Differences in Type 1 and Type 2 intracytoplasmic cytokines, detected by flow cytometry, according to immunosuppression (cyclosporine A vs. tacrolimus) in stable renal allograft recipients

Targeting CaN/NFAT in Alzheimer's brain degeneration

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive loss of cognitive functions. While the exact causes of this debilitating disorder remain elusive, numerous investigations have characterized its two core pathologies: the presence of β-amyloid plaques and tau tangles. Additionally, multiple studies of postmortem brain tissue, as well as results from AD preclinical models, have consistently demonstrated the presence of a sustained inflammatory response. As the persistent immune response is associated with neurodegeneration, it became clear that it may also exacerbate other AD pathologies, providing a link between the initial deposition of β-amyloid plaques and the later development of neurofibrillary tangles. Initially discovered in T cells, the nuclear factor of activated T-cells (NFAT) is one of the main transcription factors driving the expression of inflammatory genes and thus regulating immune responses. NFAT-dependent production of inflammatory mediators is controlled by Ca2+-dependent protein phosphatase calcineurin (CaN), which dephosphorylates NFAT and promotes its transcriptional activity. A substantial body of evidence has demonstrated that aberrant CaN/NFAT signaling is linked to several pathologies observed in AD, including neuronal apoptosis, synaptic deficits, and glia activation. In view of this, the role of NFAT isoforms in AD has been linked to disease progression at different stages, some of which are paralleled to diminished cognitive status. The use of classical inhibitors of CaN/NFAT signaling, such as tacrolimus or cyclosporine, or adeno-associated viruses to specifically inhibit astrocytic NFAT activation, has alleviated some symptoms of AD by diminishing β-amyloid neurotoxicity and neuroinflammation. In this article, we discuss the recent findings related to the contribution of CaN/NFAT signaling to the progression of AD and highlight the possible benefits of targeting this pathway in AD treatment.

Acute Versus Chronic Administration of Calcineurin-Inhibitors Differentially Affect T-Cell Function

BACKGROUND

Calcineurin-inhibitors (CNI) are used in renal transplant patients (RTX) to prevent rejection. CNI mainly suppress T-cell mediated immunity but very little is known about the impact of long-term treatment with CNI on T-cell function.

OBJECTIVE

We investigated the immunological effects of long-term CNI intake in RTX patients in comparison to short-term CNI administration in healthy controls (HC).

METHODS

Blood was drawn from 30 RTX patients with long-term CNI treatment. In addition, blood was sampled from HC with short-term CNI treatment (four dosages) before the first and 2 hours after the last CsA intake. T-cells were analyzed for cytokine production, proliferation, and CD25 expression.

RESULTS

Short-term CNI reduced T-cell derived IL-2 and IFNγ as well as T-cell proliferation in HC. IFNγ was not suppressed in patients with long-term CNI treatment. IL-2 production, CD25 expression, and T-cell proliferation were enhanced in long-term CNI patients.

CONCLUSION

Suppression of IFNγ/IL-2 and T-cell proliferation is weaker during long-term CNI treatment in patients compared to short-term treatment in healthy subjects. Enhanced CD25 expression may lower the threshold for T-cell activation during long-term CNI treatment.

Application of Operational Tolerance Signatures Are Limited by Variability and Type of Immunosuppression in Renal Transplant Recipients: A Cross-Sectional Study

Supplemental digital content is available in the text.

Background

Renal transplant recipients (RTR) frequently develop complications relating to chronic immunosuppression. Identifying RTR who could safely reduce immunosuppression is therefore highly desirable. We hypothesized that “signatures” described in RTR who have stopped immunosuppression but maintained stable graft function (“operational tolerance”) may enable identification of immunosuppressed RTR who are candidates for immunosuppression minimization. However, the effect of immunosuppression itself on these signatures and circulating B-cell populations is currently unknown.

Methods

We undertook a cross-sectional study of 117 RTR to assess the effect of immunosuppression upon circulating B cell populations, humoral alloresponse and 2 previously published “signatures” of operational tolerance.

Results

Immunosuppression associated with alterations in both published “signatures.” Azathioprine associated with a decrease in transitional and naive B-cell numbers and calcineurin inhibition associated with an increase in the number of circulating plasmablasts. However, only azathioprine use associated with the presence of donor-specific anti-HLA IgG antibodies. Calcineurin inhibition associated with an increase in total serum IgM but not IgG. Data were corrected for age, time since last transplant, and other immunosuppression.

Conclusions

Current signatures of operational tolerance may be significantly affected by immunosuppressive regimen, which may hinder use in their current form in clinical practice. Calcineurin inhibition may prevent the development of long-lasting humoral alloresponses, whereas azathioprine therapy may be associated with donor specific antibody development.

