Two cases of colon LST in transplanted liver patients

Long-life immunosuppressive therapy increases the risk of de novo tumors in liver transplant recipients by decreasing the immune surveillance against malignant cells and oncogenic viruses. However, no cases of colon precancerous lesions have been reported in these subjects. Patient n. 1, a 73 yrs old male treated with calcineurin and purine synthesis inhibitors, showed at a per-protocol colono-scopy a 3 cm laterally spreading tumor (LST). Patient n. 2, a 73 yrs old male treated with calcineurin inhibitors, showed at a screening colonoscopy an LST occupying one third of the lumen circumference. Both subjects were asymptomatic, had been transplanted 14 years before, and in both cases, lesions showed severe dysplasia. LSTs represent 17.2% of advanced colorectal neoplasia (CRC) and risk factors are multifactorial. Immunosuppression may play a role which is however not completely understood. Based on this report, surveillance colonoscopy in liver transplanted patients should be considered.

Differences in Peripheral Blood Lymphocytes between Brand-Name and Generic Tacrolimus Used in Stable Liver Transplant Recipients

OBJECTIVES

In this study, peripheral blood lymphocytes were compared between a brand-name and a generic tacrolimus group in stable liver transplant recipients.

SUBJECTS AND METHODS

Sixteen patients who underwent ABO-compatible living donor liver transplants between 2012 and 2013 and had stable graft function were included in this study. Ten patients received brand-name tacrolimus and 6 patients received generic tacrolimus. CD3, CD4, CD8, γδ, CD4+FoxP3+, and CD3-CD56+ T cells were analyzed in peripheral blood obtained preoperatively and 4, 8, 12, and 24 weeks after liver transplantation. Categorical variables were compared using a χ2 test or Fisher exact test, and continuous variables were compared using the Mann-Whitney U test.

RESULTS

Regarding the baseline and perioperative characteristics, there were no statistically significant differences between the 2 groups. Immunosuppression also was not different. Subtype analysis of T-cell populations carried out in parallel showed similar levels of CD3, CD4, CD8, and γδT cells with brand-name tacrolimus and generic tacrolimus in stable liver transplant recipients. However, the levels of CD4+Foxp3+ and CD3-CD56+ T cells were higher in the brand-name tacrolimus group than in the generic tacrolimus group 8 weeks after transplantation (p < 0.05).

CONCLUSIONS

The level of CD4+Foxp3+ T cells was higher in the brand-name tacrolimus group than in the generic tacrolimus group after transplantation. This finding showed that brand-name tacrolimus could have more potential immunosuppressive activity than generic tacrolimus regarding the contribution of CD4+Foxp3+ T cells to graft tolerance in liver transplant recipients.

Graft Expression of p38 and Tumor Necrosis Factor-α in Heart Transplantation in Rats

Objectives

To investigate the expression of p38 mitogen-activated protein kinase and its relationship with myocardial apoptosis and tumor necrosis factor-α during acute cardiac allograft rejection and to study the effects of tacrolimus on the expression of the kinase.

Methods

Rats were divided into 3 groups: isograft (Lewis heart to Lewis rat; control group), allograft (Brown Norway heart to Lewis rat), and tacrolimus-treated allograft (Brown Norway heart to tacrolimus-treated Lewis rat). Grafts were collected 1, 3, 5, and 7 days after transplantation for determination of histopathological features, apoptosis of cardiac cells (by terminal deoxynucleotidyl transferase–mediated dUTP-biotin nick labeling), number of cells positive for both p38 and CD8 (by laser scanning confocal imaging), and expression of the kinase (by Western immunoblotting) and tumor necrosis factor-α (by reverse-transcriptase polymerase chain reaction).

Results

Compared with isografts from the control group, grafts from the untreated allograft group had significantly more apoptotic cells, greater expression of tumor necrosis factor-α and p38 mitogen-activated protein kinase, and more CD8-p38 double-positive cells at 5 and 7 days ( P<.05). The increases were prevented by treatment with tacrolimus.

Conclusions

The findings that the number of apoptotic cells, the number of CD8-p38 double-positive cells, the expression of tumor necrosis factor-α and p38 mitogen-activated protein kinase all increased during the same period in the allografts in nonimmunosuppressed recipients suggests that intragraft expression of p38 would be associated with the rejection in acute cardiac allograft rejection. Tacrolimus may alleviate rejection partly by inhibiting p38 mitogen-activated protein kinase.

Evaluation of the Dade Behring Syva® EMIT 2000 tacrolimus assay on the Bayer Advia 1650

Background: The Dade Behring Syva® EMIT (enzyme multiplied immunoassay technique) method for the measurement of tacrolimus in whole blood was evaluated against the Abbott IMx® microparticle enzyme immunoassay (MEIA) method. EMIT measures tacrolimus colorimetrically, whereas MEIA measures the analyte using fluorimetry. Both methods incorporate a protein precipitation step prior to measurement.

Method: Whole blood specimens were treated by two types of precipitation technique followed by analysis for tacrolimus by either MEIA or EMIT on the Bayer Advia 1650. Linearity and precision were assessed and correlation analysis performed to evaluate the EMIT assay on the Bayer Advia 1650.

Results: The EMIT tacrolimus assay was linear over the concentration range 0.0-22.0 µg/L; the limit of detection was 1.2 µg/L. Correlation between the Syva EMIT and IMx tacrolimus assays was excellent ( r = 0.959) and no significant bias existed between the two methods (mean difference, δ = 0.221 µg/L). Calibration data for the EMIT assay was stable for a period of 24-48 h on the Advia between runs.

Conclusion: The Syva EMIT assay for the measurement of tacrolimus in whole blood is suited for daily routine use on the Bayer Advia 1650.

Tacrolimus for the prevention and treatment of rejection of solid organ transplants

Since its introduction to the antirejection armamentarium in 1994, tacrolimus has become the workhorse of transplant professionals for avoidance of solid organ transplant rejection. Not only does tacrolimus have potent immunosuppressive qualities that prevent rejection, but dosing is straight forward and it is generally well tolerated. However, in the long term, conditions such as calcineurin inhibitor nephrotoxicity can become a problem. A discussion of the compound, the pharmacokinetics, history, and current approved uses for tacrolimus is described. Indeed, tacrolimus is the most important drug for preventing transplant rejection. However, the increased appreciation for significant side effects, particularly in the long term, has led to building interest in new agents with different mechanisms of action and different metabolism.

