Establishing pediatric immune response zones using the Cylex® ImmuKnowTM assay

Immune cell function assay and T lymphocyte counts lack association with rejection or infection in pediatric heart transplant recipients

INTRODUCTION

Immune cell function assay (ICFA) and CD3 lymphocyte counts have been considered to be useful in discerning the overall intensity of immunosuppression in pediatric orthotopic heart transplant (OHT) recipients.

METHODS

The aim of this retrospective analysis was to evaluate trends of ICFA and CD3 lymphocyte counts and their association with adverse outcomes post-OHT.

RESULTS

A total of 381 ICFA and 493 CD3 laboratory values obtained in 78 patients within six months post-OHT were analyzed. There were 14 patients treated for biopsy-proven acute rejection, four of whom had ISHLT grade 2R/3A rejection. In patients with rejection versus those without, CD3 and ICFA values were 122 (IQR 74.5-308) cells/mm² and 224.5 (IQR 132-343.5) ng/ml compared to 231.8 (IQR 68-421) cells/m² and 191 (IQR 81.5-333) ng/mL (p = NS for both). Twenty-six patients had at least one detectable cytomegalovirus or Epstein-Barr virus DNAemia within the study timeframe. In patients with viremia versus those without, CD3 and ICFA values were 278.5 (IQR 68-552) cells/mm² and 130 (IQR 48-284) ng/ml compared to 195 (IQR 74.5-402.5) cells/mm² and 212 (IQR 89-342) ng/ml (p = NS for both).

CONCLUSIONS

No association was found between these immune markers and adverse outcomes. In the absence of larger pediatric studies justifying the role of these tests in identifying elevated risk profiles post OHT, we do not recommend their routine use.

GRWR Correlates with the Metabolism of Tacrolimus after Pediatric Living Donor Liver Transplantation According to Donor CYP3A5 Polymorphism

Objectives. Tacrolimus is characterized by high pharmacokinetic variability in combination with a narrow therapeutic range. However, influence of donor CYP3A5 genotype and graft-to-recipient body weight ratio (GRWR) on tacrolimus’ pharmacokinetics after pediatric living donor liver transplantation (LDLT) remains unclear. Methods. A total of 174 LDLT recipients (<6 y) were grouped according to donor CYP3A5 genotypes (nonexpressor (NEX) or expressor (EX)) and GRWR (<3.0% (SS, small-size) or ≥3.0% (LS, large-size)): SS/NEX ( $n=40$ ), SS/EX ( $n=38$ ), LS/NEX ( $n=48$ ), and LS/EX ( $n=48$ ). Pharmacokinetics of tacrolimus and clinical outcomes were analyzed. Results. The relationships between the concentration-dose ratio and donor CYP3A5 genotypes and graft size were examined 3, 7, 14, and 30 days after the transplantation. Tacrolimus C0 levels varied greatly among groups, although recipients started with the same initial dosage. LS/EX recipients had significantly lower C0 levels in comparison with those of other groups. The use of CYP3A5-EX-grafts and a greater GRWR both resulted in significantly higher TAC dose requirements and lower C/D ratios. However, the significance of GRWR no longer exists 3 months after transplantation. The multivariate generalized linear mixed model analysis showed that donor CYP3A5 genotypes ( $F=11.876$ ; $P=0.01$ ) and GRWR ( $F=4.631$ ; $P=0.033$ ) were independent impact factors for C/D ratios 3, 7, 14, and 30 days after transplantation. Donor CYP3A5-EX genotype was associated with significantly increasing risks of infectious complications and significantly lower Cylex ATP values. However, no significant difference was observed in acute rejections among 4 groups. Conclusions. Monitoring of C0 levels alone is not reliable to guide tacrolimus administration. Donor CYP3A5 and GRWR both significantly affect tacrolimus pharmacokinetics after pediatric LDLT. The use of Cylex ATP tests would be helpful to avoid overimmunosuppression.

Treatment optimization of maintenance immunosuppressive agents in pediatric renal transplant recipients

Introduction: Graft survival in pediatric kidney transplant patients has increased significantly within the last three decades, correlating with the discovery and utilization of new immunosuppressants as well as improvements in patient care. Despite these developments in graft survival for patients, there is still improvement needed, particularly in long-term care in pediatric patients receiving grafts from deceased donor patients. Maintenance immunosuppressive therapies have narrow therapeutic indices and are associated with high inter-individual and intra-individual variability.Areas covered: In this review, we examine the impact of pharmacokinetic variability on renal transplantation and its association with age, genetic polymorphisms, drug-drug interactions, drug-disease interactions, renal insufficiency, route of administration, and branded versus generic drug formulation. Pharmacodynamics are outlined in terms of the mechanism of action for each immunosuppressant, potential adverse effects, and the utility of pharmacodynamic biomarkers.Expert opinion: Acquiring abetter quantitative understanding of immunosuppressant pharmacokinetics and pharmacodynamic components should help clinicians implement treatment regimens to maintain the balance between therapeutic efficacy and drug-related toxicity.

Immune cell function assays in the diagnosis of infection in pediatric liver transplantation: an open-labeled, two center prospective cohort study

BACKGROUND

Limited studies have been performed in assessment of immune status of pediatric liver transplants (PLTs). We conducted this study to evaluate Cylex immune cell function assay in diagnosis of infection and its potential clinical application in Chinese infant PLTs.

METHODS

In this prospective cohort study, 227 infant PLTs from two medical centers were enrolled, and 216 completed the study. Cylex ATP values were measured before and after liver transplantation (LT) at week 1, 2, 3, 4, 8, 12 and 24 respectively. Accordingly, patients' clinical records, including demographic data, liver function results, tacrolimus dosages and concentrations were collected and analyzed.

RESULTS

One hundred and sixty of 216 PLTs (74.1%) were diagnosed infection based on the parameters including abnormal vital signs, imaging changes, and pathogens detection, while 44 (20.4%) were clinically stable and 12 (5.6%) experienced acute rejection. The median Cylex ATP value in infant PLTs post-surgery reduced significantly in infection group compared to stable group (median, 137 vs. 269 ng/mL, P<0.001). Receiver operating characteristic (ROC) curve analysis determined that the cut-off value of Cylex ATP was 152 ng/mL in diagnosis of infection [area under the curve (AUC): 0.784, 95% CI: 0.720-0.848]. Meanwhile, Cylex ATP value showed no correlation to tacrolimus dosage, blood concentration, dose-normalized concentration/dose ratio or Kaup index. However, it tended to correlate weakly with the white blood cell (WBC) number (R =0.462, P<0.0001) and lymphocyte counts (R =0.363, P<0.0001).

CONCLUSIONS

In this study, we demonstrated that low Cylex ATP represented partly over-immunosuppression and had diagnostic value in infant PLTs with infections, which might assist individualized immunosuppression in PLT patients.

T-cell exhaustion correlates with improved outcomes in kidney transplant recipients

Continuous antigen stimulation during chronic infection or malignancy can promote functional T cell silencing, a phenomenon called T cell exhaustion. The prevalence and impact of T cell exhaustion following organ transplantation, another immune stimulus with persistently high antigen load, are unknown. Here, we characterized serially collected peripheral blood mononuclear cells from 26 kidney transplant recipients using time-of-flight mass cytometry (CyTOF) to define distinct subsets of circulating exhausted T cells and their relationship to induction therapy and allograft function. We observed an increase in specific subsets of CD4⁺ and CD8⁺ exhausted T cells from pre-transplant to 6-months post-transplant, with greater increases in participants given anti-thymocyte globulin induction than in participants who received no induction or non-depleting induction. The percentages of exhausted T cells at 6 months correlated inversely with adenosine triphosphate (ATP) production (a surrogate of T cell function) and with allograft interstitial fibrosis. Guided by the CyTOF data, we delineated a PD-1⁺CD57^- phenotype for CD4⁺ and CD8⁺ exhausted T cells, and confirmed that these cells have limited capacity for cytokine secretion and ATP production. In an independent cohort of 50 kidney transplant recipients, we confirmed the predicted increase of PD-1⁺CD57^- exhausted T cells after lymphocyte-depleting induction therapy and its direct correlation with better allograft function. Our findings suggest that monitoring T cell exhaustion can be useful for post-transplant risk assessment and support the need to develop and test strategies aimed at augmenting T cell exhaustion following kidney transplantation.

