Detection Of Acute Allograft Rejection Research Articles

Patient Specific Numerical Modeling for Renal Blood Monitoring Using Electrical Bio-Impedance.

Knowledge of renal blood circulation is considered as an important physiological value, particularly for fast detection of acute allograft rejection as well as the management of critically ill patients with acute renal failure. The electrical impedance signal obtained from kidney with an appropriate electrode system and optimal electrode system position regarding to the kidney projection on skin surface reflects the nature of renal blood circulation and tone of renal blood vessels. This paper proposes a specific numerical modelling based on prior information from MRI-data. The numerical modelling was conducted for electrical impedance change estimation due to renal blood distribution. The proposed model takes into the account the geometrical and electrophysiological parameters of tissues around the kidney as well as the actual blood distribution within the kidney. The numerical modelling had shown that it is possible to register the electrical impedance signal caused by renal blood circulation with an electrode system commensurate with the size of kidney, which makes it possible to reduce the influence of surrounding tissues and organs. Experimental studies were obtained to prove the numerical modelling and the effectiveness of developed electrode systems based on the obtained simulation results. The obtained electrical impedance signal with the appropriate electrode system shows very good agreement with the renal blood change estimated using Doppler ultrasound. For the measured electrical impedance signal, it is possible to obtain the amplitude-time parameters, which reflect the hemodynamic characteristics of the kidneys and used in diagnostics, which is the subject of further research.

Biological Variation of Donor-Derived Cell-Free DNA in Lung Transplant Recipients

Purpose Prior studies have demonstrated that percentage donor-derived cell-free DNA (%dd-cfDNA) in lung transplant patients may serve as a noninvasive marker of allograft injury and aid in the detection of acute allograft rejection, infection and chronic lung allograft dysfunction (CLAD). Clinical interpretation of %dd-cfDNA values require an understanding of its normal biological variation in stable lung transplant patients in order to identify abnormal results that may indicate the presence of allograft dysfunction. This study establishes the biological variation and reference change values (RCV) of %dd-cfDNA in lung transplant patients using an analytically validated assay with an established analytic coefficient of variation (CVA) of 6.8%. Methods Levels of plasma %dd-cfDNA (Allosure®) were analyzed from a cohort of patients at 4 lung transplant centers using %ddcfDNA as a method to monitor for allograft rejection in place of surveillance transbronchial biopsy. Patients with stable allograft function and ≥ 3 %dd-cfDNA samples were included. Stable patients were defined as having no evidence of infection, rejection, symptoms or documented decline in forced expiratory volume in 1 second (FEV1) > 10% from baseline. The AlloSure assay, a next-generation sequencing-based approach, was used to measure %dd-cfDNA in the plasma. Intraindividual coefficient of variation (CVI), interindividual CV (CVG), the index of individuality (II) and the RCV were calculated. Results 35 patients with a combined 124 %dd-cfDNA samples were included in the final analysis. 57% were men, the mean age was 59 years and 77% had bilateral lung transplants. The median %dd-cfDNA was 0.31% (interquartile range 0.18% - 0.68%), the 97.5th percentile and 95th percentile were 1.3% and 1.0% respectively. In 30 patients with an average of 3.7 tests, the CVI was 25%, the CVG was 19%, the II was 1.3 and the RCV was 72%. Conclusion In stable lung transplant patients, fluctuations in %dd-cfDNA levels of up 72% or levels less than 1% are within normal biological variation. With further validation, these thresholds may be incorporated into surveillance monitoring algorithms to identify potentially abnormal results indicating allograft dysfunction.

Renal Allograft Rejection: Noninvasive Ultrasound- and MRI-Based Diagnostics.