Post-transplant food allergy in children is associated with liver and not with renal transplantation: a monocentric comparative study

Food allergy is increasingly reported after paediatric liver transplantation. The underlying physiopathological mechanism remains incompletely understood. Therefore, we aimed to determine the incidence, clinical presentation, possible risk factors, and prognosis of post-transplant food allergy in children currently followed after liver and renal transplantation. The study population consists of 49 liver and 21 renal transplant patients transplanted between the age of 22 months and 15 years. Data were collected retrospectively from medical records and via a doctor's questionnaire taken from the parents in a monocentric setting. Post-transplant food allergy has developed in 13 liver transplant patients and in none of the renal transplant recipients. Within the liver transplant group, median age at liver transplantation is significantly lower in the food-allergic (10 months) versus non-food-allergic group (3.3 years; p = 0.002). The use of tacrolimus as primary maintenance immunosuppression is associated with food allergy (p = 0.032) and mean donor age is significantly lower in the food-allergic group (p = 0.009). Compared to the renal transplant group, median age at transplantation is significantly lower in the liver patients (p < 0.001). No significant differences are found in primary immunosuppressive regimens between renal and liver transplant patients.

CONCLUSION

Post-transplant food allergy is an important clinical problem in children after liver transplantation which does not affect renal transplant patients despite similar immunosuppressive regimens. Within the group of liver transplant recipients, tacrolimus use, young age at time of transplant and younger donor age were associated with the development of food allergy.

LetterEvidence of Association between FKBP1B and Thyroid Autoimmune Disorders in a Large Tunisian Family

FKBP1B belongs to immunophilins superfamily and functions as a cytosolic receptor protein of FK506. The role of FKBP1B in the immunosuppressive pathway of FK506 is well established. Previously, we reported a strong evidence of linkage between D2S171 microsatellite marker (located in vicinity of FKBP1B gene) and susceptibility to autoimmune thyroid diseases (AITDs). In this study, we report linkage disequilibrium between the dimorphism (C/T) in the 3' untranslated region (3' UTR) of FKBP1B gene and susceptibility to AITDs. DNAs were extracted from a large Tunisian family affected with Graves' disease (GD) and Hashimoto's thyroiditis (HT) and analysed by PCR-RFLP using DraIII restriction enzyme. Our results showed an excess of transmission of the allele C from heterozygous parents to affected offspring (transmission disequilibrium test (TDT) = 4.76; p = 0.012). This suggests a linkage disequilibrium of 3' UTR (C/T) SNP with AITDs. Moreover, The FBAT analysis gives a significant association with the C allele under the recessive model (chi2 = 5.50; p = 0.018). These results support the involvement of FKBP1B gene in the genetic susceptibility to the AITDs development in the studied family.

Allergic contact dermatitis from pimecrolimus in a patient with tacrolimus allergy

A 15-year-old male with previously documented allergic contact dermatitis from tacrolimus was allergic to pimecrolimus. This was demonstrated by double-blinded, right-versus-left provocative use testing with pimecrolimus cream 1% versus inactive vehicle applied twice daily to normal skin. The active cream but not its vehicle caused preauricular dermatitis starting after 1 week and caused isolated papules on the extensor wrist starting after 2 weeks. Patch testing on the patient's back was weakly positive (1+) with pimecrolimus cream 1% and negative with the vehicle. Higher concentrations of pimecrolimus were not available for testing. Patch tests on 30 control patients with pimecrolimus cream 1% were negative.

Immunosuppression on the Horizon

Many novel immunosuppressive agents are under active clinical investigation. In addition, creative approaches are being developed for the use of established immunosuppressive agents, with the goal of minimizing immunosuppression as early as possible posttransplantation. The hope is that these approaches will minimize the toxicity of these agents without sacrificing efficacy. Evidence suggests that the nephrotoxicity of calcineurin inhibitors can be reduced using these approaches. The introduction of newer immunosuppressive agents, including the proliferation signal inhibitors, raises the possibility that some of the long-term scourges of cardiac transplantation, including cardiac allograft vasculopathy and malignancy, can be ameliorated. Finally, costimulatory pathway inhibitors and other new immunosuppressive agents offer hope that all these goals can be accomplished with very low long-term maintenance immunosuppression.

Targeted ITP strategies: do they elucidate the biology of ITP and related disorders?

An elusive goal in hematology is a detailed understanding of autoimmune blood disorders including idiopathic (immune) thrombocytopenic purpura (ITP), autoimmune hemolytic anemia (AIHA), and Evans Syndrome. While it is clear that these disorders have an autoimmune pathophysiology, the exact mechanisms are not clear. Agents that target the immune system specifically, such as rituximab and tacrolimus, are currently being used clinically with favorable results. Targeted therapy may be useful not only in treating these difficult diseases, but also may provide clues to the underlying disease pathophysiology. Carefully designed studies using targeted therapy may provide biologic predictors of disease severity, as well as predictors of response to therapy.

Tacrolimus immunosuppression in high-risk corneal grafts

BACKGROUND

Unlike the immune privilege enjoyed by low-risk corneal grafts, high-risk corneal grafts experience rejection rates comparable to liver and kidney transplants. Systemic immunosuppression reduces the risk of rejection in high-risk corneal grafts.

METHODS

Systemic tacrolimus, a specific T cell inhibitor, was used at a mean daily dose of 2.5 mg to immunosuppress 43 patients undergoing high-risk corneal transplantation. Immunosuppression was continued for a period of 18-24 months after the high-risk corneal graft.

RESULTS

During a mean follow-up period of 33.7 months, clarity of the graft was maintained in 65% of patients. Eight patients experienced rejection episodes while on tacrolimus, and this led to graft failure in five patients.

CONCLUSION

Tacrolimus is relatively safe and effective in reducing rejection and prolonging graft survival in patients with high-risk keratoplasty compared with other series where similar immunosuppression was not used.

Ten-year protocol biopsy findings of renal allografts in the calcineurin inhibitor era

Ten-year protocol biopsies were performed in 16 patients treated with calcineurin inhibitor (CNI) continuously. All kidney grafts were functioning well at the time of biopsy with the mean serum creatinine level of 1.6 +/- 0.8 mg/dL. The specimen of biopsy showed various degrees of tissue injury. According to the Banff grading, allograft glomerulopathy (cg) was observed in one case. Interstitial fibrosis (ci) and tubular atrophy (ct) were observed more frequently in 13 (81%) and 15 (93%) cases, respectively. Fibrous intimal thickening (cv) was seen in one (7%) case. Arteriolar hyaline thickening (ah) was seen in 14 (87%) cases. These findings were associated with chronic rejection in one case, recurrence of original disease in four (25%) cases, toxicity of CNI in 14 (87%) cases. Longer follow-up studies are needed to confirm whether CNI should be continued or not in the long-term period following kidney transplantation for better graft survival.

