was designed to investigate the potency of protosappanin A, one major ingredient of C. sappan L., in rat heart transplantation. Materials and Methods Protosappanin A isolated from an ethanol extract of C. sappan L. was identified by wave spectrum. All groups consisted of Wistar donors into Sprague-Dawley (SD) recipients, including large (25 mg/kg) or small (5 mg/kg) doses of protosappanin A plus cyclosporine (10 mg/kg). A control group was used. Animals were given the drugs on postoperative day 2. We observed graft survival and pathologic conditions of the hearts. Blood samples were obtained on postoperative day 7 to measure the CD4+/CD8+ T-cell ratio. Graft perforin and granzyme B mRNA expression levels were examined with reverse transcription-polymerase chain reaction (RT-PCR) methods. Results Protosappanin A or cyclosporine significantly prolonged heart allograft survival ( P < .01), alleviated myocardial pathologic damages ( P < .01), decreased the CD4+/CD8+ ratio ( P < .05), and inhibited perforin and granzyme B mRNA expressions in the graft ( P < .05). Conclusions These findings demonstrated that protosappanin A prolonged heart allograft survival by significantly attenuating acute rejection.

Prolongation of heart allograft survival after long-term expression of soluble MHC class I antigens and vIL-10 in the liver by AAV-plasmid-mediated gene transfer

The essential prerequisite for successful gene therapy in vivo is an effective and long-lasting transfer of the desired gene into the respective cell type or tissue. Over the last decades, many different methods have been developed for this purpose. The use of plasmid DNA seems to be a good alternative to the commonly used viral vectors because its large-scale production is simple, and side effects are low. Unfortunately, most reports describe only short-term expression in vivo, probably due to the lack of genomic integration in the target cell. This problem can possibly be addressed by the use of adeno-associated virus plasmids (AAV plasmids), where the coding sequences are cloned between the AAV-specific inverted terminal repeats. Here, we report our results after allogeneic heart transplantation, which followed AAV-plasmid-mediated gene transfer of the rat soluble major histocompatibility complex class I antigen RT1.A(a) and viral interleukin (vIL)-10 in the "high"-responder Dark Agouti to Lewis rat strain combination. A high and stable long-term expression was achieved by in vivo transfection of the liver using AAV plasmids. Serum levels over 1,000 ng/ml of soluble RT1.A(a) and over 300 pg of vIL-10, respectively, were achieved. Expression levels remained high for up to several months. A mean prolongation of heart allograft survival of 1 to 2 days was demonstrated after transfection of either RT1.A(a) or vIL-10.

Inhibition of Heart Allograft Rejection With Mitomycin C???Treated Donor Dendritic Cells

We showed previously that dendritic cells (DCs) treated with mitomycin C (MMC) tolerize allogeneic T cells in vitro and this might be mediated by downregulation of CD80, CD86, and ICAM-1. Here we analyze the suppression of the T-cell response induced by MMC-DCs in vivo. Rats injected with allogeneic DCs developed a strong lymph node reaction, whereas MMC-DCs induced no reaction. The same effect was obtained when CD80, CD86, and ICAM-1 expressed by DCs were blocked with antibodies. One injection of donor MMC-DCs strongly prolonged heart allograft survival in a donor-specific manner. Suppression of rejection was also achieved when donor DCs were pretreated with a combination of anti-CD80, anti-CD86, and anti-ICAM-1 antibodies, showing that downregulation of these molecules confers the DCs inhibitory properties. We conclude that allogeneic MMC-DCs specifically inhibit the T-cell response in vivo and that downregulation of CD80, CD86, and ICAM-1 is a potential mechanism of this effect.

Impact of vaccine therapy using nuclear histone H1 on allograft survival in experimental organ transplantation

Background We recently reported that autoreactive antibody (Ab) against nuclear histone H1 had been identified as an immunosuppressive factor in a rat tolerogenic orthotopic liver transplantation (OLT) model. The present study aimed to determine whether the up-regulation of antihistone H1 Ab by histone H1 vaccination leads to tolerance. Methods Histone H1-immunized rats were established by intraperitoneal vaccination with histone H1 at every two-weekly interval. By using mixed lymphocyte reaction (MLR) and heterotopic heart transplantation (HHT), the alloreactive T cell response and allograft survival of histone H1-immunized rats were compared with those of control rats. Cytokine and cellular profiles in histone H1-immunized rats were determined by reverse transcriptase polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Results Immunization with histone H1 in Freund's adjuvant induced alloreactive T cell unresponsiveness and prolonged heterotopic heart allograft survival. It also down-regulated the expression of major histocompatibility complex (MHC) class II and CD25 on splenic cells, elevated the T helper cell type 2 (Th2) skewing index (Interleukin (IL)-4/interferon (IFN)-γ ratio or IL-4/IL-2 ratio) and modified the serum cytokine profiles. Conclusions The present results suggest that histone H1 vaccination of transplant recipients, which leads to the production of immunosuppressive factor and the modification of the cytokine/cellular profiles, has great potential as a tolerance therapy for prospective transplantation.