Delayed introduction of immunosuppressive regimens in critically ill patients after liver transplantation

BACKGROUND

The manipulation of immunosuppression therapy remains challenging in patients who develop infectious diseases or multiple organ dysfunction after liver transplantation. We evaluated the outcomes of delayed introduction of immunosuppression in the patients after liver transplantation under immune monitoring with ImmuKnow assay.

METHODS

From March 2009 to February 2014, 225 consecutive liver recipients in our institute were included. The delayed administration of immunosuppressive regimens was attempted in 11 liver recipients with multiple severe comorbidities.

RESULTS

The median duration of non-immunosuppression was 12 days (range 5-58). Due to the infectious complications, the serial ImmuKnow assay showed a significantly low ATP level of 64±35 ng/mL in the early period after transplantation. With the development of comorbidities, the ImmuKnow value significantly increased. However, the acute allograft rejection developed when a continuous distinct elevation of both ATP and glutamyltranspeptidase levels was detected. The average ATP level measured just before the development of acute rejection was 271±115 ng/mL.

CONCLUSIONS

The delayed introduction of immunosuppressive regimens is safe and effective in management of critically ill patients after liver transplantation. The serial ImmuKnow assay could provide a reliable depiction of the dynamics of functional immunity throughout the clinical course of a given patient.

Correlation Between Survival Interval and CD4+ T-Cell Intracellular ATP Levels in Liver Transplant Recipients

OBJECTIVE

The objectives of this study were to analyze the potential correlation between post-liver transplantation survival interval and CD4⁺ T-cell intracellular ATP (iATP) levels, and to describe the distribution of CD4⁺ T-cell iATP levels in liver transplant recipients.

METHODS

This was a retrospective analysis of clinical data of 273 patients who underwent liver transplantation from July 2010 to October 2012 in our center and achieved long-term stable survival. CD4⁺ T-cell iATP level was detected using Cylex ImmuKnow assay. Post-liver transplantation survival was analyzed.

RESULTS

CD4⁺ T-cell iATP level significantly differed among patients with different post-liver transplantation survival intervals. The peak CD4⁺ T-cell iATP levels typically occurred within the first 3 postoperative months.

CONCLUSIONS

Post-liver transplantation survival interval is correlated with CD4⁺ T-cell iATP levels.

Altered Intracellular ATP Production by Activated CD4+ T-Cells in Very Preterm Infants

Background. The neonatal immune system is not fully developed at birth; newborns have adequate lymphocytes counts but these cells lack function. Objective. To assess the activity of T-cells and the influence of the main perinatal factors in very preterm infants (birth weight < 1500 g). Design. Blood samples from 59 preterm infants (21/59 were dizygotic twins) were collected at birth and at 30 days of life to measure CD4+ T-cell activity using the ImmuKnow™ assay. Fifteen healthy adults were included as a control group. Results. CD4+ T-cell activity was lower in VLBW infants compared with adults (p < 0.001). Twins showed lower immune activity compared to singletons (p = 0.005). Infants born vaginally showed higher CD4+ T-cell activity compared to those born by C-section (p = 0.031); infants born after prolonged Premature Rupture of Membranes (pPROM) showed higher CD4+ T-cell activity at birth (p = 0.002) compared to infants born without pPROM. Low CD4+ T-cell activity at birth is associated with necrotizing enterocolitis (NEC) in the first week of life (p = 0.049). Conclusions. Preterm infants show a lack in CD4+ T-cell activity at birth. Perinatal factors such as intrauterine inflammation, mode of delivery, and zygosity can influence the adaptive immune activation capacity at birth and can contribute to exposing these infants to serious complications such as NEC.

Immune function monitoring in lung transplantation using adenosine triphosphate production: time trends and relationship to postoperative infection

PURPOSE

The ImmuKnow (IK) assay is a comprehensive immune function test that involves measuring adenosine triphosphate produced by the cluster of differentiation 4+ T lymphocytes in peripheral blood. The aim of this study was to analyze the time trends of IK values and assess the relationship between IK values and infections in lung transplants.

METHODS

We prospectively collected 178 blood samples from 22 deceased-donor lung transplant (DDLT) recipients and 17 living-donor lobar lung transplant (LDLLT) recipients. A surveillance IK assay was performed postoperatively, then after 1 week and 1, 3, 6, and 12 months.

RESULTS

Time trends of IK values in stable recipients peaked 1 week after DDLT (477 ± 247 ATP ng/ml), and 1 month after LDLLT (433 ± 134 ng/ml), followed by a gradual decline over 1 year. The mean IK values in infections were significantly lower than those in the stable state (119 vs 312 ATP ng/ml, p = 0.0002).

CONCLUSIONS

IK values increased sharply after lung transplantation and then decreased gradually over time in the first year, suggesting a natural history of immune function. IK values were also significantly reduced during infections. These results may provide new insights into the utility of immune monitoring after lung transplantation.

Green Tea Catechin Metabolites Exert Immunoregulatory Effects on CD4(+) T Cell and Natural Killer Cell Activities

Tea catechins, such as (-)-epigallocatechin-3-O-gallate (EGCG), have been shown to effectively enhance immune activity and prevent cancer, although the underlying mechanism is unclear. Green tea catechins are instead converted to catechin metabolites in the intestine. Here, we show that these green tea catechin metabolites enhance CD4(+) T cell activity as well as natural killer (NK) cell activity. Our data suggest that the absence of a 4'-hydroxyl on this phenyl group (B ring) is important for the effect on immune activity. In particular, 5-(3',5'-dihydroxyphenyl)-γ-valerolactone (EGC-M5), a major metabolite of EGCG, not only increased the activity of CD4(+) T cells but also enhanced the cytotoxic activity of NK cells in vivo. These data suggest that EGC-M5 might show immunostimulatory activity.

Evaluation of the immune function assay in pediatric living donor liver transplantation

The immune function (ImmuKnow) assay is a measure of cell-mediated immunity based on the peripheral CD4+ T cell ATP activity. The efficacy of ImmuKnow in pediatric LDLT is not well documented. The aim of this study was to assess the correlations between the ImmuKnow and the clinical status in pediatric LDLT recipients. A total of 716 blood samples were obtained from 60 pediatric LDLT recipients (one month to 16 yr of age). The recipient's status was classified as follows: stable, infection, or rejection. The ImmuKnow values in the pediatric LDLT recipients with a clinically stable status had a lower immune response (IQR 85-297 ATP ng/mL) than that previously reported in adults. Meanwhile, the ImmuKnow values of the stable patients were not correlated with age. Furthermore, a significant difference was found in the ImmuKnow values between the bacterial or fungal infection and stable groups, but not between the CMV or EBV infection and stable groups. The ImmuKnow levels in the pediatric LDLT were lower than those observed in the adult LDLT. The proposed reference value is between 85 and 297 ATP ng/mL in pediatric LDLT recipients. We conclude that the ImmuKnow assay could be helpful for monitoring pediatric LDLT recipients with bacterial or fungal infections.

