Positive effect on T-cell regulatory apoptosis by mycophenolate mofetil

Challenges and opportunities in achieving effective regulatory T cell therapy in autoimmune liver disease

Autoimmune liver diseases (AILD) include autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). These immune-mediated liver diseases involve a break down in peripheral self-tolerance with largely unknown aetiology. Regulatory T cells (Treg) are crucial in maintaining immunological tolerance. Hence, Treg immunotherapy is an attractive therapeutic option in AILD. Currently, AILD do not have a curative treatment option and patients take life-long immunosuppression or bile acids to control hepatic or biliary inflammation. Clinical investigations using good manufacturing practice (GMP) Treg in autoimmune liver disease have thus far demonstrated that Treg therapy is safe and that Treg migrate to inflamed liver tissue. For Treg immunotherapy to achieve efficacy in AILD, Treg must be retained within the liver and maintain their suppressive phenotype to dampen ongoing immune responses to hepatocytes and biliary epithelium. Therefore, therapeutic Treg subsets should be selected for tissue residency markers and maximal functionality. Optimisation of dosing regime and understanding longevity of Treg in vivo are critical to successful Treg therapy. It is also essential to consider combination therapy options to complement infused Treg, for instance low-dose interleukin-2 (IL-2) to support pre-existing and infused Treg survival and suppressive function. Understanding the hepatic microenvironment in both early- and late-stage AILD presents significant opportunity to better tailor Treg therapy in different patient groups. Modification of a hostile microenvironment to a more favourable one either prior to or during Treg therapy could enhance the efficacy and longevity of infused GMP-Treg. Applying recent technology to discovery of autoantigen responses in AILD, T cell receptor (TCR) sequencing and use of chimeric antigen receptor (CAR) technology represents the next frontier for disease-specific CAR-Treg therapies. Consideration of all these aspects in future trials and discovery research would position GMP Treg immunotherapy as a viable personalised-medicine treatment option for effective control of autoimmune liver diseases.

New Insights into the Treatment of Glomerular Diseases: When Mechanisms Become Vivid

Treatment for glomerular diseases has been extrapolated from the experience of other autoimmune disorders while the underlying pathogenic mechanisms were still not well understood. As the classification of glomerular diseases was based on patterns of juries instead of mechanisms, treatments were typically the art of try and error. With the advancement of molecular biology, the role of the immune agent in glomerular diseases is becoming more evident. The four-hit theory based on the discovery of gd-IgA1 gives a more transparent outline of the pathogenesis of IgA nephropathy (IgAN), and dysregulation of Treg plays a crucial role in the pathogenesis of minimal change disease (MCD). An epoch-making breakthrough is the discovery of PLA2R antibodies in the primary membranous nephropathy (pMN). This is the first biomarker applied for precision medicine in kidney disease. Understanding the immune system’s role in glomerular diseases allows the use of various immunosuppressants or other novel treatments, such as complement inhibitors, to treat glomerular diseases more reasonable. In this era of advocating personalized medicine, it is inevitable to develop precision medicine with mechanism-based novel biomarkers and novel therapies in kidney disease.

Successful mycophenolate mofetil treatment of a patient with severe steroid-refractory hepatitis evoked by nivolumab plus ipilimumab treatment for relapsed bladder cancer

Mycophenolate mofetil resulted in rapid improvement of steroid-refractory immune-related adverse event hepatitis, induced by nivolumab plus ipilimumab.

Delay expression of NKp30 on NK cells correlates with long-term mycophenolate mofetil treatment and higher EBV viremia post allogenic hematological stem cells transplantation

Mycophenolate mofetil (MMF) is an immunosuppressive agent that is widely used in graft-versus-host disease prophylaxis because of its inhibitory function on T cells and B cells. However, the effect of MMF on natural killer cell reconstitution after allogenic hematological transplantation is largely unknown. The present study examined the effects of different MMF administration durations after haploidentical allo-HSCT on NK cell reconstitution. Ninety patients were enrolled in this study and defined into two groups in term of MMF duration. We found that MMF patients in the long-term MMF group were associated with a poor reconstitution of NK cells and a significantly lower cytotoxicity from day 30 to day 180 post-transplantation. Especially, the long-term MMF group inhibits reconstitution of NKp30 NK subsets, which correlated with higher risk of EBV viremia. Multivariate analysis showed that a better reconstitution of NKp30 cells was associated with lower EBV viremia (HR0.957, p = .04). In vitro experiments demonstrated that the active metabolite of MMF, mycophenolic acid (MPA), inhibited the proliferation and cytotoxicity of NK cells from healthy donors or patients at day 30 post-transplantation. In summary, our findings demonstrated that long-term MMF administration delayed the quality and quantity of NK cells, especially NKp30 subpopulations, which was associated with decreased EBV viremia post allogeneic HSCT.