Significant improvement in the outcome of HCV-infected transplant recipients by avoiding rapid steroid tapering and potent induction immunosuppression

BACKGROUNDS/AIMS

Recurrent HCV-cirrhosis occurs in a substantial proportion of transplant recipients, with higher rates reported in patients who had recently received a transplant. Over-immunosuppression has been implicated in this more unfavorable outcome. To determine whether the implementation of specific measures aimed at reducing or avoiding negative predictive variables is associated with an improvement in the outcome of recurrent hepatitis C.

METHODS

Comparative study between a cohort of patients who had recently received a transplant (2001-2004) and a historical group of HCV-infected patients transplanted before the implementation of two simple measures (1999-2000): (i) use of dual initial immunosuppression (steroids + cyclosporine neoral or tacrolimus); (ii) slow steroid tapering (>6 months). Yearly biopsies were performed in these recipients, and only those with at least one protocol biopsy and those with cholestatic hepatitis (regardless of follow-up) were included in the study. End-point: rate of HCV-related severe disease (defined as bridging fibrosis, cirrhosis or fibrosing cholestatic hepatitis) within the first year post-transplantation.

RESULTS

Severe disease was significantly lower in this cohort compared to the historical group (26/90, 29% vs 25/52, 48%; p=0.02). While other factors remained unchanged between the two cohorts, the proportion of patients on triple-quadruple regimes and the number of boluses of methyl-prednisolone were lower and the duration of prednisone therapy longer in more patients who had recently received a transplant.

CONCLUSIONS

Improving the outcome of recurrent hepatitis C may be achieved by reducing overall immunosuppression and avoiding abrupt variations in immunosuppression.

Acquired Pelger-Huët anomaly in association with concomitant tacrolimus and mycophenolate mofetil in a liver transplant patient: a case report and review of the literature

Pelger-Huët anomaly is a congenital or acquired abnormality of neutrophil nuclear segmentation. The acquired form may be a result of a clonal myeloid malignancy, such as myelodysplastic syndrome, or may be a secondary nonclonal change related to a variety of underlying causes, including infections and medications. We report a case of a 56-year-old man who developed acquired Pelger-Huët anomaly following liver transplantation while on the immunosuppressive agents tacrolimus and mycophenolate mofetil. These medications have been reported in association with this abnormality, but usually as a single agent or in combination with other drugs. In our case, the Pelger-Huët anomaly may be the result of the combination of these 2 drugs or mycophenolate alone with subsequent desensitization because resolution of the abnormality occurred after a reduction in mycophenolate mofetil dose, and the abnormality did not recur when mycophenolate mofetil was increased to a dose previously associated with Pelger-Huët anomaly during the time that tacrolimus was discontinued.

The portal immunosuppressive storm: relevance to islet transplantation?

Outcomes in clinical islet transplantation improved substantially with the introduction of combined sirolimus and tacrolimus immunosuppression. However, multiple islet preparations are often required to achieve insulin independence, suggesting that islet engraftment may not be optimal when these agents are absorbed via the portal vein. The current study was designed to assess the differential concentrations of immunosuppressive drugs within the portal and systemic circulations of a large animal model, to assess the local concentrations of drugs to which islets are exposed early after implantation. Chronic catheters were placed in the portal vein and carotid artery of 6 mongrel dogs, and immunosuppressants were administered orally. Blood samples were drawn simultaneously from portal and systemic catheters, and drug concentrations were analyzed. Peak immunosuppressant levels as well as area under the curve were dramatically elevated in portal blood relative to systemic levels for all drugs tested. This "portal storm" of immunosuppression may be relevant to intrahepatic islet transplantation.

Hematocrit Influences Immunoassay Performance for the Measurement of Tacrolimus in Whole Blood

The comparison between the MEIA II and the EMIT assays for tacrolimus measurement and the interference by the hematocrit were evaluated in 93 samples from routine therapeutic monitoring at tacrolimus concentrations less than 9 microg/L (group A). Additionally, the incidence of false-positive results were determined in samples (n=46) from patients who were not receiving the drug (group B). In group A, no statistical differences were observed between the mean+/-SD values obtained by MEIA II (5.14+/-2.28 microg/L) and EMIT (4.61+/-1.79 microg/L). The correlation coefficient and the regression equation (95% CI) between both assays, were 0.761 and EMIT=1.088 (0.90, 1.35) MEIA II -0.38 (-1.65, -0.46), respectively. When the samples were stratified according to the hematocrit, the median differences between the methods (MEIA II minus EMIT) were as follows: hematocrit<or=25%, 0.45 microg/L; hematocrit 25%-35%, 0.30 microg/L; and hematocrit>35%, 0.25 microg/L (P=0.02). In group B, false-positive results (above the detection limit) were observed in 63.04% of samples analyzed by MEIA II and in 2.17% of samples analyzed by EMIT. The median differences in apparent tacrolimus results were significantly higher in the samples with the lowest hematocrit: 2.2 microg/L, 1.4 microg/L, and 0.0 microg/L in samples with hematocrit<or=25%, 25%-35%, and >35%, respectively. In conclusion, the differences in the tacrolimus results obtained by MEIA and EMIT assays were higher in samples from patients with hematocrit less than 25%, and the MEIA assay demonstrated a high incidence of false-positive results.

Review of the potential photo-cocarcinogenicity of topical calcineurin inhibitors. Position statement of the European Dermatology Forum

Topical Calcineurin Inhibitors (TCIs) used for the treatment of atopic eczema modify the immune regulatory function of the skin and may have the potential to enhance immunosuppressive ultraviolet (UV) effects. Current recommendations on UV protection in eczema patients treated with PCIs are inconsistent and have given rise to uncertainty and anxiety in patients. Therefore, the European Dermatology Forum (EDF) developed a position statement which reviews critically the available data with regard to the problem, especially analysing and commenting the limitations of rodent models for the human situation. There is no conclusive evidence from rodent trials to indicate that long-term application of TCIs is photococarcinogenic. There is a need for further studies to investigate the validity of mouse models as well as long-term cohort studies in patients using TCIs. Available data suggest that long-term application of TCIs is safe, that there is no evidence of increased skin cancer risk and that it is ethical to treat patients with TCIs when indicated.

Multiglycosidorum tripterygii versus Tacrolimus for rat tracheal allografts

OBJECTIVE

Several other immunosuppressive agents still need to be found for rejection as alternatives to Tacrolimus in lung transplantation. We tried to elucidate the treatment effect of Multiglycosidorum tripterygii on tracheal allografts in comparison to that of Tacrolimus.