Administration of dendritic cells modified by RNA interference prolongs cardiac allograft survival

Systemic administration of immature donor-dendritic cells (DC) that are deficient in co-stimulatory molecules delays the onset of allograft rejection. However, it is not easy to control culture condition and guarantee that the administered DC are in the immature stages, which obviously affects their therapeutic effect. In this study, we attempted to inhibit expression of CD86 on DC using an RNA interference technology. The function of CD86(low) DC was determined by the influence on their capacity to stimulate T cell proliferation and by the effect of DC systemic administration on survival of cardiac allografts. CD86(low) DC stimulated low T cell proliferative responses in vitro and administration of CD86(low) DC prolonged survival of heart allografts in vivo. These results suggest that RNA interference is a useful approach to modify DC function, which has potentials for clinical application.

TIRC7 is induced in rejected human kidneys and anti-TIRC7 mAb with FK506 prolongs survival of kidney allografts in rats

TIRC7 delivers essential signals during immune activation as antibodies targeting TIRC7 inhibit lymphocyte proliferation and Th1 cytokine expression in vitro and prolonged kidney and heart allograft survival in vivo. Immunohistochemical analysis of biopsy specimens from human renal allografts undergoing rejection despite treatment with Calcineurin inhibitors (CI) showed elevated TIRC7 expression. Accordingly, with a view to clinical application, we evaluated the therapeutic effect of a chimerized anti-TIRC7 mAb in combination with Tacrolimus (FK506) using a rat kidney transplantation model (DA to Lewis). The combination of sub-therapeutic doses of both compounds significantly ( p < 0.05) prolonged the median graft survival to 19.5 days compared to monotherapy with FK506 (median survival, 7d) or mAb against TIRC7 (7d). These results suggest a potential synergism of anti-TIRC7 mAb and FK506 action, which could be developed into a novel combination therapy in the clinic by lowering side effects of present CI treatment. Moreover, the identification of TIRC7 in graft infiltrating lymphocytes might serve as a diagnostic marker to detect allograft rejection.

Induction of endotoxin tolerance inhibits alloimmune responses

It was recently reported that the induction of endotoxin tolerance (ET), which is defined as a reduced response to a lipopolysaccharide (LPS) challenge following the first LPS encounter, inhibits major histocompatibility complex (MHC)-restricted antigen presentation. This raises the question whether alloimmune responses can be inhibited by inducing ET in transplant donors. C57BL/6 mice were treated with a low dose of LPS prior to a challenge with a high dose of LPS to induce ET. Hearts from endotoxin-tolerized C57BL/6 mice were transplanted to BALB/c mice. The survival of the endotoxin-tolerized heart allografts was significantly prolonged. By using irradiated splenocytes from C57BL/6 mice and allogeneic splenocytes from BALB/c mice, a mixed lymphocyte reaction (MLR) assay was performed. The MLR assay used CFSE, and revealed that the splenocytes from the endotoxin-tolerized mice failed to induce the proliferation of allogeneic CD4 + and CD8 + T cells. Cytokine analyses of the supernatant of the MLR culture using endotoxin-tolerized stimulators revealed a distinct shift in the Th 1/Th 2 balance toward the Th 2-type response. The induction of ET increased the proportion of myeloid-related dendritic cells (DCs) expressing molecules necessary for antigen presentation, which favor the development of a Th 2 response; however, it reduced the proportion of lymphoid-related DCs expressing those molecules, which favor the development of the Th 1 response. Although the relevance of these findings with regard to the prolonged survival of the endotoxin-tolerized heart allografts remains to be elucidated, this is the first study to demonstrate that the induction of ET in donor animals inhibits alloimmune responses.

Induction of Tolerance by Exosomes and Short-Term Immunosuppression in a Fully MHC-Mismatched Rat Cardiac Allograft Model

Exosomes are MHC-bearing vesicles secreted by a wide array of cells. We have previously shown that donor-haplotype exosomes from bone marrow dendritic cells (DCs) injected before transplantation significantly prolong heart allograft survival in congenic and fully MHC-mismatched Lewis rats. Here we show that donor exosomes administered after transplantation are similarly able to prolong allograft survival, however, without inducing tolerance. We therefore tested the effect of exosomes combined with short-term LF 15-0195 (LF) treatment, which blocks the maturation of DCs, so that donor-MHC antigens from exosomes could be presented in a more tolerogenic environment. LF treatment does not preclude the development of a strong antidonor cellular response, and while LF, but not exosome, treatment inhibits the antidonor humoral response and decreases leukocyte graft infiltration, allografts from LF-treated recipients were either acutely or strongly chronically rejected. Interestingly, when combined with LF treatment, exosomes induced a donor-specific allograft tolerance characterized by a strong inhibition of the antidonor proliferative response. This donor-specific tolerance was transferable to naïve allograft recipients. Moreover, exosomes/LF treatment prevented or considerably delayed the appearance of chronic rejection. These results suggest that under LF treatment, presentation of donor-MHC antigens (from exosomes) can induce regulatory responses that are able to modulate allograft rejection and to induce donor-specific allograft tolerance.