Mycophenolic acid induces senescence of vascular precursor cells

OBJECTIVE

Endothelial dysfunction is central to the pathogenesis of many rheumatic diseases, typified by vascular inflammation and damage. Immunosuppressive drugs induce disease remission and lead to improved patient survival. However, there remains a higher incidence of cardiovascular disease in these patients even after adequate disease control. The purpose of this study was to determine the effect of mycophenolic acid (MPA), a commonly used immunosuppressive drug in rheumatology, on blood vessel or circulating endothelial colony forming cell number and function.

METHODS

We tested whether mycophenolic acid exerts an inhibitory effect on proliferation, clonogenic potential and vasculogenic function of endothelial colony forming cell. We also studied potential mechanisms involved in the observed effects.

RESULTS

Treatment with MPA decreased endothelial colony forming cell proliferation, clonogenic potential and vasculogenic function in a dose-dependent fashion. MPA increased senescence-associated β-galactosidase expression, p21 gene expression and p53 phosphorylation, indicative of activation of cellular senescence. Exogenous guanosine supplementation rescued diminished endothelial colony forming cell proliferation and indices of senescence, consistent with the known mechanism of action of MPA.

CONCLUSION

Our findings show that clinically relevant doses of MPA have potent anti-angiogenic and pro-senescent effects on vascular precursor cells in vitro, thus indicating that treatment with MPA can potentially affect vascular repair and regeneration. This warrants further studies in vivo to determine how MPA therapy contributes to vascular dysfunction and increased cardiovascular disease seen in patients with inflammatory rheumatic disease.

Effect of mycophenolic acid in experimental, nontransplant glomerular diseases: new mechanisms beyond immune cells

Mycophenolic acid (MPA) was introduced into clinical practice as immunosuppressive drug therapy to prevent allograft rejection. Since then, its clinical application has widened. Our goal was to review the lessons learned from experimental nontransplant glomerular disease models on the mechanisms of MPA therapy. T and B lymphocytes are preferentially dependent on de novo purine synthesis. By inhibiting the rate-limiting enzyme of de novo purine synthesis, MPA depletes the pool of deoxyguanosine triphosphate (dGTP) and inhibits proliferation of these immune cells. Furthermore, MPA can also induce apoptosis of immune cells and is known to inhibit synthesis of fucose- and mannose-containing membrane glycoproteins altering the surface expression and binding ability of adhesion molecules. However, MPA exerts a direct effect also on nonimmune cells. Mesangial cells are partially dependent on de novo purine biosynthesis and are thus susceptible to MPA treatment. Additionally, MPA can inhibit apoptosis in podocytes and seems to be beneficial in preserving the expression of nephrin and podocin, and by attenuation of urokinase receptor expression leads to decreased foot-process effacement. In summary, our manuscript sheds light on the molecular mechanisms underlying the antiproteinuric effect of MPA. Overall, MPA is an excellent treatment option in many immunologic glomerulopathies because it possesses immunosuppressive properties, has a remarkable effect on nonimmune cells and counteracts the proliferation of mesangial cells, expansion of mesangial matrix, and foot-process effacement of podocytes combined with a low systemic toxicity.

Mycophenolate mofetil as an immunomodulatory silver bullet in atherogenesis?

Atherosclerotic vascular disease is a chronic disorder of the vasculature with a substantial impact on society. Although the availability of statins has represented an unparalleled improvement in the treatment of patients with such cardiovascular disease, even more effective measures are required to reverse this disorder with a continuously growing incidence. The classification of atherosclerosis as an inflammatory disorder has prompted the hypothesis that immunomodulation could comprise a novel anti-atherosclerotic strategy. Mycophenolate mofetil (MMF) has various anti-atherogenic effects on major components of the atherosclerotic plaque such as T-lymphocytes, monocytes/macrophages and the endothelium. MMF can inhibit leukocyte recruitment to the subendothelium and the subsequent reduced activation of leukocytes will translate into attenuation of subendothelial crosstalk between T-cells and macrophages. This cascade of events will interrupt the self-perpetuating pro-inflammatory environment within the arterial wall, the hallmark of atherosclerotic vascular disease.