CD4+ T-lymphocytes are activated by surgical stress following colorectal resection in cancer patients

The aim of the present study was to measure adenosine triphosphate (ATP) levels in CD4⁺ T cells as a marker of T-cell activity following surgery for colorectal cancer using the ImmuKnow assay kit. A total of 16 consecutive patients who underwent surgical resection for colorectal cancer between August and December, 2012 were enrolled in this study, of whom 7 underwent laparoscopic resection and 9 underwent open abdominal surgery. The intracellular ATP levels in CD4⁺ T-lymphocytes were measured using the ImmuKnow assay kit preoperatively and on the 1st, 4th and 8th postoperative days, as were the white blood cell (WBC) count, lymphocyte count and C-reactive protein (CRP) levels. The ATP level of the CD4⁺ T-cells was significantly elevated on the 1st day following surgery compared to the preoperative level (P<0.01) and gradually returned to preoperative levels; the lymphocyte count was significantly decreased on the 1st postoperative day (P<0.001). In addition, the ImmuKnow assay demonstrated that only the ATP level, but not the WBC count, lymphocyte count or CRP level, exhibited a significant difference on the 1st (P=0.080) and 8th (P=0.042) postoperative days between the laparoscopic and open abdominal surgery groups. In conclusion, the ATP level of CD4⁺ T-lymphocytes was increased in response to surgical stress, in tandem with a decrease in the lymphocyte count. Therefore, the ImmuKnow assay kit may be clinically applicable for monitoring the immune response following surgery, as it exhibits a higher sensitivity compared to other assays.

Immune cell function assay in pediatric heart transplant recipients

The ImmuKnow ICFA reports ex vivo CD4 lymphocyte activation to quantify immunosuppression. Limited organ and age-specific data exist for pediatric heart transplant recipients. We sought to examine their normative values and ICFA's association with rejection/infection. A total of 380 ICFAs from 58 heart transplant recipients (6.5/recipient) were studied retrospectively. The median age at the time of their first ICFA was 5.3 yr (IQR 2.4-12.1 yr). ICFA levels during immunologic stability (n = 311) were a median of 305 (IQR: 172-483) and mean of 353 (s.d. ± 224) ng ATP/mL. ICFA levels trended lower with advancing age. ICFA levels during immunologic stability increased over time from transplant after the first six months but were not correlated with calcineurin inhibitor levels or the type used. There is no association between ICFA values during stability and rejection (median 368 ATP ng/mL; IQR 153-527) or infection (median 293 ATP ng/mL; IQR 198-432). In contrast to the manufacturer's suggested ranges, the immunologic stable ranges in pediatric cardiac recipients were very different. ICFA values during immunologic stability are related to time from transplant in pediatric heart recipients. ICFA's ability to discriminate rejection or infection from immunologic stability was not demonstrated.

Immune cell function assay does not identify biopsy-proven pediatric renal allograft rejection or infection

Management of pediatric renal transplant patients involves multifactorial monitoring modalities to ensure allograft survival and prevent opportunistic infection secondary to immunosuppression. An ICFA, which utilizes CD4 T-cell production of ATP to assess immune system status, has been used to monitor transplant recipients and predict susceptibility of patients to rejection or infection. However, the validity of this assay to reflect immune status remains unanswered. In a two-yr retrospective study that included 31 pediatric renal transplant recipients, 42 patient blood samples were analyzed for immune cell function levels, creatinine, WBC (white blood cell) count, immunosuppressive drug levels, and viremia, concurrent with renal biopsy. T-cell ATP production as assessed by ICFA levels did not correlate with allograft rejection or with the presence or absence of viremia. ICFA levels did not correlate with serum creatinine or immunosuppressive drug levels, but did correlate with WBC count. The ICFA is unreliable in its ability to reflect immune system status in pediatric renal transplantation. Further investigation is necessary to develop methods that will accurately predict susceptibility of pediatric renal transplant recipients to allograft rejection and infection.

Utility of an immune cell function assay to differentiate rejection from infectious enteritis in pediatric intestinal transplant recipients

The Cylex Immune Cell Function Assay measures cell-mediated immunity based on ATP production by stimulated CD4 + cells. We hypothesized that this test would discriminate acute cellular rejection (ACR) from infectious enteritis (IE) in pediatric intestinal transplant (ITx) recipients with allograft dysfunction. We retrospectively analyzed 224 Cylex assays drawn in 47 children who received 53 ITx. Samples were classified as stable, ACR, or IE based on clinical status. ATP values were analyzed using Kruskal-Wallis and t-tests. Overall, there was a statistically significant difference in ATP values based on clinical status (p = 0.03); however, overlap was observed between groups. The median ATP value during ACR was significantly greater than during stable periods (p = 0.02). No difference was seen in IE vs. stability (p = 0.8). The difference in median ATP value in ACR vs. IE approached significance (p = 0.1). Relative to previous levels, ACR episodes were associated with a median ATP increase of 101 ng/mL and IE episodes with a decrease of 3 ng/mL (p = 0.3). These data indicate that the Cylex assay has limited utility in differentiating ACR from IE, largely due to interpatient variability. Following longitudinal intrapatient trends may be an adjunctive tool in discriminating IE from ACR and guiding immunosuppression adjustments in select patients.

Issues in solid-organ transplantation in children: translational research from bench to bedside

In this review, we identify important challenges facing physicians responsible for renal and cardiac transplantation in children based on a review of the contemporary medical literature. Regarding pediatric renal transplantation, we discuss the challenge of antibody-mediated rejection, focusing on both acute and chronic antibody-mediated rejection. We review new diagnostic approaches to antibody-mediated rejection, such as panel-reactive antibodies, donor-specific cross-matching, antibody assays, risk assessment and diagnosis of antibody-mediated rejection, the pathology of antibody-mediated rejection, the issue of ABO incompatibility in renal transplantation, new therapies for antibody-mediated rejection, inhibiting of residual antibodies, the suppression or depletion of B-cells, genetic approaches to treating acute antibody-mediated rejection, and identifying future translational research directions in kidney transplantation in children. Regarding pediatric cardiac transplantation, we discuss the mechanisms of cardiac transplant rejection, including the role of endomyocardial biopsy in detecting graft rejection and the role of biomarkers in detecting cardiac graft rejection, including biomarkers of inflammation, cardiomyocyte injury, or stress. We review cardiac allograft vasculopathy. We also address the role of genetic analyses, including genome-wide association studies, gene expression profiling using entities such as AlloMap®, and adenosine triphosphate release as a measure of immune function using the Cylex® ImmuKnow™ cell function assay. Finally, we identify future translational research directions in heart transplantation in children.

Clinical value of a single determination of intracellular ATP levels in stimulated CD4+ T lymphocytes in pediatric patients with stable liver transplantation

In the follow-up of transplanted patients under immunosupression, the functional assessment of CD4+ T cells activation by measuring intracellular ATP levels in vitro, using the Immuknow test give information on how immune system is functioning. Therefore, it has been reported that low levels of ATP correlate with the risk of opportunistic infection. Although limited, comprehensive results in adult recipients as well as in pediatric transplanted patients have been reported. Forty stable liver pediatric transplanted patients (mean age: 11.0 years [SD 5.65]), within at least 1 year of transplant were selected for a scheduled review, and an unique determination of Immuknow was performed. Average ATP levels were 317 ng/mL (200-400 ng/mL) which were similar to the values observed in adult population. ATP values among patients with monotherapy Cyclosporin A (CSA) or tacrolimus (TAC) were significantly higher (P = .005) than in patients with double immunosupressive therapy using either CSA/TAC + Mycophenolate Mofetil (MMF). In CSA treatment, there are significant differences (P = .0003) between monotherapy and double therapy, but in the case of TAC we did not find differences (P > .1). A single determination of levels of ATP on CD4+ lymphocytes, can provide additional information that could be used as a complementary test to guide immunosuppressive therapy in paediatric liver transplant recipients.