Asymptomatic De Novo Inflammatory Bowel Disease Late After Liver Transplantation for Primary Sclerosing Cholangitis: A Case Report

Guidelines recommend colonoscopy screening for possible asymptomatic inflammatory bowel disease (IBD) in all patients diagnosed with primary sclerosing cholangitis (PSC). PSC-IBD warrants regular dysplasia-surveillance colonoscopy. However, no consensus exists regarding follow-up colonoscopy in PSC patients without IBD who remain asymptomatic. We describe a 43-year-old female who had undergone liver transplantation (LT) due to advanced PSC. Previous colonoscopies had been normal. The post-transplantation course was uneventful, with no rejections and signs of PSC recurrence. Immunosuppression was by tacrolimus monotherapy. She was asymptomatic with normal inflammation markers. A protocol colonoscopy, performed as general dysplasia surveillance 8 years post-transplantation, revealed mucopurulent-covered small superficial ulcerations and erythema diffusely distributed from the cecal to sigmoid colon with intervening normal mucosa and rectal sparing. Histologic examination showed patchy chronic colitis with crypt architectural distortion and mild-moderate inflammation activity. Infection samples were negative. Findings complied with de novo IBD, type unclassified. In conclusion, the link between PSC and clinically silent IBD may manifest after the PSC diagnosis and even several years after LT. Given the increased colorectal cancer risk associated with PSC, IBD, and LT, repeat colonoscopy might be warranted in PSC patients without IBD at initial assessment, and also after LT.

High expression of CD38, CD69, CD95 and CD154 biomarkers in cultured peripheral T lymphocytes correlates with an increased risk of acute rejection in liver allograft recipients

The mayor goal still outstanding into the solid organ transplantation field involves the search of surrogate biomarkers able to predict several clinical events, such as acute rejection (AR) or opportunistic infection. In the present multicenter study, a series of interesting surface antigens with important activator or inhibitory immune functions on cultured peripheral T cells were monitored in liver transplant recipients drawn at baseline and up to one year after transplantation. Sixty-four patients were included in the multicenter study during 3 years. Pre- and post-transplantation surface antigens levels displayed significant differences between AR and non acute rejection (NAR) groups, and also this differential expression was used to construct a risk predictive model based on a composite panel of outcome biomarkers (CD38, CD69, CD95 and CD154). The model was able to stratify these patients at high risk of AR. These preliminary results could provide basic information to improve the immunosuppressive treatment and it might better help to predict AR episodes.

De novo Crohn's disease following orthotopic liver transplantation: a case report and literature review

The development of de novo Crohn's disease (CD) after orthotopic liver transplantation (OLT) is rare, possibly due to the continuous use of immunosuppressive treatment. Although several cases of CD following OLT have been reported worldwide, there are currently so such cases in Japan. We herein report the case of a patient who newly developed CD after undergoing OLT for congenital biliary atresia. The patient subsequently underwent ileocecal resection and has since maintained clinical remission. This is the first report of this condition in Japan. We also review the literature concerning cases of de novo inflammatory bowel disease (IBD) developing after OLT, and discuss the causes of and role of immunosuppressive agents in treating IBD.

Clinical management of inflammatory bowel disease in the organ recipient

There was estimated a higher incidence of de novo inflammatory bowel disease (IBD) after solid organ transplantation than in the general population. The onset of IBD in the organ transplant recipient population is an important clinical situation which is associated to higher morbidity and difficulty in the medical therapeutic management because of possible interaction between anti-reject therapy and IBD therapy. IBD course after liver transplantation (LT) is variable, but about one third of patients may worsen, needing an increase in medical therapy or a colectomy. Active IBD at the time of LT, discontinuation of 5-aminosalicylic acid or azathioprine at the time of LT and use of tacrolimus-based immunosuppression may be associated with an unfavorable outcome of IBD after LT. Anti-tumor necrosis factor alpha (TNFα) therapy for refractory IBD may be an effective and safe therapeutic option after LT. The little experience of the use of biological therapy in transplanted patients, with concomitant anti-rejection therapy, suggests there be a higher more careful surveillance regarding the risk of infectious diseases, autoimmune diseases, and neoplasms. An increased risk of colorectal cancer (CRC) is present also after LT in IBD patients with primary sclerosing cholangitis (PSC). An annual program of endoscopic surveillance with serial biopsies for CRC is recommended. A prophylactic colectomy in selected IBD/PSC patients with CRC risk factors could be a good management strategy in the CRC prevention, but it is used infrequently in the majority of LT centers. About 30% of patients develop multiple IBD recurrence and 20% of patients require a colectomy after renal transplantation. Like in the liver transplantation, anti-TNFα therapy could be an effective treatment in IBD patients with conventional refractory therapy after renal or heart transplantation. A large number of patients are needed to confirm the preliminary observations. Regarding the higher clinical complexity of this subgroup of IBD patients, a close multidisciplinary approach between an IBD dedicated gastroenterologist and surgeon and an organ transplantation specialist is necessary in order to have the best clinical management of IBD after transplantation.