In Vitro Influence of Mycophenolic Acid on Selected Parameters of Stimulated Peripheral Canine Lymphocytes

Mycophenolic acid (MPA) is an active metabolite of mycophenolate mofetil, a new immunosuppressive drug effective in the treatment of canine autoimmune diseases. The impact of MPA on immunity is ambiguous and its influence on the canine immune system is unknown. The aim of the study was to determine markers of changes in stimulated peripheral canine lymphocytes after treatment with MPA in vitro. Twenty nine healthy dogs were studied. Phenotypic and functional analysis of lymphocytes was performed on peripheral blood mononuclear cells cultured with mitogens and different MPA concentrations– 1 μM (10⁻³ mol/m³), 10 μM or 100 μM. Apoptotic cells were detected by Annexin V and 7-aminoactinomycin D (7-AAD). The expression of antigens (CD3, CD4, CD8, CD21, CD25, forkhead box P3 [FoxP3] and proliferating cell nuclear antigen [PCNA]) was assessed with monoclonal antibodies. The proliferation indices were analyzed in carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled cells. All analyses were performed using flow cytometry. The influence of MPA on apoptosis was dependent on the mechanism of cell activation and MPA concentration. MPA caused a decrease in the expression of lymphocyte surface antigens, CD3, CD8 and CD25. Its impact on the expression of CD4 and CD21 was negligible. Its negative influence on the expression of FoxP3 was dependent on cell stimulation. MPA inhibited lymphocyte proliferation. In conclusion, MPA inhibited the activity of stimulated canine lymphocytes by blocking lymphocyte activation and proliferation. The influence of MPA on the development of immune tolerance–expansion of Treg cells and lymphocyte apoptosis–was ambiguous and was dependent on the mechanism of cellular activation. The concentration that MPA reaches in the blood may lead to inhibition of the functions of the canine immune system. The applied panel of markers can be used for evaluation of the effects of immunosuppressive compounds in the dog.

Mycophenolate mofetil for the induction and maintenance treatment of lupus nephritis

Mycophenolate mofetil (MMF) inhibits purine synthesis by inhibiting inosine-5’-monophosphate dehydrogenase. Since 1995, it has been approved in the USA for the prevention of allograft rejection in solid organ transplant patients. In the last two decades, it has been frequently used as an immunosuppressive therapy for numerous autoimmune conditions including lupus nephritis. Management of lupus nephritis has been advanced by well-designed randomized clinical trials establishing MMF as a viable alternative to established therapies such as pulse intravenous cyclophosphamide in selected patients. This article outlines the pharmacologic properties of MMF and summarizes recent randomized clinical trials in lupus nephritis.

The evolving role of mTOR inhibition in transplantation tolerance

The mammalian target of rapamycin (mTOR) plays a key role in the immune response. mTOR inhibitors suppress T cell activation and proliferation and are effective immunosuppressants. Today there is growing interest in their potential role in inducing tolerance after transplantation. mTOR inhibitors induce anergy in naïve T cells, promote the expansion of regulatory T cells, and inhibit the maturation of dendritic cells, thus promoting immunologic tolerance. Here we review the mechanisms by which mTOR inhibitors promote tolerance. We discuss the clinical relevance of these mechanisms and suggest how they might be used in the design of future protocols to induce tolerance.

In vitro and in vivo immunomodulatory effects of cobalt protoporphyrin administered in combination with immunosuppressive drugs

BACKGROUND

Immunosuppressive strategies are designed to take advantage of potential synergies between drugs to possibly decrease the risk of side-effects. In the present study, the ability of Cobalt protoporphyrin (CoPP) to potentiate the effect of the immunosuppressive drugs mycophenolate sodium (MPS) or cyclosporin A (CsA) was explored in vitro and in vivo.