Immune function assay (ImmuKnow) as a predictor of allograft rejection and infection in kidney transplantation

BACKGROUND

The Cylex ImmuKnow (IK) assay provides a rapid and quantitative assessment of T-cell-mediated immune function. Studies have shown correlations between ImmuKnow assay and adverse events, such as immunosuppression and low or high calcineurin inhibitor trough levels. We investigated the correlation between IK changes and rejection or infection in kidney transplant patients and studied the potential application of the IK assays in optimizing individual immunosuppressive therapy.

METHODS

ImmuKnow assay was used to determine dynamic intracellular ATP changes in CD4 cells in 193 samples from 42 kidney transplant patients and 25 healthy subjects. Patients were categorized into rejection, infection, and event-free groups. The IK values were assayed and analyzed between kidney transplant patients and healthy controls.

RESULTS

Most IK values fell between 200 and 599 ng/mL from pre-transplantation to 30 months post-transplantation. The mean IK values continuously increased throughout 30 months. Incidental allograft rejection patients had significantly higher IK values compared with the event-free patients and controls. However, infection patients had significantly lower IK values. Seven days after treatment, IK values in rejection/infection patients were different compared with the values in autograft patients, and there was a significant correlation between calcineurin inhibitor (FK506) trough levels and IK values in rejection/infection patients. Serum creatinine levels in the rejection patients were significantly higher than those in the event-free patients, and C-reactive protein levels were significantly higher in the infection patients compared with the event-free patients.

CONCLUSIONS

The IK assay combined with other biomarkers can be used to identify kidney transplant patients at high risk of rejection and infection.

Significant reduction of ATP production in PHA-activated CD4+ cells in 1-day-old blood from transplant patients

BACKGROUND

Global immunosuppression can be measured by assessing adenosine triphospate (ATP) levels in mitogen-stimulated CD4+ T cells.

METHODS

We investigated the effect of storage time on ATP levels in 234 blood samples from 18 healthy individuals and 152 transplant patients. The difference between day 0 (<13 hours post-blood draw) and day 1 (24-37 hours) measurements was analyzed and compared with various factors; a subset of samples was also analyzed in 6-hour intervals.

RESULTS

The ATP levels were significantly lower on day 1 compared with that on day 0 in healthy individuals (279±159 vs 414±159 ng/mL, P<0.001) and patients (356±209 vs 455±221 ng/mL, P<0.0001). Of the 18 healthy individuals, 17 showed ATP reduction, whereas 192 (89%) of 216 patients did so on day 1 (24.8±24.1%). In the time course analysis, ATP levels decreased with the blood storage time in healthy and patient samples, and the reduction began as early as 7 hours post-blood draw. The reduction rate was significantly higher in patient samples with low day 0 ATP levels compared with samples with moderate or high levels (44.7±31.3% vs 23.2±23.6% or 18.7±15.7%; P<0.001). The reduction rate in patients treated with alemtuzumab induction was slightly higher than that in daclizumab-treated patients (28.8±24.6% vs 21.3±21.3%, P=0.09). CD4+ cell number did not change within 24 hours post-blood draw, but CD4 expression decreased 2.0±2.8% (P<0.05).

CONCLUSIONS

The ATP levels are significantly lower in 1-day-old blood compared with fresh blood, suggesting that fresh blood should be used for assessing the T cell immune function to obtain the most accurate results.

Intracellular ATP production in CD4+ T cells as a predictor for infection and allograft rejection in trough-level guided pediatric liver transplant recipients under calcineurin-inhibitor therapy

BACKGROUND

The assessment of cell-mediated immune responses through the measurement of intracellular adenosine-tri-phosphate (iATP) production (Cylex ImmuKnow) as a pharmacodynamic biomarker of immune function represents a potential tool to optimize individual immunosuppressive therapy independent of drug dosage or trough levels. This study aims to investigate the correlations between iATP and adverse events, immunosuppression, calcineurin-inhibitor-trough levels, and age.

METHODS

In this prospective trial, 31 nontransplant pediatric subjects and 50 consecutive children were included after they underwent liver transplantation (LTX). During the study period, 4 allograft rejections and 3 acute infections occurred. The patients were treated with cyclosporine, tacrolimus, mycophenolate mofetil, and everolimus either as monotherapy or in combinations. The reactivity of the immune system was measured as iATP concentration in CD4+ T-cells after in vitro stimulation by phytohemagglutinin.

RESULTS

The iATP concentrations in patients with intercurrent, clinically significant infections were in the low immune response range (median iATP 181 versus 251 ng/mL, P = 0.308), whereas the patients with incidental allograft rejection had significantly higher iATP concentrations as compared with the event-free group (median iATP 444 versus 251 ng/mL, P = 0.017). However, there was a wide range of iATP concentrations in both nontransplant and LTX patient groups, and no clear iATP cut-off values for an increased risk of infection or rejection could be defined. Post LTX, stable-phase patients showed a significantly lower iATP compared with respective controls (median iATP 297 versus 384 ng/mL, P = 0.013). No significant correlation between calcineurin-inhibitor-trough concentrations and iATP was found. iATP was not correlated with age, but was inversely correlated with time after transplantation.

CONCLUSIONS

The observed correlation between clinical events and iATP concentrations is similar to the findings previously reported in adult patients who underwent transplantation. The lack of correlation of iATP with trough drug concentrations suggests that the ImmuKnow assay provides independent information that may be useful to guide immunosuppressive therapy in pediatric (liver) transplant patients. However, the wide range of iATP levels in event-free patients suggests that serial iATP measurements will be necessary to assess and guide the individual immunosuppressive therapy. Further investigations are needed to evaluate and extend these findings.

Lymphocyte ATP immune cell function assay in pediatric renal transplants: is it useful?

The ultimate goal for an allograft is a balanced immunosuppression to provide the longest graft survival with minimal side effects. In this retrospective study, we correlate the immunosuppresion level as determined using the Cylex assay (Immu know, Columbia, MD) with clinical events. Demographic data such as age at the time of transplant, gender, ethnicity, time posttransplantation, tacrolimus level, and induction therapy were correlated with Cylex levels. Cylex from children with an infection or acute rejection were compared to those from stable patients. All children received induction with basiliximab or thymoglobulin followed by a standard regimen with tacrolimus, steroids, and mycophenolate mofetil. Fifty-nine Cylex results were obtained in 44 pediatric renal transplant recipients. Cylex values ranged from 20 ng/mL to 728 ng/mL. We did not find significant correlation between any of the demographic characteristics studied (tacrolimus level, induction therapy, acute rejection, and Cylex levels). Fifteen patients had severe infections requiring hospitalization: 11 of 15 (73%) had Cylex<130 ng/mL; these levels differed significantly from those obtained in patients without infections. We concluded that clinical utility of Cylex is limited in children with kidney transplants because it did noes correlate with the prescribed dosage of medications or with rejection. However, low Cylex levels were highly correlated with serious infections.

Confronting the challenge: individualized immune monitoring after organ transplantation using the cellular immune function assay

The survival of a transplanted organ is dependent on avoidance of rejection, achieved through continuous immuno-suppression. Management of the transplant recipient confronts the clinician with a key challenge of post-transplant immune monitoring. Early detection of an activated allo-immune response is a harbinger of incipient rejection. Thus, timely intervention may prevent acute and chronic injury to the transplanted organ. Similarly, over immune-suppression can lead to infections or malignancies, hence the importance of early detection of the precarious suppression. The need for non-invasive systemic immune monitoring of the transplant recipient is therefore imperative. This review describes the cellular immune function assay--a non-invasive diagnostic method for evaluation of the net state of the recipient's cellular immune function. We describe the background that brought about the need for a reliable diagnostic tool for serial immune monitoring, and we overview the main mile-stones in the assimilation of the assay and its implementation in the clinic. The arising conclusion presents a novel non-invasive diagnostic bio-marker for post-transplant immune monitoring which enables the clinician to intervene prior to manifestation of clinical complications. The usefulness of the assay in detecting a state of over-suppression has been consensually described in multiple publications while its contribution in detection and management of under-suppression conditions remains to be determined by means of prospective interventional studies. The cellular immune function assay can be useful and beneficial for patient care only if used for longitudinal monitoring through serial testing.