METHODS

Treatment effect of agents on tracheal allografts, undergoing incomplete immunosuppression for 12 weeks after transplantation, was investigated using a heterotopic rat tracheal transplantation model. Treatments with Tacrolimus (1.0 or 1.5mg/kg per day), Multiglycosidorum tripterygii (150 or 225mg/kg per day) and a combination of Tacrolimus (1.0mg/kg per day) and Multiglycosidorum tripterygii (150mg/kg per day) were applied as a therapy for allografts. Four weeks after administering this therapy, the effect of each treatment was investigated by the morphologic assessment of transplants.

RESULTS

Treatment group with high doses of Multiglycosidorum tripterygii demonstrated a significantly better graft patency and lower cartilage dislocation than that without any treatment and tended to show better morphological findings than the other treatment groups, in addition to being safe. Some of allografts with high doses of Tacrolimus or Multiglycosidorum tripterygii therapy had a viable epithelium and viable tracheal glands in part, whereas the allografts with other treatments showed almost a completely denuded epithelium. High doses of Multiglycosidorum tripterygii therapy demonstrated less infiltration of mononuclear cells into the allografts, whereas other therapies showed a higher infiltration of such cells.

CONCLUSIONS

We conclude that high doses of Multiglycosidorum tripterygii may be a useful alternative to Tacrolimus as an immunosuppressant for rat tracheal allografts.

Inflammatory cell numbers and cytokine expression in atopic dermatitis after topical pimecrolimus treatment

BACKGROUND

In several clinical trials the topical application of pimecrolimus was shown to be effective in the treatment of atopic dermatitis (AD). By targeting calcineurin-dependent signaling pathways, pimecrolimus controls cytokine gene expression. The purpose of this study was to investigate the effect of pimecrolimus on the inflammatory infiltrate and cytokine expression pattern in AD upon topical therapy.

METHODS

From 10 patients with acute AD, skin biopsies as well as immunophenotype and cytokine production of peripheral blood mononuclear cells (PBMC) were examined before and 3 weeks after therapy.

RESULTS

The clinical improvement was associated with a marked regression of histopathological features. In particular, the density of the inflammatory infiltrate mostly containing lymphocytes and eosinophils declined. By double immunofluorescent staining, a reduced expression of the T helper (Th) 2 cytokines interleukin (IL)-5, IL-10, and IL-13 in both CD4+ and CD8+ T cells was demonstrated after therapy. Pimecrolimus therapy was also associated with a reduced expression of the Th1 cytokine interferon (IFN)-gamma. Interestingly, the numbers of epidermal CD1a+ dendritic cells increased following treatment. In the peripheral blood, a decrease of lymphocytes and eosinophils was noticed, but the distribution of lymphocyte subpopulations and their capacity of cytokine production did not change.

CONCLUSIONS

Topical pimecrolimus exhibits anti-inflammatory effects in AD by reducing the inflammatory cell infiltrate and cytokine expression in the dermis.

Donor cell engraftment in recipient lymphoid tissues after rat limb allograft

BACKGROUND

The movement of cells from a transplanted tissue into the host organs, the so-called systemic chimerism, is a phenomenon known to occur and be associated with the development of immunologic tolerance in allotransplantation cases. The purpose of this study was to identify donor cell engraftment in recipient lymphoid tissues after performing rat hind limb allograft.

MATERIALS AND METHODS

Fifty-five whole-limb allotransplantations were performed in sex-mismatched pairs of rats. Syngeneic male Lewis and allogeneic Dark Agouti donors were transplanted to female Lewis recipients. FK506 was used for immunosuppression. Donor male cells could be identified in the recipient female tissues by semiquantitative polymerase chain reaction analysis for a Y chromosome-specific DNA sequence. Chimerism was assessed at 1, 24, and 48 weeks after transplantation.

RESULTS

There was no rejection episode in any of the limb grafts. Although levels of chimerism were highly variable in each lymphoid tissue, a gradual increase was noticed in all during the course of time. At 1 week after the transplant period, only intrasplenic chimerism was at high level (1%) in three groups. At 48 weeks after the transplant, all recipients with allografts showed very high level (10%) of chimerism in the bone marrow. Two, two, and two of six recipients showed very high levels in the spleen, lymph node, and liver, respectively, at 48 weeks. Intrathymic chimerism was higher at 24 weeks after transplant rather than at 48 weeks.

CONCLUSION

We demonstrated donor cell engraftment into recipient lymphoid tissues after successful whole limb transplantation. We conclude that limb allograft can work as a vascularized carrier for the bone marrow transplantation, provide a continuous source of donor cells and contribute to chimerism in the recipient.

A prospective 3-yr evaluation of tacrolimus-based immunosuppressive therapy in immunological high risk renal allograft recipients

BACKGROUND

There have been no published data on use of the the newer immunosuppressants tacrolimus and mycophenolate mofetil (MMF) in high immunological risk renal transplantation. We therefore undertook a prospective study to systematically assess outcomes using these agents as part of an aggressive immunosuppressive regimen.

METHODS

Fifty-nine high-risk renal allograft recipients were enrolled at 10 Canadian sites and given a regimen of: a biological induction agent, tacrolimus, MMF, and corticosteroids. Patients included 10 (17%) who had lost a previous graft to rejection <1 yr, 31 (53%) with a current panel reactive antibody (PRA) >30%, 47 (80%) with a historic PRA >50%, four (7%) who had a positive historical T-cell crossmatch with the current donor, and six (10%) with a current positive B-cell crossmatch. The mean peak PRA was 76 +/- 33%.

RESULTS

The estimated 3-yr Kaplan-Meier patient and graft survival estimates were 89% and 75%, respectively. There were nine graft losses other than deaths with a functioning graft, of which six were preceded by delayed graft function (p = 0.01, chi2). Sixteen (27%) recipients experienced at least one episode of biopsy-confirmed acute rejection. Infections included cytomegalovirus in 16 patients, eight of whom had tissue-invasive disease. Only one malignancy occurred.

CONCLUSIONS

The immunosuppressive strategy investigated is effective and displays a satisfactory safety profile in high immunological risk renal allograft recipients.

FK1706, a novel non-immunosuppressive immunophilin: neurotrophic activity and mechanism of action

Immunophilin ligands are neuroregenerative agents, characterized by binding to FK506 binding proteins (FKBPs), which stimulate recovery of neurons in a variety of injury paradigms. Here we report the discovery of a novel, non-immunosuppressive immunophilin ligand, FK1706. FK1706, a derivative of FK506, showed similarly high affinity for two FKBP subtypes, FKBP-12 and FKBP-52, but inhibited T-cell proliferation and interleukin-2 cytokine production with much lower potency and efficacy than FK506. FK1706 (0.1 to 10 nM) significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in SH-SY5Y cells, as did FK506. This neurite potentiation could be blocked by an anti-FKBP-52 antibody, as well as by specific pharmacological inhibitors of phospholipase C (PLC), phosphatidylinositol 3-kinase (PI3K), and the Ras/Raf/Mitogen-Activated Protein Kinase (MAPK) signaling pathway. FK1706 also potentiated NGF-induced MAPK activation, with a similar dose-dependency to that necessary for potentiating neurite outgrowth. Taken together, these data suggest that FK1706 is a non-immunosuppressive immunophilin ligand with significant neurotrophic effects, putatively mediated via FKBP-52 and the Ras/Raf/MAPK signaling pathway, and therefore that FK1706 may have therapeutic potential in a variety of neurological disorders.