METHODS

In vitro analyses of proliferation and apoptosis were performed on primate T cell cultures, following incubation with the immunosuppressive drugs MPS or CsA, alone or in combination with CoPP. In vivo the effect of CoPP and CsA combination therapy was assessed in a rat heterotopic cardiac allotransplantation model.

RESULTS

In vitro results suggest that co-administration of CoPP with CsA or MPS increases immunosuppressive effects of these drugs when combined with CoPP. In particular, the co-administration of CoPP with CsA resulted in the synergistic induction of lymphocyte apoptosis. In vivo, animals immunosuppressed with CsA (1.5 mg/kg) or CoPP (20 mg/kg) alone, had a median survival of 7 or 8 days, respectively. In contrast, animals immunosuppressed with CsA (1.5 mg/kg) combined with CoPP (20 mg/kg) had significantly prolonged median survival (12 days), compared to recipients treated with CsA or CoPP alone (p<0.05).

CONCLUSION

Our in vitro and in vivo studies demonstrate that CoPP can potentiate the immunomodulatory effects of CsA, ultimately extending allograft survival.

Mycophenolic acid and intravenous immunoglobulin exert an additive effect on cell proliferation and apoptosis in the mixed lymphocyte reaction

BACKGROUND

Intravenous immunoglobulin (IVIG) has known immunomodulatory effects in autoimmune diseases and transplantation and is commonly used in desensitization protocols and for treatment of antibody-mediated rejection (AMR). IVIG inhibits the MLR and induces apoptosis in immune cells. Mycophenolate mofetil inhibits immune cell proliferation and is an effective immunsuppressive agent. Here, we examined the possible synergistic effects of combined MMF and IVIG on cell proliferation and apoptosis induction in the MLR.

METHODS

Two-way MLRs were performed with mycophenolic acid (MPA), IVIG and both in combination. Cell proliferation and apoptosis were detected by 3H-thymidine incorporation and Annexin flow cytometry, respectively.

RESULTS

IVIG (1-10mg/ml) or MPA (0.01-0.25 microg/ml) alone inhibited cell proliferation in the MLR in a dose-dependent manner. MPA at 0.01-0.03 microg/ml showed minimal inhibition, but the addition of 5 and 10mg/ml IVIG increased inhibition significantly (p<0.05) to 43% and 64%, respectively. Annexin V positive cell number was significantly higher in IVIG (5mg/ml) treated CD19+ cells (68+/-13% vs. 43+/-12%, p=0.001) compared to untreated cells and to a lesser degree in CD3+ cells (29+/-7% vs. 25+/-10 %, p=0.02). MPA (0.25-10 microg/ml) alone neither induced nor inhibited apoptosis. Addition of MPA had no effect on apoptosis induced by IVIG.

CONCLUSION

1) Combining low concentrations of IVIG (5-10 mg/ml) and MPA (0.01-0.03 microg/ml)has an additive effect on inhibition of cell proliferation in the MLR. 2) MPA alone neither induces nor inhibits apoptosis in T or B cells in the MLR, and has no effect on apoptosis induced by IVIG. These in vitro observations may have implications for modification of therapeutic approaches to protocols utilizing IVIG for desensitization and immune modulation.

Mycophenolate mofetil: effects on cellular immune subsets, infectious complications, and antimicrobial activity

Mycophenolate mofetil (MMF) is one of the most frequently used immunosuppressive drugs in solid organ transplant recipients. MMF is an inhibitor of inosine-5'-monophosphate, and is able to preferentially inhibit B-cell and T-cell function. The immunosuppressive abilities of MMF have made it one of the most successful anti-rejection drugs in transplant patients, but patients also appear to have increased susceptibility to infections, specifically cytomegalovirus and BK virus. Despite its association with an increased risk of infection, MMF has also exhibited antimicrobial activity against pathogens including hepatitis C, Pneumocystis jirovecii, and human immunodeficiency virus. A thorough understanding of the functions of MMF on the immune system and interaction with infectious pathogens could be helpful in implementing preventative strategies against opportunistic infections in transplant patients.