Monitoring tolerance and rejection in organ transplant recipients

To avoid toxic side effects caused by permanent immunosuppressive treatment, research in transplantation focuses on new treatment strategies inducing tolerance or allowing drug weaning. Implementing drug minimization into clinical routine can be only safely achieved when guided by biomarkers reflecting the individual immune reactivity. We review recently described biomarkers and assays allowing identification of patients suitable for drug weaning or at risk of rejection. However, the majority of described biomarkers and assays have not been validated in prospective clinical trials. Thus, collaborative efforts are needed to design and perform prospective multicenter trials to validate the identified biomarkers across different laboratories.

The relationship between adenosine triphosphate within CD4(+) T lymphocytes and acute rejection after liver transplantation

BACKGROUND

There have been increasing interests in the relationship between CD4(+) T lymphocytes and acute rejection (AR) in transplantation. In this study, we explore the role of CD4(+) T lymphocytes after liver transplantation.

METHODS

  From February to October 2009, 87 patients underwent liver transplantation. They were divided into the AR group and non-acute rejection (NAR) group, with 56 healthy individuals in the control group. Blood specimens were collected preoperatively and at one, two, and four wk postoperatively for all groups and also on the day when AR occurred and one wk after intravenous glucocorticoid therapy for the AR group. Adenosine triphosphate (ATP) levels were measured using the ImmuKnow™ test kits for immune cell functions.

RESULTS

  After transplantation, the ATP levels within CD4(+) T lymphocytes were significantly elevated in the two groups when compared with the preoperative levels. It peaked in the AR group and was significantly higher than that of the NAR group (p < 0.05). By ROC curve analysis, the obvious elevation of the ATP value one wk after transplantation had better sensitivity and specificity in diagnosing the AR. The ATP sensitivity rate for early AR was 85.7% and specificity rate 80.9% when the cutoff value was 407 μg/L. The ATP value collected on the day of AR occurrence has apparently positive correlation with the rejection acting index (RAI) (p < 0.01). After the intravenous glucocorticoid therapy, all the ARs were reversed and the ATP value declined significantly compared with the control group and that on the day when AR occurred (p < 0.01).

CONCLUSIONS

  During the early postoperative period (especially at first week after liver transplantation), the elevation of ATP levels within CD4(+) T lymphocytes has good sensitivity and specificity in diagnosing the AR at early stage. And the degree of AR has positive relationship with ATP value. After the intravenous glucocorticoid therapy, the obvious declination of AR might be used in evaluating the effectiveness of anti-rejection treatment.

Peritransplant monitoring of immune cell function in adult living donor liver transplantation

PURPOSE

We evaluated the clinical utility of peritransplant in vitro assays of immune cell function in adult living donor liver transplant (LDLT) recipients.

METHODS

In particular, we measured immune cell function, using the ImmuKnow assay, in 107 adult LDLT recipients and 200 potential living liver donors (control group) admitted to our center between July 2008 and January 2009.

RESULTS

In the control group, the mean proportion of T-helper/inducer cells was 36.8% ± 8.2%. The degree of immune response was strong in 12%, moderate in 77%, and low in 11%. In the study group, the degree of immune response within the first month was strong in 4.6%, moderate in 38.2%, and low in 57.2%, thus significantly lower than in the control group (P < .001). ImmuKnow results and tacrolimus levels did not show a significant correlation (r(2) = .002, P = .392). Although six patients showed biopsy-proven acute cellular rejection, none showed a strong immune response. Patients with overt infection showed a lower immune response.

CONCLUSIONS

These results indicate that peritransplant assessment of immune response using the ImmuKnow assay does not reliably predict the occurrence of acute rejection. Additional studies are necessary to accurately assess the clinical utility of immune response monitoring.

Biomarkers as a tool for management of immunosuppression in transplant patients

Therapeutic drug monitoring is a well-established approach in transplantation medicine to guide immunosuppressive therapy. However, it cannot always predict the effects of immunosuppressive drugs on immune cells, because it does not reflect any aspect of an individual patient's immune system. Pharmacodynamic monitoring is a more recent strategy to provide information about the biologic effect of a specific drug or drug combination on the individual transplant patient. Currently, there is a large number of different biomarkers that either directly (specific markers) or indirectly (global markers) relate to the pharmacodynamic effects of immunosuppressive drugs and are under investigation as potential candidates to be introduced in clinical practice. Such biomarkers may be useful to identify patients at risk of developing acute rejection, infection, or cancer as well as patients who are suitable for minimization of immunosuppressant therapy and may be helpful to manage the timing and rate of immunosuppressant weaning. Serial longitudinal monitoring may allow maintenance of an individualized immunosuppressive regimen. Thus, biomarker monitoring is a potential complementary tool to therapeutic drug monitoring. This review summarizes the current state of knowledge about the use of a number of global or drug-specific pharmacodynamic biomarkers. It is not a comprehensive overview of the literature available, but rather an evidence-based reflection by experts who are intensively involved in scientific work in this field.

Immune response of young children using ATP-based Cylex assay: a brief report

Data on immune responses of young children using ATP release-based Cylex assay are insufficient. This study measured the immune response of healthy children less than three years of age to mitogens, PHA and Con-A. Blood was obtained from children attending routine health care visits. The Cylex assay was used to measure ATP production by CD4+ and CD3+ cells in response to PHA and Con-A, respectively. Samples from 20 children less than three years (range 10-27 months) were evaluated. The mean ATP production by CD4+ lymphocytes following PHA stimulation was 376 ng/mL (95% CI 17.1-735), which was similar to the response of older children in Hooper et al.'s (Clin Transplant 2005;19:834) study (p-value 0.28). The mean and median ATP production by CD3+ cells following Con-A stimulation were 114 ng/mL and 93.3 ng/mL, respectively (95% CI for median 45.2,148.6). The data suggest that although the immune system of young infants and toddlers is evolving, they are still able to respond to mitogen stimulation similar to older children.

Individualized immune monitoring of cardiac transplant recipients by noninvasive longitudinal cellular immunity tests

BACKGROUND

Common immunosuppression strategies after heart transplantation (HTx) are based on accepted target drug levels, disregarding that drug levels do not correlate with the individual patient's pharmacokinetics or with the actual immunosuppressive drug effect on the patient. The Immuknow assay is used for immune monitoring and management of organ transplant recipients. This study evaluated the Immuknow assay for longitudinal immune monitoring of HTx patients throughout various clinical settings.

METHODS

The functional immune response as measured by the Immuknow assay was determined in 327 samples collected from 50 HTx patients at the Rabin Medical Center and was analyzed together with common clinical parameters.

RESULTS

The median Immuknow levels measured throughout the infection episodes and the episodes of biopsy-proven acute rejection were 129 and 619 ng ATP/mL, respectively. These values were significantly dissimilar to the median Immuknow level measured during clinical quiescence, which was 351 ng ATP/mL (P<0.05). Calcineurin inhibitors drug-level measurements did not provide a reliable depiction of the patients' immune function, because the median deviation from the recommended drug trough levels range was significantly higher than the median deviation of Immuknow levels from their expected immune response zones. Longitudinal monitoring of Immuknow levels through serial testing proved to be a reliable method for individual patient immune management.