Novel rescue therapy for C4d-positive acute humoral renal allograft rejection

OBJECTIVE

To investigate the efficacy of immunoadsorption (IA) in combination with tacrolimus (TAC) and mycophenolate mofetil (MMF) rescue therapy for C4d-positive acute humoral rejection (AHR) of renal transplants.

METHODOLOGY

Six of 185 cadaveric renal allograft recipients transplanted at our institute developed AHR over a mean period of 4.8 +/- 0.8 d after operation. The ages ranged from 35 to 51 yr (mean 42.6 +/- 5.6 yr). C4d deposits in peritubular capillaries (PTC) and accumulation of granulocytes in PTC were observed. IA with staphylococcal protein A and TAC-MMF combination therapy were given.

RESULTS

After subjected to IA for 6.3 +/- 1.03 sessions combined with TAC (0.14-0.16 mg/kg/d) and MMF (1.5 g/d) therapy, renal function recovered in all the patients. The mean duration of treatment when serum creatinine decreased was 14 +/- 2.9 d. The pre-IA panel reactive antibody reactivity was as high as 50.2 +/- 6.1%, and was significantly reduced to 8.3 +/- 2.9% after IA. Repeated allograft kidney biopsy in four of six patients revealed a favorable remission of AHR. With a mean follow-up of 18.8 +/- 5.46 months, patient and allograft survival are 100%, renal function remained stable with a mean serum creatinine of 1.2 +/- 0.22 mg/dL.

CONCLUSION

The optimal treatment for alloantibody-mediated AHR remains undefined. Our findings suggest that a therapeutic approach combining IA and TAC-MMF rescue has excellence to improve the outcome of AHR.

Reduced dermal infiltration of cytokine-expressing inflammatory cells in atopic dermatitis after short-term topical tacrolimus treatment

BACKGROUND

In several clinical studies, topical calcineurin inhibitors have been shown to be effective in the treatment of atopic dermatitis (AD). They target signaling pathways that control gene expression, particularly the expression of cytokines.

OBJECTIVE

We examined the cellular infiltrate in skin lesions of 10 patients with AD and characterized the cytokine pattern expressed by the infiltrating cells before and after short-term topical therapy with tacrolimus 1% ointment.

METHODS

Skin biopsies were examined for histologic alterations (hematoxylin and eosin staining), composition of the cellular inflammatory infiltrate (immunofluorescence), and cytokine expression (ribonuclease protection assay, ELISA, immunofluorescence) before as well as 1 and 3 weeks after initiation of tacrolimus therapy. For comparison, biopsies from nonlesional AD and normal skin were analyzed. Systemic immunologic effects were assessed by analyzing peripheral blood leukocytes (immunofluorescence) as well as in vitro stimulated pan-T-cell cytokine production (ELISA).

RESULTS

All patients showed a significant improvement of their skin lesions associated with a marked regression of spongiosis, acanthosis, and density of the cellular infiltrate in the dermis. The last was a result of reduced infiltration of T cells, B cells, and eosinophils. In contrast, the numbers of mast cells did not change. Moreover, the expression of the T H 2 cytokines IL-5, IL-10, and IL-13 in CD4 + T cells was reduced after therapy. Interestingly, tacrolimus therapy was also associated with a reduction of CD8 + T cells expressing the T H 1 cytokine IFN-gamma. Furthermore, the numbers of epidermal CD1a + dendritic cells increased after treatment. In the peripheral blood, a decrease of granulocytes (eosinophils and neutrophils) but no changes in the distribution of lymphocyte subpopulations were noticed.

CONCLUSION

Topical tacrolimus treatment has anti-inflammatory effects on AD skin as indicated by reduced infiltration of cytokine expressing inflammatory cells. No evidence for drug-induced systemic immunosuppression was obtained.

Anemia in children after transplantation: etiology and the effect of immunosuppressive therapy on erythropoiesis

Anemia in children after renal transplantation is more common than previously appreciated. Multiple factors appear to play roles in the development of post-transplant anemia, the most common of which is absolute and/or functional iron deficiency anemia. Most experts recommend that iron limited anemias in transplant patients should be diagnosed using the same criteria as for chronic renal failure patients. Serum erythropoietin (EPO) levels are expected to normalize after a successful renal transplantation with a normal kidney function, yet both EPO deficiency and resistance have been reported. While no large controlled trials comparing the effect of different immunosuppressive agents on erythropoiesis after transplantation have been performed, generalized bone marrow suppression attributable to azathioprine (AZA), mycophenolate mofetil (MMF), tacrolimus, antithymocyte preparations has been reported. Pure red cell aplasia (PRCA) occurs rarely after transplantation and is characterized by the selective suppression of erythroid cells in the bone marrow. PRCA has been reported with the use of AZA, MMF, tacrolimus, angiotensin converting enzyme inhibitors (ACEI), but not with cyclosporine (CSA) use. Post-transplant hemolytic uremic syndrome has been reported with orthoclone anti T-cell antibody (OKT3), CSA and tacrolimus therapy. Viral infections including cytomegalovirus, Epstein-Barr virus and human parvovirus B19 have been reported to cause generalized marrow suppression. Management of severe anemia associated with immunosuppressive drugs generally requires lowering the dose, drug substitution or, when possible, discontinuation of the drug. Because this topic has been incompletely studied, our recommendation as to the best immunosuppressive protocol after renal transplantation remains largely dependent on the clinical response of the individual patient.

[Drug of month. Topical tacrolimus (Protopic)]

Tacrolimus is a potent inhibitor of immune mechanisms. It belongs to the macrolactam group. It inhibits the release of both Th1 and Th2 cytokines. It proves to be efficacious after topical application in the treatment of atopic dermatitis. In this indication, tacrolimus challenges topical corticosteroids. Irritation risks are present. The local immuno-depression can boost disseminated infections including herpes. The risk to promote photocarcinogenesis on the long term, and that bound to chronic resorption remain theoretical concerns that have not been assessed so far.