Inflammatory bowel disease and pregnancy: overlapping pathways

Several studies have reported on the association between inflammatory bowel disease (IBD) and adverse pregnancy outcomes, such as preterm birth. The exact mechanisms of action are unclear; however, several pathways and processes are involved in both IBD and pregnancy that may help explain this. In this review, we discuss the immune system's T helper cells and human leukocyte antigens, inflammation, its function, and the role of Toll-like receptors (TLRs), NOD-like receptors (NLRs), and prostaglandins in the inflammatory response. For each of these topics, we consider their involvement in IBD and pregnancy, and we speculate as to how they can lead to preterm birth. Finally, we review briefly corticosteroids, biologic therapies, and immunosuppressants for the treatment of IBD, as well as their safety in use during pregnancy, with special focus on preterm birth.

Clinical Significance of the Pharmacological Efficacy of Tacrolimus Estimated by the Lymphocyte Immunosuppressant Sensitivity Test (LIST) Before and After Renal Transplantation

The lymphocyte immunosuppressant sensitivity test (LIST) with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay procedure can predict the pharmacological efficacy of immunosuppressive agents. A previous study reported the pharmacological efficacy of tacrolimus evaluated by LIST just before renal transplantation significantly correlated with the incidence of acute rejection episodes. However, the pharmacological efficacy of tacrolimus has not been estimated after renal transplantation. Therefore, the present study evaluated the pharmacological efficacy of tacrolimus by LIST using the MTT assay procedure before and 1, 3, and 12 months after transplantation in 17 renal transplant recipients that received tacrolimus-based immunosuppressive therapy. The tacrolimus pharmacological efficacies before and after the procedure were also compared with incidence of acute rejection and cytomegalovirus (CMV) infection episodes. The individual values of tacrolimus 50% inhibition of lymphocyte proliferation (IC50) varied widely before transplantation, and the mean value of the IC50 was 126.4 ± 337.7 ng/ml. The patients were divided into two groups according to the tacrolimus IC50 values evaluated before transplantation. The rate of acute rejection episodes in the tacrolimus high-sensitivity group was significantly lower than that in the tacrolimus low-sensitivity group (p = 0.005). The tacrolimus IC50 deviation between patients expanded further at one and three months after surgery. However, the sensitivity deviation almost converged at 1 year after surgery. Moreover, the pharmacological efficacy of tacrolimus evaluated at 1, 3, and 12 months after transplantation did not significantly correlate with the incidence of acute rejection episodes. The pharmacological efficacies of tacrolimus evaluated at both before and after surgery were not significantly correlated with the episodes of CMV infection. These findings suggest that the pharmacological efficacy of tacrolimus evaluated with LIST before surgery is a useful biomarker for predicting the occurrence of acute allograft rejection in renal transplantation.

Review: Pharmacodynamic monitoring of immunosuppression in kidney transplantation

Advances in immunosuppressive therapies have improved kidney transplant outcomes. However, immunosuppressant drug-induced toxicities continue to reduce tolerability and impact patient and graft survival. A major ongoing challenge in kidney transplantation is to establish ways of tailoring immunosuppressant therapy so as to maintain efficacy while minimizing toxicity. Pharmacodynamic monitoring by direct measurement of immune cell function has the potential to personalize immunosuppression. The purpose of this review is to provide the clinician with an overview of the methodology and use of immune function monitoring in the field of kidney transplantation.

NFAT pulls the strings during CD4+ T helper cell effector functions

The Ca(2+) dependent transcription factor family known as nuclear factor of activated T cells (NFAT) has been shown to be important in T-cell immune responses. Because NFAT proteins have a weak DNA-binding capacity, they cooperate with other transcription factors at composite sites within the promoters of target genes. Recently, NFAT was shown to also be important for the induction of specific genetic programs that guide the differentiation and effector or regulatory activities of CD4(+) T helper subsets via the transcriptional regulation of their lineage-specific transcription factors, specifically T-bet (Th1), Gata3 (Th2), RORgammat (Th17), and Foxp3 (iTregs). In addition, the NFAT family governs the transcription of several signature cytokines, including their cytokine receptors. Subsequently, the integration of these complex intracellular signal transduction cascades is considered to critically determine the crosstalk between the T-cell receptor and receptors that are activated by both the adaptive and innate immune systems to determine pathways of T helper cell differentiation and function. Here, we carefully review the critical role of the established transcriptional partners and functional outcomes of these NFAT interactions in regard to the effector responses of these clinically relevant CD4(+) T helper subsets.