Manipulating the immune system for anti-tumor responses and transplant tolerance via mixed hematopoietic chimerism

SUMMARY

Stem cells (SCs) with varying potentiality have the capacity to repair injured tissues. While promising animal data have been obtained, allogeneic SCs and their progeny are subject to immune-mediated rejection. Here, we review the potential of hematopoietic stem cells (HSCs) to promote immune tolerance to allogeneic and xenogeneic organs and tissues, to reverse autoimmunity, and to be used optimally to cure hematologic malignancies. We also review the mechanisms by which hematopoietic cell transplantation (HCT) can promote anti-tumor responses and establish donor-specific transplantation tolerance. We discuss the barriers to clinical translation of animal studies and describe some recent studies indicating how they can be overcome. The recent achievements of durable mixed chimerism across human leukocyte antigen barriers without graft-versus-host disease and of organ allograft tolerance through combined kidney and bone marrow transplantation suggest that the potential of this approach for use in the treatment of many human diseases may ultimately be realized.

Mycophenolate mofetil for non-renal manifestations of systemic lupus erythematosus: a systematic review

OBJECTIVE

To summarize the evidence for the use of mycophenolate mofetil (MMF) in non-renal manifestations of systemic lupus erythematosus (SLE).

METHODS

Treatment trials in human SLE from 1990 to 2006 that have been published in the English literature were searched by Medline using the keywords 'lupus', 'mycophenolate', 'neuropsychiatric', 'neurological', 'hematological', 'dermatological', 'cutaneous', 'skin', 'hemolytic' and 'thrombocytopenia'. Laboratory studies were excluded.

RESULTS

Twenty relevant studies were summarized. All were case series or open-labelled trials. The main indications for MMF were refractory haematological and dermatological lupus. Data regarding MMF in neuropsychiatric SLE were scant. Favourable results were reported with haematological disease. Evidence regarding the efficacy of MMF in refractory lupus skin lesions was conflicting. The efficacy of MMF in neuropsychiatric lupus was only modest and could not be separated from that of concomitant therapies. In one uncontrolled study, MMF was reported to be effective in preventing clinical flares in patients with persistently active serological markers. MMF was well tolerated in these reports.

CONCLUSIONS

Limited evidence suggests that MMF may be effective in refractory haematological and dermatological manifestations of SLE. Because of the possibility of publication bias, the efficacy of MMF in these manifestations has to be confirmed with controlled trials. The efficacy of MMF in neuropsychiatric SLE is unproven and should be restricted to those patients who are refractory and intolerant to, or reluctant for, cyclophosphamide. Finally, the current level of evidence does not support treating serology alone in SLE by MMF.

Current and emerging strategies for the management of sarcoidosis

Sarcoidosis is a systemic inflammatory disorder of unknown etiology. Although any organ may be involved, the lungs are most frequently affected. The clinical course of the disease is highly variable, with up to two-thirds of untreated patients experiencing spontaneous remission within 12-24 months of onset of symptoms. When therapy is required, corticosteroids are considered standard, but studies demonstrating their ability to modify the long-term outcome in this disease are lacking. Often, the myriad of adverse side effects of corticosteroids necessitate the addition of immunosuppressants, cytotoxic agents or biologic therapies to maintain disease remission. Unfortunately, optimal therapeutic regimens have not been described. Patients who do not respond to therapy often experience progressive fibrotic changes and end-organ damage, which ultimately may result in significant morbidity or death. Agents commonly used to treat patients with sarcoidosis and emerging therapeutic options are discussed.

The Influence of Immunosuppressive Drugs on T- and B-cell Apoptosis via p53-Mediated Pathway In Vitro and In Vivo

BACKGROUND

This study was designed to assess the effects of calcineurin and inosine-5-monophosphate-dehydrogenase inhibitors on p53-mediated-apoptosis in T- and B-cells in vitro and in human heart-transplanted recipients (HTx-R).

METHODS

For in vitro experiments, peripheral blood from healthy volunteers was collected and treated either with 1 microM cyclosporin A (CsA; n = 6), 10 microM mycophenolic acid (MPA; n = 6) or 100 nM tacrolimus (TRL; n = 6). For the second part, peripheral blood was collected from HTx-R undergoing CsA-MPA (n = 11) or TRL-MPA (n = 11) therapy before (0 hr) and after (2 hr) acute drug application and from healthy volunteers (n = 11) without drug therapy. Whole blood (part 1+2) was stimulated (24 hr) with eight different concentrations of actinomycin-D (0-800 nM), an apoptosis inductor acting via p53-pathway. Apoptotic lymphocytes were measured by TUNEL and expression of Annexin-V using FACS. Drug effects were calculated by taking the effects of actinomycin-D as baseline values.