Enhancement of immune tolerance via induction of NK1.1 positive liver-associated-lymphocytes under immunosuppressive conditions

BACKGROUND/AIMS

The liver was previously shown to play a critical role in oral tolerance induction. A subset of liver-associated-lymphocytes expressing NK1.1 marker (NK1.1+ LAL) have killing activities and it has been suggested that they play a role in immune modulation. FK506 is a powerful immunosuppressive agent affecting T-cell differentiation and function. The exact pathway involved in peripheral tolerance induction using this drug remains unknown. The aim of the present study was to determine the interaction between FK506 and NK1.1+ LAL in induction of peripheral immune tolerance in the experimental colitis model.

METHODS

Colitis was induced in C57 mice by intracolonic instillation of trinitrobenzenesulfonic acid (TNBS). Mice received five oral doses of colonic proteins extracted from TNBS-colitis colonic wall with and without FK506 treatment. The effect of FK506 treatment on NK1.1+ LAL was tested by cell-sorting and cytotoxicity assay. Colitis was assessed by standard clinical, macroscopic and histologic scores.

RESULTS

Both FK506 treatment and oral tolerance induced a significant increase in NK1.1+ LAL number and cytotoxicity function. FK506 treatment enhanced the effect of oral tolerance on amelioration of disease activity. Orally tolerized mice treated with FK506 had no mortality nor increase in body weight, and manifested significant improvement in disease macroscopic and microscopic scores.

CONCLUSIONS

This study shows for the first time that immune tolerance induced by both oral administration of an antigen and by FK506 treatment may be mediated via enhancement of NK1.1+ LAL. This subset of lymphocytes may play an immunoregulatory role in immune tolerance induction.

Immune response to adenovirus-delivered antigens upregulates utrophin and results in mitigation of muscle pathology in mdx mice

The upregulation of endogenous utrophin in skeletal muscle may lead to a new approach to the treatment of Duchenne muscular dystrophy (DMD). We found that injection of an E1, E3-deleted adenovirus vector expressing beta-galactosidase (beta-Gal) or green fluorescent protein (GFP) into the skeletal muscle of neonatal dystrophin-deficient mdx mice alleviated dystrophic pathology. In the adenovirus-infected muscles, an evaluation of sarcolemma stability showed low permeability and immunohistochemistry revealed utrophin upregulation at the extrasynaptic sarcolemma of mature muscle fibers. This utrophin upregulation was concomitant with endomysial cellular infiltration from a host immune reaction. There was no evidence of active muscle regeneration. In normal C57BL/10 mice, utrophin was also upregulated in adenovirus-injected skeletal muscles, where upregulated utrophin often coexisted with dystrophin. FK506 and anti-CD4 antibody administration decreased utrophin expression in adenovirus-injected mdx muscles and prevented the dystrophic phenotype from being mitigated, suggesting that an immune reaction is involved in utrophin upregulation. This is the first report demonstrating the improvement of the dystrophic phenotype as a result of the acquired overexpression of endogenous utrophin. Our findings provide an important clue to understanding the mechanism of utrophin expression and the development of an effective treatment for DMD.

[Role of calcineurin-dependent drugs on the immunosuppressive effect induced by the anti-LFA-1 antibody in a fetal intestinal transplantation model in mice]

STUDY AIM

We have previously demonstrated that anti-LFA-1 monoclonal antibody (mAb) can efficiently protect against rejection of small bowel allograft in a mouse model. The aim of the present work was to determine, in the same model, the optimum conditions for utilisation of anti-LFA-1 mAb and the effects of calcineurin-dependent drugs on the immunosuppression induced by anti-LFA-1 mAb treatment.

MATERIALS AND METHODS

Foetal small intestines of C57Bl/6 (H-2b) mice were transplanted into adult C3H/He (H-2k) mice. Recipients were treated with anti-LFA-1 mAb alone (with or without day-1 injection), or combined to cyclosporin (20 mg.kg-1.j-1 for 14 days), or to tacrolimus (1 mg.kg-1.j-1 from day 0 to day 7). Biopsies were performed after engraftment from day 5 to day 30.

RESULTS

Administration of anti-LFA-1 mAb alone is sufficient to induce significant prolongation of intestinal allograft survival, provided that the treatment starts one day before engraftment. This tolerogenic effect is reversed by the transitory administration of tacrolimus (p = 0.008).

CONCLUSION

Treatment with anti-LFA-1 mAb has to be started before the allogeneic response has begun. Calcineurin-dependent drugs can modulate the tolerogenic effect induced by anti-LFA-1. A transgenic mice model should give precise details about underlying mechanisms of these interactions, before a possible utilisation of anti-LFA-1 mAb in intestinal transplantation in humans.

Autoantibodies to FK506 binding protein 12 (FKBP12) in autoimmune diseases

Plasma from 126 patients with various autoimmune diseases and 118 healthy subjects were examined to determine the presence of autoantibodies to FKBP12, one of immunophilins. The frequency of IgG and/or IgM anti-FKBP12 autoantibodies detected by ELISA was as follows; SLE (15/39), SSc (11/27), CREST (4/7), RA (2/8), MCTD (0/5), Graves' disease (4/12), IDDM (2/6), PM/DM (0/3), MG (1/4), AIH (2/6), PBC (4/9), and healthy subjects (5/118). The specificity of the autoantibodies was demonstrated by absorption of the plasma samples with r-FKBP12 and other recombinant proteins. In immunoblotting, IgM anti-FKBP12 autoantibodies reacted with two bands of 12 and 24 kD, the latter representing the dimer. Anti-FKBP12 autoantibodies in some patients reacted more strongly with the dimer than the monomer, suggesting that FKBP12 may also exist as the dimer in vivo. The majority of anti-FKBP12 autoantibodies bound to two synthetic peptides corresponding to amino acid residues of FKBP12, Pro16 approximate to Tyr26 and Thr27 approximate to Phe46. These epitopes are phylogenetically well conserved and responsible for the binding to calcineurin and FK506. The autoantibodies inhibited pentamerization of FKBP12 with FK506, calcineurin, calmodulin, and Ca2+ in vitro. These data define the frequent occurrence of a novel set of autoantibodies to a cytosolic protein involved in the regulation of the immune response.