Improved outcome with immunosuppressive monotherapy after renal transplantation in Schimke-immuno-osseous dysplasia

SIOD is a multisystem disorder caused by a mutant chromatin remodelling protein. The main clinical findings are spondyloepiphyseal dysplasia with disproportionate growth restriction, defective cellular immunity, and steroid-resistant nephrotic syndrome secondary to biopsy proven FSGS leading to ESRF. Concerning ESRF, kidney transplantation is the therapy of choice since FSGS does not recur in the graft. However, with respect to the underlying immune disorder and the increased susceptibility to life threatening infections, the question of the optimal immunosuppressive therapy after renal transplantation remains unresolved. Under conventional immunosuppressive regimens some SIOD patients have developed severe disseminated cutaneous papilloma virus infections or EBV associated lymphoproliferative disease. We present several cases of children with SIOD (four of five had SMARCAL1 mutations) and monotherapy maintenance immunosuppression after renal transplantation and compare them with 13 patients from the SIOD registry. We have found that post-renal transplantation immunosuppressive monotherapy results in a good outcome with a reduced number of severe infections. Due to the underlying immunodeficiency in SIOD, limited immunosuppression may be possible without increasing the risk of acute or chronic rejection.

Serum T-Lymphocyte Cytokines Cannot Predict Early Acute Rejection in Renal Transplantation

Despite numerous studies, the precise role of Th1/Th2 cytokines in acute renal allograft rejection remains unclear. To provide insight into the role of cytokines in acute allograft rejection, we measured serum T-cell cytokine concentrations for correlation with clinical events after renal transplantation in adults. Serum Th1 (interleukin-2 [IL-2] and interferon-gamma [IFN gamma] and Th2 (IL-4, IL-10) cytokine concentrations were measured in 60 consecutive living donor kidney transplant recipients namely, 40 males, overall mean age 38.82 years), on the day before as well as 7 and 14 days posttransplantation using ELISA. Patients were stratified based upon acute rejection episode (ARE) in the first month after transplantation. Immunosuppression consisted of cyclosporine, mycophenolate mofetil, and prednisolone. ARE was diagnosed based on an increased plasma creatinine of more than 50%, sonographic analysis, radioisotope scan, pathologic findings, or measured cyclosporine blood levels. Twelve ARE were diagnosed among patients (20%). There was no significant difference between the 2 groups with respect to the mean serum concentration values of IL-2, IL-10, IL-4, and IFN gamma on the day before or 7 or 14 days after transplantation. This study showed that there was no correlation between the Th1/Th2 serum cytokine profiles and early ARE in living donor kidney transplantation.

Validation of Immunological Biomarkers for the Pharmacodynamic Monitoring of Immunosuppressive Drugs in Humans

Pharmacodynamic monitoring (PD) can evaluate the efficacy of immunosuppressive drug therapies. In this study, the expressions of PD biomarkers [lymphocyte proliferation, CD25 and CD71 expression, interleukin-2 (IL-2), and tumor necrosis factor-alpha (TNF-alpha) synthesis] were determined in whole-blood assays and were validated for their application in PD of immune modulators in future clinical trials. Initially, the assay conditions were re-evaluated. The measurement of T-lymphocyte proliferation and activation marker expression in whole-blood cultures resulted in optimized stimulation for 72 hours with 7.5 microg/mL concavalin A. Intracellular cytokine expression of CD3+ T-cells received optimized stimulation for 4 hours with 15 ng/mL phorbol 12-myristate 13-acetate and 0.75 microg/mL ionomycin. Statistical assay parameters (intra-assay, intra-individual, and interindividual variabilities) were determined. It was found that blood storage for up to 24 hours is possible without any change in biomarker expression. Dosage effects of immunosuppressive drugs (tacrolimus, cyclosporin A, sirolimus, mycophenolic acid, and methylprednisolone) were evaluated in vitro and the assay was applied successfully to dialysis, renal transplant, and liver transplant patients. We conclude that these biomarkers used in whole-blood assays are suitable for PD of immune modulators in clinical trials.

Impaired erythropoietin production in liver transplant recipients: the role of calcineurin inhibitors

Anemia is common following liver transplantation. Because cyclosporine inhibits erythropoietin (Epo) production in experimental models, we investigated whether Epo production was impaired in liver transplant recipients receiving a cyclosporine- or tacrolimus-based immunosuppressive regimen. First, serum Epo levels were measured before and 1 year after transplantation in 35 liver transplant recipients. Second, serum Epo levels were compared in a large series of liver transplant recipients with stable graft and renal functions: 27 receiving a cyclosporine-based and 31 receiving a tacrolimus-based immunosuppressive regimen. A reference group was made up of 22 blood donors and 21 nontransplanted subjects with iron-deficiency anemia. Serum Epo levels were significantly lower after than before liver transplantation, especially in cyclosporine-treated patients. Serum Epo concentrations correlated with hematocrit values in both transplant recipients and control subjects. Using multiple linear regression models, the polynomial relationship between hematocrit and serum Epo values was similar to the control group in patients under tacrolimus, whereas Epo production was significantly reduced in patients under cyclosporine-based immunosuppression. Hematocrit values and the type of calcineurin inhibitor were the only parameters independently related to Epo levels. In conclusion, cyclosporine, but not tacrolimus, inhibits Epo production at the doses used in clinical practice.