CONCLUSIONS

The Immuknow assay reliably reflects the cellular immune function of HTx patients, thereby supporting the immune monitoring and management of these patients. Serial longitudinal Immuknow monitoring allows immune management of therapy according to the individual patient's immune status.

Immune cell functional assay in monitoring of adult liver transplantation recipients with infection

PURPOSE

To identify the levels of functional immunity measured by the ImmuKnow assay in Chinese liver transplantation recipients and its application in monitoring the risk of posttransplant infection.

METHODS

Forty-five apparent healthy Chinese and 106 adult liver transplant (LT) recipients were under investigation. LTs were grouped in stable status or infection according to their clinical diagnosis. Whole blood samples were collected freshly and cultured within 6 hr, the CD4(+) T cells were selected, and their adenosine triphosphate (ATP) value was assayed the next day. Before stimulation, we also examined the percentage of T-helper (Th; CD3(+) CD4(+)) and T-suppress (Ts; CD3(+) CD8(+)) lymphocyte subpopulations and the ratio of Th/Ts.

RESULTS

The average ImmuKnow assay in infectious LT recipients was 128 + or - 84 ng/mL, significantly lower (P<0.05) than that in stable LTs (305 + or - 149 ng/mL) or in normal adults (301+ or - 101 ng/mL). The ImmuKnow values in LTs had a good negative correlation to infection clinically (r = -0.6217, P<0.001). Infectious risk was high when the ImmuKnow value was less than 130 ng/mL (odds ratio=13, 95% confidence interval 6.0-29.4, P<0.01). The sensitivity of low ImmuKnow values in posttransplant infection was 85.2%, significantly higher than those of Th/Ts ratio and immunosuppressant trough levels (P<0.01); specificity was 76.3%, comparable with that of Th/Ts ratio (75.5%), but greatly higher than immunosuppressant trough levels (P<0.01). ImmuKnow ATP values had no correlation with Th/Ts ratio or immunosuppressant trough levels.

CONCLUSION

ImmuKnow ATP levels are lower in LT recipients with infection, which provides a new tool in monitoring posttransplant infection, and an index of tailoring immunosuppression clinically.

Pretransplant immune risk assessment

PURPOSE OF REVIEW

Despite the introduction of advanced immunosuppressive drug therapies, clinical and subclinical rejections still occur in many graft recipients with a negative impact on the long-term transplant outcome. The immunological status of the patients awaiting the transplantation is a key factor for these processes. Here we summarize the recent efforts to identify and develop biomarkers and functional assays that allow an individual pretransplant risk assessment.

RECENT FINDINGS

New sensitive techniques assessing T-cell memory and B-cell activation have been developed. Furthermore, the expression level of soluble and molecular markers reflecting the activation state of the immune system and donor graft intrinsic factors have been shown to influence graft outcome.

SUMMARY

A variety of parameters and assays that determine the pretransplant immune activation status has been developed. Some of these assays have already been used prospectively to define high-risk patients receiving advanced immunosuppressive induction therapy.However, the conflicting results obtained in different studies show that biomarker analysis and functional assays performance need to be further standardized and validated in large prospective trials before they can be routinely implemented into a pretransplant risk assessment. Subsequently, a combined effort to design pretransplant risk stratification algorithms should lead to personalized immunosuppressive treatment regimes and improved graft survival and long-term graft function.

The impact of intercurrent EBV infection on ATP levels in CD4+ T cells of pediatric kidney transplant recipients

ImmuKnow measures ATP (ng/mL) in PHA-activated CD4+ T cells from patient's whole blood. According to published reports, median ImmuKnow is 258 ng/mL in stable pediatric kidney transplant (PKT) recipients > or =12 yr, and 165 ng/mL in those <12 yr. However, data on the effect of infection or AR on ImmuKnow are scarce. We studied the effect of Epstein-Barr virus (EBV) viremia on ImmuKnow in PKT with GD. Twenty-eight PKT with GD were reviewed. Group 1 has 19 PKT > or =12 yr, and group 2 has nine PKT <12 yr. Mean follow-up was 19.4 +/- 12 months. All ImmuKnow values discussed in this study were measured during GD +/- fever. None had ImmuKnow pretransplant. EBV DNA was isolated from patient blood by real-time PCR. Group 1 has eight boys and 11 girls (mean age = 16.6 +/- 2.4 yr). Group 2 has two boys and seven girls (mean age = 6 +/- 3.1 yr). Median ImmuKnow was 292 ng/mL in group 1, and 370 ng/mL in group 2. Nine children developed EBV viremia: two in group 1 (median ImmuKnow = 273 ng/mL), and seven in group 2 (median ImmuKnow = 475 ng/mL). Overall mean ImmuKnow in the nine EBV viremic patients was higher than that in the 19 non-viremic ones (422 +/- 176 ng/mL, and 302 +/- 113 ng/mL, respectively, unequal variance t-test, p = 0.08). Eight children developed AR (all in G1, median ImmuKnow = 272 ng/mL). In group 1, one patient developed concurrent EBV viremia and rejection, while another patient developed EBV viremia six months following a rejection episode. In group 2, none developed simultaneous AR, CMV, or BK virus infection with EBV viremia. None developed post-transplant lymphoproliferative disease. In summary, EBV viremia was paradoxically associated with high ImmuKnow in PKT <12 yr. This suggests strong co-stimulation of PHA-activated CD4+ T cells by EBV-transformed B cells.

The immunological monitoring of kidney and liver transplants in adult and pediatric recipients

Over the last half century, kidney and liver transplantation have been recognized as the treatment of choice for adult and children with end-stage renal or liver failure. Infants present a relative naïve immune system, but they are capable of mounting both cellular and humoral immune responses to the foreign antigens presented by the allograft. Immune monitoring is a way of measuring functional and molecular correlates of immune reactivity which may provide clinically useful information for identifying patients who have an increase risk of acute rejection prior to clinical symptoms or develop transplant tolerance. However, although numerous assays have been shown to predict rejection, to date no assays have been demonstrated to detect or predict transplantation tolerance. This is a summary of the published literature on promising antigen-specific and non-antigen-specific assays used for immunological monitoring in solid organ transplantation. This work also attempts to review their applicability to pediatric transplantation, specifically, pediatric kidney and liver recipients.

Assessment of CD4 T-lymphocyte reactivity by the Cylex ImmuKnow assay in patients following allogeneic hematopoietic SCT

After allogeneic hematopoietic SCT (alloHSCT), immunosuppressed patients are susceptible to opportunistic infections, and uncontrolled function of the graft can result in GVHD. Accurate immune monitoring may help early detection and treatment of these severe complications. Between October 2005 and November 2007, a total of 170 blood samples were collected from 40 patients after alloHSCT in the Hadassah Hebrew University Medical Center and from 13 healthy controls. We utilized the Cylex ImmuKnow assay for CD4 ATP levels to compare known clinically immunocompromised vs immunocompetent patients after alloHSCT. We also compared the reconstitution of WBC count to the ImmuKnow results and clinical status. The patients' clinical course correlated with the stratification of immune response established by the ImmuKnow assay for solid organ transplantation (immunocompetent vs immunocompromised), and this often differed from their WBC count. On the basis of our observations, we conclude that the ImmuKnow assay is a simple and fast immune-monitoring technique for patients undergoing alloHSCT, with potential to predict clinical course and facilitate prompt management of post-HSCT complications. The assay should be evaluated prospectively in clinical trials.

The impact of EBV load on T-cell immunity in pediatric thoracic transplant recipients

BACKGROUND

Immunologic monitoring of pediatric transplant (Tx) recipients, who are at increased risk of Epstein-Barr virus (EBV)-driven posttransplant lymphoproliferative disease, is an important goal in clinical transplantation. Here, we investigated the impact of EBV load on T-cell immunity from pediatric Tx recipients, using clinically applicable tests for improved assessment of T-cell immune competence.