Long-term outcomes in pediatric liver recipients: comparison between cyclosporin A and tacrolimus

In recent years, tacrolimus (FK506, TAC) has been increasingly utilized in liver transplantation. However, long-term risks and benefits as compared with conventional cyclosporin A (CsA) have not been fully elucidated. This retrospective study examined the potential outcome differences between TAC- and CsA-based immunosuppressive therapy in pediatric liver transplant recipients. From March 1988 to December 1996, 218 children (aged 0.1-17 yr) underwent 238 orthotopic liver transplantations; 58.7% (128/218) were under 2 yr of age at time of transplant. Initially, the maintenance immunosuppressive regimen consisted of CsA and prednisone, with antilymphocytic preparations (MALG, ATGAM, and OKT3) as induction therapy. Subsequently, TAC was used first as rescue therapy for steroid refractory rejection in CsA patients and then as maintenance immunosuppression. Fifty-seven out of the 147 CsA patients were converted to TAC for various reasons while 71 patients were placed on TAC as primary maintenance immunosuppression. 62.6 per cent (92/147) of liver recipients on CsA experienced at least one biopsy-proven acute rejection episode as compared to 50.7% (36/71) for TAC patients (p = 0.09); likewise, 34% (50/147) of CsA patients had more than one episode of rejection vs. 18.3% (13/71) for patients on TAC (p < 0.02). Rejection was the reason for conversion from CsA to TAC in 29 of 57 patients. Conversely, 19.0% (28/147) of CsA patients had to be switched to TAC for reasons not related to rejection (i.e. side-effects). The overall incidence of histologically proven chronic rejection was 7.8% (17/218). 10.9 per cent (16/147) of the children who were on CsA initially developed chronic rejection, which was significantly higher compared with one of 71 TAC recipients (p < 0.02). Of these 16 CsA patients with chronic rejection, 50.0% (8/16) underwent retransplantation for graft failure (mean interval from time of diagnosis of chronic rejection to re-transplant, 4.0 months; range 1-8 months), whereas the TAC patient has remained clinically stable with normal liver function tests after 23 months of follow-up. One year after liver transplantation, 72.8% (107/147) of CsA patients were still on steroids (mean dosage 0.20 mg/kg/d), as compared to 42.3% (30/71) of the TAC patients (mean dosage 0.14 mg/kg/d). The incidence of post-transplant lymphoproliferative disorder (PTLD) in Epstein-Barr virus (EBV)-infected patients was 2.2% (2/90), 7.0% (5/71) and 12.3% (7/57) for CsA, primary and TAC-converted groups, respectively. The overall incidence of PTLD was 6.9% (15/218). In summary, pediatric liver transplant recipients treated with TAC as primary maintenance immunosuppressive medication experienced significantly fewer episodes of rejection; especially chronic rejection, which lead to graft loss. However, the trade-off is a potential increased incidence of EBV-related PTLD in these patients.

Tacrolimus in pediatric renal transplantation: a review

Tacrolimus is a T cell-specific immunosuppressive agent that has been used in a relatively small number of pediatric kidney transplant recipients. It has been used as a primary immunosuppressive agent, with patient survival rates of over 95%, and graft survival rates of over 90%. In the largest series reported, some two-thirds of the successfully transplanted recipients have been taken off steroids, with substantial catch-up growth, and over 80% have been taken off antihypertensive medications. Important complications have included EBV-related post-transplant lymphoproliferative disorder and post-transplant diabetes mellitus, both reversible. Tacrolimus has also been used to rescue patients with refractory acute rejection, with a success rate of 70%-75%. This review summarizes the current world experience with tacrolimus in pediatric renal transplantation, and describes the details of tacrolimus dosing and the treatment of tacrolimus-related complications. On balance, tacrolimus is an effective immunosuppressive agent and offers important advantages in the management of pediatric renal transplant recipients.

Tacrolimus metabolite cross-reactivity in different tacrolimus assays

OBJECTIVES

Tacrolimus (FK506) is an immunosuppressive drug with great clinical promise. There is a controversy regarding the role of tacrolimus metabolites in immunosuppression and toxicity, and immunoassays and immunophilin binding assays have not been adequately tested for metabolite cross-reactivity. Methods are limited to HPLC and HPLC-MS for quantifying the parent drug. Mixed lymphocyte culture assay (MLC) is the preferred functional bioassay for the measurement of parent drug and active metabolites but it is not practical for routine laboratory use. Due to differences in assay methods and reagent specificity, the concentration of tacrolimus in a given specimen may vary among different assay kit manufacturers. The objective of this study was to evaluate the degree of cross-reactivity or interference of the three first-generation tacrolimus metabolites [13-O-demethyl (M-I), 31-O-demethyl (M-II) and 15-O-demethyl (M-III)] among two different tacrolimus immunoassays (Immunoassay: PRO-Trac II FK506, Abbott IMx tacrolimus-II); and the radioreceptor assays (RRA) using minor immunophilins (14, 37, and 52 kDa immunophilins) and tacrolimus binding protein (FKBP12).

METHODS

First-generation tacrolimus metabolites (M-I, M-II, and M-III) spiked in drug-free whole blood were assayed with RRA using three minor immunophilins (14, 37, and 52 kDa) and two commercial immunoassay procedures (Incstar PRO-Trac II tacrolimus, Abbott IMx tacrolimus II). The results were compared to previously published FKBP-12 RRA data and their immunosuppressive potency.

RESULTS AND CONCLUSION

The first generation tacrolimus metabolites (M-I, M-II, and M-III) were tested using concentrations of 10 and 20 ng/mL. The significance of the metabolite interference (% of the total interference) was calculated based on the relative concentration of each metabolite present at steady-state trough concentrations in renal transplant recipients (22). Metabolite I, which has no functional immunosuppressive activity showed minimal interference compared to M-II and M-III in all assays except the 14 kDa RRA. The Incstar PRO-Trac II tacrolimus assay showed the least M-I interference. Metabolite-II, which has a pharmacologic potency similar to the parent drug, showed a significant interference in the immunoassays and significant interference in radioreceptor assays. Metabolite III, which is pharmacologically inactive, produces 3-10% interference in the different assays if its presence in the blood is 6% of the parent drug. The total interference from these three metabolites was greater in the immunoassays than in the receptor assays. Receptor assays for tacrolimus provide results closer to the target value than do immunoassays.

Comparison of different assays for the quantitation of FK 506 levels in blood or plasma

In a prospective study, we evaluated the analytical performance of different assays for the quantitation of FK 506 in blood and plasma. The new whole blood IMX assay was compared with four modifications (liquid/liquid or solid/liquid extraction of blood or plasma respectively) of the standard enzyme-linked immunosorbent assay (ELISA). Both assays utilize the same monoclonal antibody for detection of FK 506. Using isolated FK 506 metabolites generated in vitro, this antibody was shown to recognize not only the unmodified parent drug but also FK 506 metabolites. In stable liver-grafted patients, sensitivity of both modifications of the whole blood ELISA was adequate. In contrast, in some stable patients, plasma ELISA was not able to detect FK 506; this was observed mainly after liquid/liquid extraction of FK 506. Sensitivity of the IMX assay was also low; in six of 10 stable liver-grafted patients, IMX levels were below the limit of detection. In all assays, FK 506 levels were found to be elevated during episodes of liver dysfunction; a possible explanation for this effect would be that of accumulation of cross-reacting FK 506 metabolites. As FK 506 metabolites are known to be less immunosuppressive than the parent drug, liver function should always be taken into account if IMX or ELISA levels are used for drug monitoring.