TH1/TH2 cytokine analysis in Iranian renal transplant recipients

The pretransplant cytokine profile of donor and recipient blood and tissues may be associated with transplant outcome. A Th1 response is generally associated with transplant rejection, while a Th2 response may lead to tolerance and stable graft survival. A total of 56 (37 male and 19 female) patients of mean 36 +/- 5 years were candidates for living unrelated kidney transplantation. Serum samples were collected 24 hours pretransplantation as well as at 1 and 2 weeks posttransplantation. Immunosuppression consisted of cyclosporine, prednisolone, and mycophenolate mofetil. Among the transplanted patients, 19 (33.9%) individuals experienced an acute rejection episode, as proven by biopsy, as well as an increased serum creatinine and blood urea nitrogen, within 14 days after transplantation. We determined serum concentrations of interleukin (IL) 2 and interferon (IFN)-gamma for Th1 and IL4 and IL10 for Th2 by an enzyme-linked immunosorbent assay method (Bender med system kits, Germany). Among Th1 cytokines, the mean concentration levels for groups with versus without acute rejection were: IL-2 pretransplant 15 pg/mL vs 6.8 pg/mL, respectively (P = .005); IL-2 at 1 week, 19 pg/mL vs 4.85 pg/mL, respectively (P = .001); IL-2 at 2 weeks, 21.1 pg/mL vs 4.65 pg/mL, respectively (P = .0001); IFN-gamma pretransplant 161.1 pg/mL vs 65.2 pg/mL, respectively (P = .001); IFN-gamma at 1 week, 175.6 pg/mL vs 66.5 pg/mL, respectively (P = .001); and IFN-gamma at 2 weeks, 173.7 pg/mL vs 77.1 pg/mL (P = .001). IL-2 and IFN-gamma levels were significantly higher in the group with acute rejection versus those without acute rejection. In conclusion, these data suggest that cytokine analysis, especially of Th1 cytokines, might be a valuable prognotic index of kidney transplant outcome.

Value of Pretransplantation Cytokine Profiles for Predicting Acute Rejection in Renal Transplant Recipients

Episodes of acute rejection may represent an important risk factor for the development of chronic allograft nephropathy. Various studies have shown that pretransplant cytokine profiles in recipient blood are associated with transplant outcome. Serum samples were collected 24 hours before transplantation from 57 patients (38 men and 19 women of age 36 +/- 5 years) receiving kidneys from unrelated living donors. Additional samples were collected at 1 and 2 weeks after transplantation, as well as during every rejection episode. The immunosuppression consisted of a cyclosporine, prednisolone, and mycophenolate mofetil. Among the transplanted patients, 19 (33.3%) individuals experienced an acute rejection episode based on an increased level of serum creatinine and blood urea nitrogen during the first 14 days after transplantation. TGF-beta, IL-2 and IFN-gamma serum levels were determined by an ELISA method using Bindermed system kits. The mean concentration of TGF-beta before transplantation tended to be lower among patients with acute rejection episodes compared to those with stable graft (75,265 versus 85,394 pg/mL; P = .34) and at 1 week after transplantation (77,558 versus 84,390 pg/mL), although the differences were not significant. Among patients with rejection the mean IL-2 concentration was significantly higher before, at 1 week, and at 2 weeks after transplantation (15.0 versus 6.8 pg/mL, P = .005; 19.0 versus 4.9 pg/mL, P = .001; and 21.1 versus 4.7 pg/mL, P = .0001). The mean concentration of IFN-gamma was significantly higher pre- and at 1 and 2 weeks posttransplantation in patients with acute rejection episodes (161.1 versus 65.2, 175.6 versus 66.5 and 173.7 versus 77.1 pg/mL, all P < .001). In conclusion, evaluation of Th1 cytokines before transplantation may represent valuable predictive marker for an acute rejection episode.