METHODS

Thirty-five asymptomatic pediatric thoracic Tx patients were categorized into three groups according to their EBV load levels as follows: undetectable viral load (UVL), chronic low viral load (LVL) and chronic high viral load (HVL). Global and EBV-specific T-cell immunity were assessed by ATP release using Cylex Immuknow and T Cell Memory assays.

RESULTS

UVL patients exhibited normal ATP release to Concanavalin A (ConA) and phytohemagglutinin (PHA; 190+/-86 ng/mL, 328+/-163 ng/mL) and detectable EBV-specific (37+/-34 ng/mL) ATP responses. LVL patients displayed significantly stronger responses to ConA (373+/-174 ng/mL), PHA (498+/-196 ng/mL) and EBV (152+/-179 ng/mL), when compared with UVL or to HVL patients (ConA 185+/-114 ng/mL, PHA 318+/-173 ng/mL, and EBV 33+/-42 ng/mL). Moreover, HVL patients displayed significant inverse correlation between CD4+ T-cell ATP levels and EBV loads.

CONCLUSIONS

Evaluation of global and EBV-specific T-cell immunity provides a rapid assessment of patients' immune competence. It is still unclear whether selective oversuppressed ATP release by CD4+ T cells reflects HVL patients at risk of posttransplant lymphoproliferative disease. Further longitudinal studies will determine the importance of Immuknow test in identifying asymptomatic HVL patients vulnerable to EBV complications.

[Diagnosis and follow-up of chronic kidney graft dysfunction: from DFG to new biomarkers]

Chronic allograft dysfunction is an alteration of the renal graft's structure that causes renal function to deteriorate. It can be diagnosed histologically by the presence of interstitial fibrosis lesions and tubular atrophy beginning 3 months after transplantation. The predictive value of these lesions on graft loss is limited however. Kidney function is evaluated by measuring the glomerular filtration rate using reference methods such as urinary clearance of inulin. However, estimation of the glomerular filtration rate from plasma creatinine using the Cockroft or MDRD formulas is not a reliable marker of renal function loss in the transplantation patient; nor is it a good predictive marker of graft loss. To overcome the diagnostic and prognostic shortcomings of these traditional markers in transplantation patients, new biomarkers have been developed. Yet the advantages of these biomarkers in predicting the evolving complications of chronic allograft dysfunction as well as graft loss on the individual level now require validation.

Assessment of the Cylex ImmuKnow cell function assay in pediatric heart transplant patients

BACKGROUND

The Cylex ImmuKnow (Cylex, Columbia, MD) cell function assay (CICFA) is a commercially available test of immune response that purportedly identifies solid organ transplant patients at risk for either acute rejection (AR) or infection. Data on the utility of this test in pediatric heart transplant patients are very limited. This study tested the hypothesis that CICFA is a clinically useful test in this transplant population.

METHODS

All children undergoing heart transplantation at the study center (1989-2006) for whom CICFA levels were obtained were reviewed. The association of CICFA levels with episodes of AR and significant infections was determined.

RESULTS

Among 83 patients (34 girls, 41%), 367 CICFA levels were obtained (median, 4.0; interquartile range [IQR], 2.0-6.0 per patient). There were 26 episodes of AR in 17 patients (20%) and 38 infections in 34 patients (41%). CICFA levels were similar among patients with AR at the time of the CICFA measurement (median, 325 [IQR, 163-480] adenosine triphosphate [ATP] ng/ml) vs patients without AR (median, 330 [IQR, 227-441] ATP ng/ml; p = 0.36). CICFA levels were similar among patients with infections within 1 month of CICFA measurement (median, 295 [IQR, 216-366] ATP ng/ml) and those without infections (median, 330 [IQR, 226-453] ATP ng/ml; p = 0.24).

CONCLUSIONS

The CICFA is not predictive of AR or significant infections in pediatric heart transplant patients. On the basis of the available evidence, this assay cannot be recommended as part of the routine management of pediatric heart transplant patients.

Failure of immunosuppressive drug levels to predict T-cell reactivity in pediatric transplant patients

PURPOSE

In children, therapeutic management of immunosuppression relies on allograft function, drug levels, and clinical insight. Using a Food and Drug Administration-approved test for T-cell response, T-cell activation in vitro can be measured to monitor the immune response.

METHODS

In a retrospective study, 92 posttransplant children who received either a liver and/or kidney transplant and were followed by routine screening had their T-cell response tested by the Cylex ImmuKnow assay (Columbia, MD). After phytohemagglutinin-L stimulation of T-cells, adenosine triphosphate (ATP) concentrations were measured. In this assay, light emission at lambda = 562 nm is proportional to the ATP concentration (ng/mL). Immunosuppressive drug trough levels were also measured. Quantitative real-time polymerase chain reaction Epstein-Barr virus (EBV) viral titers were determined for 2 patients.

RESULTS

Separating the results into younger than 12 years and 12-year or older populations, we found that for the younger than 12 years, 28% of patients were in the low immune function category, 47% in the moderate, and 25% in the high category. For the 12 years or older, 25% of patients were in the low immune function category, 47% in the moderate, and 28% in the high category. The immune function distribution was not different (P = not significant) between the younger than 12 years and 12-year or older groups. Tacrolimus trough levels were 6.3 +/- 2.4 ng/mL for younger than 12 years and 5.6 +/- 3.3 ng/mL for 12 years or older (P = not significant), and rapamycin was similar, but both showed no correlation to immune function. We observed increased ATP values with decreased EBV viral loads.

CONCLUSIONS

These results suggest that tacrolimus and/or rapamycin levels do not adequately determine the biologic effect of immunosuppression. We expect that future T-cell activation monitoring will allow us to diminish rejection and infection events posttransplantation and lead to a healthier pediatric transplant population.

ImmuKnow: a new parameter in immune monitoring of pediatric liver transplantation recipients

Lifelong immunosuppression is mandatory for optimal graft and patient survival following liver transplantation. Nevertheless, graft rejection or numerous adverse events associated with overimmunosuppression or underimmunosuppression cannot be completely avoided. The ImmuKnow assay measures cell-mediated immunity and is able to discern between conditions of overimmunosuppression and underimmunosuppression. The aim of this study was to evaluate the ImmuKnow assay in the evaluation of the immune function in pediatric liver transplant recipients and to assess its correlation with the patients' clinical and biochemical status. Eighty-nine whole blood samples were collected from 23 liver transplant recipients that were 1 to 18 years old. The net state of immune function was determined by the quantitative measurement of the intracellular adenosine 5-triphosphate level in CD4+ lymphocytes after phytohemagglutinin stimulation. Comprehensive clinical data were correlated with the ImmuKnow assay results. In 23 of the 28 samples collected during clinical quiescence, ImmuKnow results were correlated with the clinical status, expressing the patient's moderate immune function. However, a correlation between measured therapeutic drug levels and clinical quiescence was found in only 18 of the 28 samples. In 6 patients who suffered from clinical complications, ImmuKnow measurements showed a wide range of deviations, expressing the unstable immunological status of these patients. In conclusion, the ImmuKnow assay correlates with the clinical status of liver-transplanted children. It serves as a reliable and unique parameter of the cellular immune function. We conclude that the ImmuKnow assay, together with existing clinical tools, may allow for the immune monitoring of pediatric liver recipients.

Infectious, malignant, and autoimmune complications in pediatric heart transplant recipients

OBJECTIVE

To review clinical courses of pediatric heart transplant survivors after 5 years from transplantation for infections, lymphoproliferative, and autoimmune diseases.