Enhancement of NKT Cells and Increase in Regulatory T Cells Results in Improved Allograft Survival

Natural killer T (NKT) cells can serve as regulatory cells important in peripheral tolerance. In an experimental colitis model, it was shown that FK506 enhances the tolerizing effect of regulatory NKT cells induced by oral tolerance. We explored whether a subtherapeutic dose of FK506 could enhance the tolerizing effect of NKT cells induced by oral administration of donor spleen cells (SCs) in the pre-transplant period to prolong heart allograft survival. Heterotopic heart transplantation was performed from BALB/c to B6 mice. The B6 recipients were pre-treated with either BALB/c SCs (2 x 10(7)/mouse), or FK506 (1.0 mg/kg/d), or BALB/c SCs + FK506 by gavage every other day for a total of five feedings before transplantation. Heart allograft survival was only significantly prolonged in the BALB/c SC + FK506 pre-fed mice. This was associated with a marked increase of NKT cells in both the liver and spleen of the recipients, and most importantly, 7 days after transplantation, an increase in CD25+CD4+ T cells expressing CTLA4 in the spleen. In our model it appears that a subtherapeutic dose of FK506 enhanced the tolerizing effect of NKT cells induced by oral tolerance, prolonging allograft survival by generating CD25+CD4+ CTLA4 T cells. This appears to be an excellent in vivo model to generate regulatory T cells to allospecific transplant antigens.

Enhancement of NKT cells increases regulatory T cells, resulting in improved allograft survival

Natural killer T (NKT) cells can serve as regulatory cells important in peripheral tolerance. In an experimental colitis model, it was shown that FK506 enhances the tolerizing effect of regulatory NKT cells induced by oral tolerance. We explored whether FK506 could enhance NKT cells induced by oral administration of donor spleen cells (SCs) to prolong heart allograft survival. Methods: Heterotopic heart transplantation was performed from BALB/c to B6 mice. The B6 recipients were pre-treated with either FK506 (1.0mg/kg/d), or BALB/c SCs (2×10∧7/mouse), or FK506 + BALB/c SCs by gavage every other day for a total of 5 feedings prior to transplantation.

Heart Allograft Protection with Low-Dose Carbon Monoxide Inhalation: Effects on Inflammatory Mediators and Alloreactive T-cell Responses

Carbon monoxide (CO), a byproduct of heme catalysis, has lately received considerable attention as a regulatory molecule in cellular and biological processes. CO has been shown to provide potent protection against a variety of tissue injuries. We hypothesized in this study that low concentration CO would be beneficial for organ allografts, which frequently undergo several types of injury such as ischemia/reperfusion, alloimmune reaction, and inflammation The efficacy of low-dose CO was examined in a fully allogeneic LEW to BN rat heterotopic heart transplantation (HHTx) model. Recipients were kept in air or exposed to low-dose CO (20 ppm) for 14, 28, or 100 days after HHTx under short-course tacrolimus CO treatment (d0-28, 0-100) was remarkably effective in prolonging heart allograft survival to a median of >100 from 45 days in the air-control group, with significant reductions of arteritis, fibrosis, and cellular infiltration, including macrophages and T cells. CO inhibited intragraft upregulation of Th1 type cytokines (IL-2, IFNgamma), proinflammatory mediators (IL-1beta, TNFalpha, IL-6, COX-2), and adhesion molecule. Shorter CO exposure in early (0-13d) and late (14-28d) posttransplant periods also prolonged graft survival, with a significant inhibition of inflammatory mediators These results show that low dose CO inhalation protects heart allografts and can considerably prolong their survival. CO appears to function via multiple mechanisms, including direct inhibition of Th1 type cytokine production and regulation of inflammatory responses.

Effect of FTY720 and ICAM-1 mAb mono and combination therapy in cardiac allo-transplantation in rats

Objective To observe the effect of FTY720 and ICAM-1 mAb mono and combination therapy in cardiac allo-transplantation in rats. Methods Rats were randomly assigned to 9 groups, heart allo-transplantation were performed in abdominal site with micro-surgical technique. Recipients with allografts were treated with different doses of FTY720 and (or) ICAM-1 mAb. Graft survival, histopathology and level of serum IL-2, IFN-γ, IL-4, IL-10 were investigated. Results Low doses of FTY720 (1mg/kg) combined with ICAM-1 mAb achieved synergistic effect in the prolongation of cardiac graft survival, combination index(CI)=0.67. Conclusion Concomitant therapy of FTY720 and ICAM-1 mAb achieved a synergistic effect in the prolongation of heart allograft survival in rats.