Pharmacodynamics in the development of new immunosuppressive drugs

Over the past 10-20 years a number of immunosuppressive drugs, such as cyclosporine A, tacrolimus, sirolimus, or mycophenolate mofetil have been approved for clinical use and have been highly successful in preventing or delaying graft rejection. Nevertheless, there is an incessant need for better and safer drugs to improve short-term and long-term outcomes following transplantation. A number of low-molecular-weight molecules that interfere with immune cell functions are in development. These include molecules that inhibit the janus protein tyrosine kinase JAK3, compounds that alter lymphocyte trafficking (the sphingosine-1-phosphate receptor antagonist FTY720), and new malononitrilamides (FK778). All seem to show promising therapeutic potential. Among the biologic agents, there are high expectations for antibodies or recombinant chimeric molecules targeting costimulatory surface molecules or pathways involved in the migration of immune cells. The list of such targets includes the ligand pairs CD28:B7, CD154:CD40, LFA-1:ICAM-1, ICOS:B7RP-1, and VLA-4:VCAM-1. However, the clinical development of drugs for transplantation has proved to be difficult, complex, and time consuming. Therefore, newly emerging drug candidates will also demand better methods for monitoring their efficacy as well as their side effects in vivo. Pharmacokinetics (PK) and pharmacodynamics (PD) are complementary approaches used to select drugs on the basis of their in vivo efficacy as well as safety. Whereas PK monitors the handling of the drug by the body, PD focuses on the biologic effect of the drug on its target. Therefore, PD studies of in vivo efficacy are useful for clinical decisions to determine the optimal dose and type of immunosuppressant. At the preclinical stage, PD is aimed at accelerating the selection of lead compounds via PD-controlled trials in animals. Moreover, PD can help to discover new mechanisms of action for a drug or a drug candidate. However, its full potential has not been used, mainly because of laborious and time-consuming methodology. This review focuses on established and novel PD/PK approaches to assess immunosuppressive compounds in the context of new evolving drugs or drug combinations.

Calcineurin Inhibitors: A Novel Approach to Canine Atopic Dermatitis

The introduction of calcineurin inhibitors represents a major addition to the armamentarium of drugs available to veterinary clinicians for the management of allergic skin diseases. Both cyclosporine and tacrolimus have been proven to be well tolerated and effective for the treatment of atopic dermatitis in dogs. Although broad spectrum in their mechanism of action, they lack the major adverse effects of glucocorticoids and provide an appealing alternative to traditional therapies. The purposes of this article are to review clinically relevant information regarding these agents and to provide tips for maximizing the benefit obtained from these therapies.

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

Defective inhibition of peripheral CD8+ T cell IL-2 production by anti-calcineurin drugs during acute liver allograft rejection

BACKGROUND

The aim of this study was to evaluate calcineurin activity and interleukin-2 (IL-2) expression by peripheral blood cells as a means of assessing the immune status of liver transplant recipients.

METHODS

Twenty-one patients were studied in a randomized study comparing cyclosporine and tacrolimus as the main immunosuppressive drug. Calcineurin activity was determined after separation of phosphorylated and dephosphorylated products of a calcineurin specific peptide substrate by high performance liquid chromatography(HPLC). Intracellular IL-2 expression was measured by flow cytometry. In 34 additional patients, intracellular IL-2 expression was prospectively measured.

RESULTS

Calcineurin activity fell after transplantation. Values were marginally higher in patients with acute rejection (P=0.059). The percentage of IL-2-producing T cells fell after transplantation. This percentage did not differ between patients with and without rejection. In contrast, the proportion of IL-2-producing CD8+ T cells was higher in patients with acute rejection than in patients free of acute rejection (P=0.003). Moreover, pretransplantation IL-2 expression by CD8+ T cells was higher in patients who subsequently developed acute rejection, suggesting that IL-2 production may be constitutively higher in those patients. The results obtained in the 34 additional patients confirmed these results.

CONCLUSIONS

These data suggest that quantification of intracellular IL-2 in CD8+ T cells may be a useful index of immune status in liver transplant recipients. Preoperative IL-2 levels might serve to individually tailor the immunosuppressive regimen.

Cyclosporine: advantages versus disadvantages vis-à-vis tacrolimus

Despite a different molecular structure and biochemical properties, cyclosporine and tacrolimus--by inhibiting calcineurin activity--have been shown in the previous two decades of solid organ transplantation to be well tolerated and effective immunosuppressants. Initial randomized clinical trials showed a lower incidence of acute rejection in tacrolimus than in cyclosporine-treated patients, in combination with steroids and azathioprine. But in conjunction with mycophenolate mofetil, the difference in the incidence of acute rejection episodes is less clear. In general, short- and medium-term outcome variables (1-year serum creatinine, graft and patient survival) with cyclosporine and tacrolimus are excellent, and (almost) identical, with both substances having the same intrinsic nephrotoxic potential. On the other hand, cyclosporine and tacrolimus have a different impact on cardiovascular risk factors with tacrolimus having a better profile on arterial tension and lipid metabolism and cyclosporine on glucose metabolism. However, at present no data are available to discern that these differences in risk profile alter patient or graft survival or long-term cardiovascular morbidity/mortality. Therefore, prospective long-term trials are needed to study the quantitative impact of different immunosuppressive agents and concomitant cardiovascular risk factors on long-term patient and graft survival, before evidence-based (patient, graft, or cardiovascular) risk reduction can be firmly claimed by tailoring calcineurin inhibitors.