STUDY DESIGN

A total of 71 patients were examined in 2 groups, infant recipients (underwent transplant <1 year of age, n = 38) and older recipients (underwent transplant >1 year, n = 33). All patients received comparable immunosuppression. Calculated occurrence rates were reported as means per 10 years of follow-up with SEs. Differences were examined by using Poisson regression.

RESULTS

Infant recipients had significantly higher (P < .001) occurrence rates of severe (mean, 2.04 +/- 0.5) and chronic infections (mean, 4.58 +/- 0.67) compared with older recipients (means, 0.37 +/- 0.19 and 1.87 +/- 0.70, respectively). Types of infections were similar to those in the general population with extremely rare opportunistic infections; however, they were more severe and resistant to treatment. Autoimmune disorders occurred at a frequency comparable with lymphoproliferative diseases and were observed in 7 of 38 infants (18%). Most common were autoimmune cytopenias.

CONCLUSIONS

Infant heart transplant recipients who survive in the long term have higher occurrence rates of infections compared with older recipients. Autoimmune disorders are a previously unrecognized morbidity in pediatric heart transplantation.

The first year post-heart transplantation: use of immunosuppressive drugs and early complications

A large number of heart transplants are performed annually in different transplant centers in the United States. This is partly because of the improved survival of patients who undergo cardiac transplantation, thus making it a more viable option in the management of end-stage heart failure. The survival benefit after heart transplantation is a result of newer immunosuppressive drug regimens and a better understanding of their effects and interactions. Several studies, mostly involving a small number of patients, describe use and comparison of the many distinct immunosuppressive drugs available to date. Interestingly, many transplant centers perform in-house typical induction treatment regimens because of their own experience and intra-institutional preference. This review summarizes current practices of immunosuppressive drug therapy in the first year post-heart transplant based on the available clinical evidence and discusses future options of heart transplant immunosuppressive drug therapies.

Comparison of ATP production in whole blood and lymphocyte proliferation in response to phytohemagglutinin

Lymphocyte proliferation in response to mitogens, phytohemagglutinin (PHA), concanavalin A, pokeweed, and/or specific antigens has been the method of choice for in vitro diagnosis of cell-mediated immune dysfunction. Recently, an assay to measure intracellular adenosine triphosphate (ATP) production in response to PHA has been developed that requires a shorter, overnight incubation. We compared a standard 5- to 7-day lymphocyte mitogen stimulation assay utilizing tritiated thymidine (3H-thy) incorporation to one in which ATP production in response to PHA by CD4-positive cells is measured in a luminometer that requires only 18-24 hr. A total of 20 patient samples suspected of having decreased cell-mediated immunity submitted for mitogen induced lymphocyte proliferation and 21 normal controls were tested in both assays. A comparison of these two methods has demonstrated that the screening ATP assay has a sensitivity at 24 hr of 100% in detecting decreased PHA induced lymphocyte proliferation at 5 days and a specificity of 85% in the samples obtained from normal controls. The data indicate that the ATP assay may be a useful screening tool for more rapid detection of blood samples with decreased cell-mediated immune responses. However, a positive screen should always be confirmed by 3H-thy uptake using mitogens and recall antigens like candida and tetanus.

Posttransplant monitoring of pediatric lung transplant recipients

PURPOSE OF REVIEW

This article reviews current trends in pediatric lung posttransplant management, reveals pitfalls that exist, and introduces additional parameters that may have an impact on long-term survival.

RECENT FINDINGS

A number of parameters are monitored after transplantation to prevent or identify early complications related to lung transplantation in hope of reducing morbidity and mortality. These include routine laboratory studies, imaging, and monitoring of drug levels and lung function. Drug monitoring allows individualization of a patient's immunosuppressive therapy; however, drug levels alone may not reflect the patient's immune status. ImmuKnow is a general immune-monitoring assay that may help guide therapy. Two major complications are rejection and infection, and bronchoscopy is used to differentiate these two entities. Silent rejection may occur and increase the chance of developing bronchiolitis obliterans; therefore, many centers perform surveillance bronchoscopies. Recently, de-novo anti-histocompatibility locus antigen antibodies and gastroesophageal reflux have been associated with poor outcomes, and many centers are monitoring these entities as part of care following lung transplant.

SUMMARY

There has been little improvement in long-term outcomes of lung transplantation. Current monitoring methods are utilized to maintain or improve outcomes and recently additional monitoring parameters have been identified which hopefully will improve long-term outcomes.

Quantification of a low cellular immune response to aid in identification of pediatric liver transplant recipients at high-risk for EBV infection

OBJECTIVE

Uncontrolled EBV infection leading to lymphoproliferative disease is a significant cause of morbidity in pediatric orthotopic liver transplant (OLT) recipients. Herein, we describe the use of a novel immune assay, which quantifies the lymphocyte immune response and correlates the value to risk for EBV infection.

METHODS

All patient data were prospectively collected between 2003 and 2005. The study included 18 pediatric liver transplant recipients, seven males and 11 females with a mean follow-up of 47 months post-OLT. Patient EBV load was monitored using real-time quantitative PCR (qPCR). The ATP release (ng/mL) of CD3+ lymphocytes after mitogenic stimulation with phytohemagluttinin (PHA; Cylex Corporation) was used to quantitate patient immune response. Patients were stratified by EBV load: low (<1000 copies/microg DNA), medium (1000-4000 copies/microg DNA), and high (>4000 copies/microg DNA).

RESULTS

Patients with low EBV loads had a significantly (p < 0.04) stronger immune response to PHA than patients with EBV load >1000 copies/microg DNA. Further analysis demonstrated that patients with ATP level <125 ng/mL had 100% probability of an EBV titer >4000 copies/microg DNA, when compared with 22% if the ATP level was between 125 and 400 ng/mL or only 15% if >400 ng/mL (p < 0.05). When immunosuppression was reduced, we observed an increase of the ATP release that correlated with a decrease of the EBV viral load.

CONCLUSION

In conclusion, this study investigates the use of a lymphocyte activation assay to closely measure the immunosuppression status of pediatric liver transplant recipients. Because measurement of EBV DNA load as a single parameter has a poor positive predictive value for development of PTLD, the association of these assays may be of help in the identification of patients at risk for PTLD.

A novel approach to detect donor/recipent immune responses between HLA-identical pairs

Renal transplant rejection and graft versus host reactions between HLA genetically-identical sibling (HLAgi) donor/recipient (D/R) pairs are thought to result from minor histocompatibility antigen (mHAg) disparities. We have compared two methods of measuring HLAgi D/R T lymphocyte responses to "matured" dendritic cells: 1.) a modified Cylex assay of CD4(+) ATP levels (MLDC-ATP) versus 2.) (3)H-thymidine uptake (MLDC-(3)H). The MLDC-ATP kinetics peaked at 48 hours versus the MLDC-(3)H at 7 days, and appeared more sensitive. We tested HLAgi (normal) volunteer siblings (NLs), and D/R sibling pairs before and after renal transplantation (pre-Tx and post-Tx). The overall frequencies of positive responses in the MLDC-ATP for HLAgi NLs, pre-Tx, and post-Tx D/R pairs were 63%, 50%, and 42%, respectively. The percentage with reciprocal responses was 37.5%, 20%, and 22.22%, respectively. In one set of three HLAgi (NLs) siblings (two males and one female), there was a nongender-associated differential response. There was no MLDC correlation with class I MHC-associated mHAg (SSP) incompatibility, nor could some MLDC positive reactive pairs theoretically process the necessary HLA-class I restriction molecules for presentation of known (nanomeric) mHAg peptides. Speculatively, the MLDC reflects class II MHC-restricted mHAg reactions (not yet definable), with possible effects of other polymorphic (nonhistocompatibility) immune response genes, and thereby may be a useful measurement of CD4(+) T-cell HLAgi transplantation immunity.