Cyclosporin A and FK506: molecular mechanisms of immunosuppression and probes for transplantation biology

The microbial products cyclosporin A (CsA), FK506 and rapamycin are potent immunosuppressive agents. The introduction of CsA in the early 1970's significantly improved the outcome of organ and bone marrow allograft transplantation and advanced therapeutic options in autoimmune diseases. FK506 appears to have a higher therapeutic index than CsA, and has been used with encouraging results in clinical transplantation trials. FK506 and CsA, although structurally unrelated, appear to target similar signal transduction pathways in hematopoietic cells by inhibiting the action of calcineurin, a serine/threonine phosphatase. A structural analog of FK506, rapamycin, inhibits cellular function by a different molecular mechanism. These agents have advanced our understanding of signal transmission pathways in lymphocyte activation.

FK506 and cyclosporin, molecular probes for studying intracellular signal transduction

The immunosuppressants cyclosporin and FK506 block the calcium-dependent signal-transduction pathway emanating from the T-cell receptor, thereby inhibiting the activation of helper T cells. Using these drugs as probes, chemists and biologists have uncovered several intracellular signaling molecules bridging the generation of second-messenger Ca2+ ion and the transcriptional activation of IL-2, among which are calmodulin, calcineurin and the nuclear factor of activated T cells (NF-AT). Hence, Ca2+ binds to calmodulin, leading to the binding of calmodulin to calcineurin; the activated calcineurin, in turn, may dephosphorylate the cytoplasmic subunit of NF-AT, resulting in its translocation from the cytoplasm into the nucleus to form a competent transcriptional activator. As described by Jun Liu these drugs manifest their effects in an unprecedented fashion. They do not directly intercept intracellular signaling molecules. Instead, they form tight complexes with two different classes of abundant cytosolic receptors called immunophilins upon entering the cell, and consequently inhibit their peptidyl prolyl cis-trans isomerase activities. The two structurally distinct immunophilin-drug complexes bind to, and inhibit, the phosphatase activity of calcineurin.

FK506 and ciclosporin: molecular probes for studying intracellular signal transduction

The immunosuppressants ciclosporin and FK506 block the Ca(2+)-dependent signal-transduction pathway emanating from the T-cell receptor, thereby inhibiting the activation of helper T cells. Using these drugs as probes, chemists and biologists have uncovered several intracellular signalling molecules bridging the generation of second-messenger Ca2+ ions and the transcriptional activation of IL-2, among which are calmodulin, calcineurin and the nuclear factor of activated T cells (NF-AT). Hence, Ca2+ binds to calmodulin, leading to the binding of calmodulin to calcineurin; the activated calcineurin, in turn, may dephosphorylate the cytoplasmic subunit of NF-AT, resulting in its translocation from the cytoplasm into the nucleus to form a competent transcriptional activator. As described by Jun Liu, these drugs manifest their effects in an unprecedented fashion. They do not directly intercept intracellular signalling molecules. Instead, they form tight complexes with two different classes of abundant cytosolic receptors called immunophilins upon entering the cell, and consequently inhibit their peptidyl prolyl cis-trans isomerase activities. The two structurally distinct immunophilin-drug complexes bind to, and inhibit, the phosphatase activity of calcineurin.

Combination use of suboptimal dose of FK 506 and cyclosporine in canine lung transplantation

The immunosuppressive potency and the side effects of combination therapy with FK 506 and cyclosporine A were studied in dogs that had undergone lung transplantation. The animals were divided into four groups: group A (one third optimal FK 506 dose: FK 506, 0.03 mg/kg intramuscularly) (n = 5), group B (one third optimal cyclosporine dose: cyclosporine 6 mg/kg orally) (n = 5), group C (one third FK 506 and one third cyclosporine optimal doses): FK 506, 0.03 mg/kg intramuscularly plus cyclosporine 6 mg/kg orally) (n = 5), and group D (half FK 506 plus half cyclosporine optimal doses: FK 506, 0.05 mg/kg intramuscularly, plus cyclosporine, 10 mg/kg orally) (n = 10). Assessments including chest x-ray film, fiberoptic bronchoscopy, hematologic and biochemical tests, FK 506 and cyclosporine blood trough level measurement, right pulmonary artery occlusion test, and histopathologic observations were performed. In group A two of five dogs survived 28 days and three died on postoperative days 7, 14, and 21. In group B one dog survived 28 days and four died on postoperative days 9 (two dogs), 14, and 21. Histologic examination showed severe rejection in both group A and group B. In group C all five dogs survived 28 days but showed mild rejection. In group D one dog died of intestinal bleeding on postoperative day 7 and nine survived 28 days. No pathologic changes were observed except in one case of mild rejection. The ventilation function of the transplanted lung was poor in groups A, B, and C but good in group D. No abnormal rise of FK 506 and cyclosporine trough levels was observed. There were no significant side effects and abnormal hematologic and biochemical data except in one dog in group D. We concluded (1) the combination of FK 506, 0.03 mg/kg, and cyclosporine, 6 mg/kg, is much more effective than either drug used singly, (2) the combination of FK 506, 0.05 mg/kg, and cyclosporine, 10 mg/kg, prevents rejection with tolerable side effects, and (3) no worse side effects are caused by combination therapy with FK 506 and cyclosporine than by either one used singly.

Molecular mechanisms of immunosuppression

The immunosuppressive drug cyclosporin A (CsA, Sandimmun, SIM) is currently being evaluated in a variety of autoimmune disorders with some remarkable successes. Despite the wide empiric application of CsA, the precise mechanism of action of this drug remains elusive. To identify the molecular mode of action of CsA in the process of T cell activation, we have compared the biological profile of cyclophilin-binding cyclosporin analogues (CBCA), which lack immunosuppressive properties, with CsA. We have found that CsA binding to its intracellular receptor (cyclophilin) is required but not sufficient for immunosuppression. Moreover, inhibition of the peptidyl-prolyl cis-trans isomerase activity of cyclophilin does not seem to be relevant for the inhibitory effects of CsA. In analogy to the immunosuppressants FK506 and rapamycin, a specific structure at the 'effector' domain of the CsA molecule different from the immunophilin 'binding' domain determines the biological activity. Overall, a significant understanding of the structure-activity relationship of CsA has emerged. This will have a major impact on the identification of the precise mechanism of action of CsA and its side effects in the process of immunosuppression.