The Severity of Infection Induces a Shift in the Type 1/Type 2 T-Helper Cell Balance in Patients with or without Peritonitis

BACKGROUND

A type-1 to type-2 T-helper cell (Th1/Th2) shift is hypothesized to occur among patients with severe trauma and pancreatitis. It was hypothesized that the Th2 situation caused an immune-suppressed period that led to a critical imbalance in the patients' conditions, with an increased risk of multiple organ failure and mortality.

METHODS

In eight patients with localized intra-abdominal infection (diverticulitis) and six patients with peritonitis due to perforation of a hollow viscus, we examined the cytokine response of CD3(+) T cells in the greater omentum and in the peripheral blood by in vitro stimulation, intracellular cytokine staining, and flow cytometry for TNF-alpha, IFN-gamma, IL-2, and IL-4. Follow-up cytokine assays were carried out on peripheral blood on days 3 and 7. Different levels of cytokine expression in each group were examined to determine the origin of the lymphocytes, both from omentum or peripheral blood. Cytokine production in the diverticulitis group was compared with that of the peritonitis patients.

RESULTS

In localized infections (diverticulitis), there was higher expression of TNF-alpha (51%/35% positive cells in omentum/blood), IFN-gamma (47%/32%), and IL-2 (33%/20%) in the omentum than in the peripheral blood mononuclear cells (PMBCs), but this was not true for IL-4 expression (0.8%/1.3%). In patients with peritonitis, there were no differences in cytokine expression between lymphocytes from the greater omentum and from PMBCs for TNF-alpha (18%/21% omentum/blood), IFN-gamma (20%/22%), IL-2 (16%/12%), or IL-4 (10.9%/7.6%). Compared to the diverticulitis group, patients with peritonitis showed reduced expression for TNF-alpha, IFN-gamma, and IL-2, but there was a significantly higher response for IL-4 for both compartments.

CONCLUSIONS

There was a shift from Th1 to Th2 in patients with severe clinical symptoms of peritonitis. Immune suppression is evident because of the T cell response in the greater omentum, but immunosuppression seems to not reach its maximum level before day 7 post operation. This differs from findings in multiple trauma and pancreatitis; however, it is parallel to the clinical situation in patients with peritonitis.

Inflammatory bowel disease after liver transplantation: the effect of different immunosuppressive regimens

BACKGROUND

Seemingly conflicting results have been reported on the prevalence and severity of inflammatory bowel disease after liver transplantation. Regimens with different combinations of drugs can be used for immunosuppression after transplantation.

AIM

To study retrospectively the prevalence of inflammatory bowel disease after liver transplantation, and the possible relationship with maintenance immunosuppressive regimens.

METHODS

All 78 patients with end-stage primary sclerosing cholangitis (48 patients) or autoimmune cirrhosis (30 patients), transplanted between 1979 and July 2001, and with a follow-up of at least 1 year, were eligible for this study. In addition to patient and transplant characteristics, data on inflammatory bowel disease and immunosuppression before and after transplantation were collected. The Kaplan-Meier method was used for survival analysis. Possible risk factors for inflammatory bowel disease after transplantation were analysed by Cox univariate and multivariate regression.

RESULTS

The median follow-up after transplantation was 7.2 years (range, 1.1-22.3 years). Nine of 25 patients with pre-transplant inflammatory bowel disease experienced flare-ups after transplantation. Six of 53 patients without pre-transplant inflammatory bowel disease developed de novo inflammatory bowel disease after transplantation. The cumulative risks (standard errors in parentheses) for inflammatory bowel disease were 6% (3%), 12% (4%) and 20% (5%) at 1, 3 and 5 years after transplantation, respectively. The inflammatory bowel disease-free survival was significantly higher in patients not receiving tacrolimus vs. those receiving tacrolimus, in patients receiving azathioprine vs. those not receiving azathioprine and in patients taking the regimen prednisolone-azathioprine-ciclosporin A vs. those taking tacrolimus-prednisolone. Pre-transplant inflammatory bowel disease and the use of tacrolimus were found to be independent predictors for inflammatory bowel disease after transplantation.

CONCLUSIONS

The prevalence of inflammatory bowel disease after liver transplantation is affected by the immunosuppression used. Azathioprine seems to have a protective effect and tacrolimus a promoting effect.

Functional quantification of cyclosporine A and FK506 in human whole blood by flow cytometry, using the green fluorescent protein as an interleukin-2 reporter gene

The concentration of the immunosuppressive drugs cyclosporine A (CSA) and FK506 in biological fluids is routinely determined by antibody-based assays, which for several reasons do not give accurate information on the actual level of immunosuppression in the patient. To alleviate this problem, we developed a functional reporter gene assay which uses the enhancer fragment of the interleukin-2 promoter region driving the expression of the green fluorescent protein (GFP). This construct was stably transfected in the Jurkat human T lymphoblastoid cell line. Upon stimulation of the cell recipient, the GFP was produced and evaluated by flow cytometry. Immunosuppressants acting via inhibition of interleukin-2 synthesis, such as CSA or FK506, inhibited the production of GFP in a dose-dependent manner. This assay can be performed within a working day with a good reproducibility and was more sensitive than the antibody-based assays, since its detection limit was as low as 10 ng/ml for CSA and 0.5 ng/ml for FK506. We used it for the follow up of drug level present in the blood of transplanted patients, and compared the results with those obtained with the antibody-based assay routinely carried out in our hospital. The conclusions suggest that this assay is a valuable alternative to the presently available assays for the measurement of the immunosuppressive activity found in body fluids.