RESULTS

In vitro drug treatment with CsA, MPA, and TRL significantly (P < 0.05) decreased the apoptotic effect of actinomycin-D in T-cells in a noncompetitive manner. In HTx-R undergoing drug therapy, there was a similar antiapoptotic effect observed in both T- and B-cells (P < 0.05). Differences between 0 hr and 2 hr after acute drug application did not exist. Apoptosis induced by actinomycin-D can be completely blocked by caspase-inhibitor zVAD-FMK.

CONCLUSION

Our results suggest that, in vitro and in HTx-R, an inhibition of calcineurin and inosine-5-monophosphate-dehydrogenase by CsA, TRL, or MPA lead to an inhibition of T-and B-cell apoptosis via p53-pathway. This assay may be helpful to provide insights into mechanisms of immunosuppressive drugs in regulation of apoptosis in lymphocytes.

Apoptosis and Caspase-3 in Long-Term Renal Ischemia/Reperfusion Injury in Rats and Divergent Effects of Immunosuppressants

BACKGROUND

Caspase-3 plays a key role in apoptosis, but the involvement of apoptosis and caspase-3 in mediating long-term ischemia/reperfusion (I/R) and immunosuppressive injury are not fully defined. The present study was undertaken to investigate apoptosis and caspase-3 in a renal I/R injury rat model with or without immunosuppression.

METHODS

The right renal pedicle was clamped for 45 minutes and left nephrectomy was induced. Cyclosporin A (CsA), tacrolimus (Tac), rapamycin (Rap), or mycophenolate mofetil (MMF) were administered daily. Animals were killed at 16 weeks, and the levels of apoptosis (with in situ end-labeling fragmented DNA), caspase-3 protein (with immunohistochemistry, Western blotting, and activity assay), and messenger RNA (mRNA; with quantitative reverse-transcriptase polymerase chain reaction) were evaluated.

RESULTS

Kidneys with I/R injury showed increased apoptosis in tubular and interstitial areas compared with control kidneys. Tacrolimus, Rap, and MMF significantly reduced apoptosis, but CsA did not. Distribution of full-length caspase-3 widened in I/R-injured kidneys from normal distal tubules and collecting ducts to dilated proximal tubules and expanded interstitium, whereas active caspase-3 was mainly scattered in damaged tubules and interstitium. Active caspase-3 staining and 24-kDa active caspase-3 protein was enhanced in I/R-injured and CsA-treated kidneys, but decreased by Tac, Rap, and MMF. These results were also consistent with changes in caspase-3 activity. Although caspase-3 mRNA levels were significantly increased in uninephrectomy and I/R-injured kidneys, they were not significantly affected by the immunosuppressants. In addition, all changes detected were positively correlated with renal structure and function.

CONCLUSION

Apoptosis and caspase-3 are not only involved in the long-term renal I/R injury, but also mediate the divergent effects of immunosuppression in this model.

Mechanisms of action of mycophenolate mofetil in preventing acute and chronic allograft rejection

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), an inhibitor of inosine-5'-monophosphate dehydrogenase, has several immunosuppressant actions. MPA depletes guanosine and deoxyguanosine nucleotides preferentially in T and B lymphocytes, inhibiting proliferation and suppressing cell-mediated immune responses and antibody formation, major factors in acute and chronic rejection. MPA also can induce T-lymphocyte apoptosis. MPA suppresses dendritic cell maturation and can induce human monocyte-macrophage cell line differentiation, decreasing the expression of interleukin (IL)-1 and enhancing expression of the IL-1 receptor antagonist. In addition, MPA inhibits adhesion molecule glycosylation and expression and lymphocyte and monocyte recruitment. Activated macrophages produce nitric oxide (NO) and superoxide, which combine to generate tissue-damaging peroxynitrite. MPA depletes tetrahydrobiopterin and decreases NO production by inducible NO synthase without affecting constitutive NO synthase activity. By these mechanisms, MMF exerts anti-inflammatory activity, which could attenuate both acute and chronic rejection. Unlike calcineurin inhibitors, MMF is nonnephrotoxic and does not induce transforming growth factor-beta production, which is fibrogenic. MMF inhibits arterial smooth muscle cell proliferation, a contributor to graft proliferative arteriopathy, and does not increase blood pressure, cholesterol, or triglyceride levels. By decreasing high-density lipoprotein oxidation and macrophage recruitment, MMF also may delay onset/progression of graft atherosclerosis. Thus, MMF may prevent chronic rejection by several mechanisms. MMF activity is synergistic with that of other agents such as valganciclovir for treating cytomegalovirus infection. MMF also has synergistic activity with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists in the treatment of some nephropathies in experimental animals. This combination may prevent progression toward end-stage renal disease in humans with chronic allograft, lupus, and diabetic nephropathies.

Morphological Findings in Lymphatic Tissues of Sheep Following Oral Application of the Immunosuppressive Mycotoxin Mycophenolic Acid

Mycophenolic acid (MPA) is applied in immunosuppressive therapy after organ transplantation. As a common contaminant in silage, this substance is also frequently fed to sheep unintentionally. In this study, the effect of MPA on the immune system of sheep was examined. Four groups of 9 sheep each were fed 0, 0.5, 1.2, or 5 mg of MPA per kg body weight per day for 6 weeks. Then, the animals were slaughtered and various organs were examined macroscopically, histologically, and immunohistochemically. No effect of MPA on general health was detected. With increasing dose of MPA, germinal centres in the retropharyngeal lymph nodes displayed an activated morphology with numerous centroblasts. In the highest dose group, the sheep showed shrinkage of thymic lobules. The numbers of IgG or IgM positive plasma cells decreased in the ileum with increasing MPA-doses. These results suggest, that MPA in a high concentration may affect the morphology of immune organs of sheep.

Augmentation of T-cell apoptosis by immunosuppressive agents

The regulatory benefit of apoptosis (activation-induced cell death, AICD) in T cells can be influenced by immunosuppressive agents. We examined this for mycophenolate mofetile (MMF, using it's active metabolite, mycophenolate (MPA)) compared with rapamycin (RAPA) and the calcineurin inhibitors (CI) cyclosporin (CYA) and FK506 (FK). Pure T cells from peripheral blood leucocytes (PBL) were stimulated by anti-CD3 plus anti-CD28. Cell division (sequential cohort reduction in carboxyflourescein diacetate succinimidyl ester, CFSE) was used to measure proliferation and determine status of different cell generations without or with added drug at 4 d. Apoptosis was measured by Annexin V staining of activated cells using flow cytometry. We confirmed in this stringent system the inhibition of AICD by CI and showed that RAPA is intermediate and MPA most effective in this potentiation of AICD.

Measurement of mycophenolate mofetil effect in transplant recipients

BACKGROUND

Immunosuppression involves the nature of the immunosuppressive agents and individual differences in patient factors. We investigated whether the effect of mycophenolate mofetil (MMF) is measurable using an in vitro measure of immunocompetence and related its effects to cyclosporine (CsA) in vitro.

METHODS

Liver or kidney transplant recipients receiving prednisone; CsA or tacrolimus; and MMF, azathioprine (AZA), or neither, were studied. Immunocompetence was assessed by one-way mixed lymphocyte culture using patients' peripheral blood leukocytes (PBL) and three validated stimulators. The effect of immunosuppressive agents added in vitro on normal PBL stimulation by Staphylococcus enterotoxin B was determined by the carboxyfluorescein diacetate succinimidyl ester measurement of division.

RESULTS

Patients receiving MMF had an average immunocompetence level of 12+/-23, compared with 39.7+/-65 and 25.5+/-42 for those receiving AZA or neither AZA nor MMF, respectively. Thus, there was an approximately 80% suppression of the response in the MMF group. Assessment of normal cell division revealed that CsA allowed multiple cell generations but suppressed the numbers of cells in each, whereas MMF blocked proliferation into subsequent generations. Addition of clinically relevant levels of mycophenolic acid, the active agent for MMF, added to more moderate levels of CsA, was required to achieve greater than 80% suppression, consistent with the degree of immunocompetence depression measured in patients.

CONCLUSIONS

These data provide the novel finding that the effect of MMF treatment on patients is measurable in their PBL as decreased immunocompetence in vitro. The effect of MMF on normal PBL approximates the 80% inhibition that we found in patients. Moreover, the effect of MMF on cell division provides a rationale for the superior effectiveness of regimens including MMF.