The ACVD task force on canine atopic dermatitis (XXII): nonsteroidal anti-inflammatory pharmacotherapy

The pharmacotherapy of canine atopic dermatitis has relied primarily on the use of glucocorticoids and anti-histamines. During the last decade, other anti-inflammatory drugs have been investigated in clinical trials. This paper will review the studies using misoprostol, cyclosporine, tacrolimus, phosphodiesterase inhibitors, capsaicin, leukotriene inhibitors and serotonin-reuptake inhibitors for treatment of dogs with atopic dermatitis. For each drug the mechanism of action, the rationale for use in atopic dermatitis, the clinical efficacy, reported adverse effects and strength of recommendation for treatment of canine atopic dermatitis are described. At the time of this writing, there is fair evidence to support the recommendation for using cyclosporine, misoprostol and pentoxifylline for treatment of canine atopic dermatitis. This recommendation can be strengthened by the performance of additional blinded randomized controlled trials with larger number of dogs. In contrast, there is insufficient evidence to recommend for or against treatment with tacrolimus, leukotriene inhibitors, serotonin-reuptake antagonists and capsaicin.

Lack of effect of chronic hepatitis C virus infection on T-cell cytokine production in chronic hemodialysis patients

It has been shown that chronic hemodialysis modifies, to some extent, the normal immune response by both T and B lymphocytes elicited by antigenic stimulation, e.g. by impairing the T-cell-dependent response after vaccination. A new technique, i.e. flow cytometry, enables to assess intracytoplasmically, at the single cell level, the production of a given cytokine. By using it, we studied in healthy volunteers (HV) and in chronic hemodialysis (CHD) patients, with respect to their hepatitis C virus (HCV) status, the production by the T lymphocytes of type 1, and type 2 cytokines. We studied the following cytokines (CK): IL-2, IL-4, IL-5, IL-6, IL-10, IFN-gamma and TNF-alpha in the T-cell lymphocytes (whole, CD4+ and CD8+). There were 13 HV and 59 CHD patients (36 HCV(-) and 23 HCV(+)). Amongst the latter, there were 32 men and 27 women, aged 59.5 +/- 2 years, undergoing CHD since 70 +/- 9.4 months. We found that: (1) the total number of lymphocytes as well as those expressing CD3, CD4, or CD19 were significantly decreased in CHD patients as compared to those from HV; (2) the total number of lymphocytes as well as their different subsets were similar in HCV(+) and in HCV(-) CHD patients; (3) the frequency of T-cell-expressing IL-5 or IL-10 was always low (<1%) in both HV and CHD groups; (4) overall in CHD patients, the mean percentages of T lymphocytes expressing IL-2, IL-4, IFN-gamma or TNF-alpha were respectively 31 +/- 13, 2.5 +/- 1.3, 28 +/- 12 and 34 +/- 11% and were not statistically different between HCV(+) and HCV(-) patients; (5) IL-2 was mainly produced by CD4+ T cells, whereas IFN-gamma was produced by CD8+ T cells, in both HV and CHD groups, and (6) the lymphocytes of CHD patients produced significantly more IL-2 and IL-4 than those from HV, suggesting an activation of their T lymphocytes. We conclude that using the cytokine flow cytometry assay, our study demonstrated that in HCV(+) CHD patients, as opposed to what has been described for HCV(+) patients with normal renal function, there was no impairment in the production of type 1 cytokines by peripheral blood mononuclear cells when compared to HCV(-) CHD patients. Conversely to HV, T lymphocytes from CHD patients are activated.

Pharmacodynamics of immunosuppressive drugs

The inability to measure the effects of immunosuppressive drugs on immune cells in vivo has always severely limited preclinical drug development, the design and interpretation of clinical trials and the optimal clinical use of this drug class in transplantation. Now, new technologies using microliter samples of whole blood and exploiting the specificity, sensitivity and versatility of flow cytometry have been developed. These novel techniques not only are illuminating the 'black box' that has obscured the pharmacodynamic effects of immunosuppressants but also are uncovering new mechanisms of action of these drugs. Pharmacodynamic assays measure biologically relevant events in vivo, since changes in lymphocyte functions in blood collected from immunosuppressed graft recipients faithfully reflect histopathologic events within allograft tissue.