To date, allogeneic kidney transplantation remains the best available therapeutic option for patients with end-stage renal disease regarding overall survival and quality of life. Despite the advancements in immunosuppressive drugs and protocols, episodes of acute allograft rejection, a sterile inflammatory process, continue to endanger allograft survival. Since effective treatment for acute rejection episodes is available, instant diagnosis of this potentially reversible graft injury is imperative. Although histological examination by invasive core needle biopsy of the graft remains the gold standard for the diagnosis of ongoing rejection, it is always associated with the risk of causing substantial graft injury as a result of the biopsy procedure itself. At the same time, biopsies are not immediately feasible for a considerable number of patients taking anticoagulants due to the high risk of complications such as bleeding and uneven distribution of pathological changes within the graft. This can result in the wrong diagnosis due to the small size of the tissue sample taken. Therefore, there is a need for a tool that overcomes these problems by being noninvasive and capable of assessing the whole organ at the same time for specific and fast detection of acute allograft rejection. In this article, we review current state-of-the-art approaches for noninvasive diagnostics of acute renal transplant inflammation, i.e., rejection. We especially focus on nonradiation-based methods using magnetic resonance imaging (MRI) and ultrasound.

Right Ventricular Dysfunction as an Echocardiographic Measure of Acute Rejection Following Heart Transplantation in Children.

Noninvasive biomarkers of acute allograft rejection (AAR) following orthotopic heart transplantation (OHT) are needed. The aim of this study was to investigate the accuracy of echocardiographic (ECHO) right ventricular (RV) global functional and resistance indices in the detection of AAR. This retrospective chart review included children with biopsy-proven AAR (grade≥2R cellular or CD4+antibody-mediated rejection) following OHT and an ECHO within 12h of the biopsy. ECHO measures: (a) ratio of systolic to diastolic duration (S/D), (b) RV myocardial performance index (MPI) and (c) tricuspid regurgitant gradient to RV outflow tract velocity time integral ratio (TRG/VTI), were derived at baseline, during AAR and at two follow-ups. Sixteen patients [56% male, mean (SD) age at OHT 3.5 (4.3)years] had 16 AAR episodes. S/D (1.15 vs. 1.60, p<0.01), RV MPI (0.19 vs. 0.39, p<0.01) and TRG/VTI (1.05 vs. 1.7, p=0.01) deteriorated during AAR and, except for diastolic duration, improved significantly at first follow-up. The negative predictive values for S/D, RV MPI and TRG/VTI at cutoffs of 1.3, 0.31 and 1.3 were 97, 97 and 87%, respectively. RV S/D, MPI and TRG/VTI deteriorated during AAR. Their excellent negative predictive values suggest that their incorporation in surveillance may obviate the need for routine biopsies.

Imaging-based diagnosis of acute renal allograft rejection.

Kidney transplantation is the best available treatment for patients with end stage renal disease. Despite the introduction of effective immunosuppressant drugs, episodes of acute allograft rejection still endanger graft survival. Since efficient treatment of acute rejection is available, rapid diagnosis of this reversible graft injury is essential. For diagnosis of rejection, invasive core needle biopsy of the graft is the "gold-standard". However, biopsy carries the risk of significant graft injury and is not immediately feasible in patients taking anticoagulants. Therefore, a non-invasive tool assessing the whole organ for specific and fast detection of acute allograft rejection is desirable. We herein review current imaging-based state of the art approaches for non-invasive diagnostics of acute renal transplant rejection. We especially focus on new positron emission tomography-based as well as targeted ultrasound-based methods.

Noninvasive assessment for acute allograft rejection in a rat lung transplantation model.

After lung transplantation, early detection of acute allograft rejection is important not only for timely and optimal treatment, but also for the prediction of chronic rejection which is a major cause of late death. Many biological and immunological approaches have been developed to detect acute rejection; however, it is not well known whether lung mechanics correlate with disease severity, especially with pathological rejection grade. In this study, we examined the relationship between lung mechanics and rejection grade development in a rat acute rejection model using the forced oscillation technique, which provides noninvasive assessment of lung function. To this end, we assessed lung resistance and elastance (RL and EL) from implanted left lung of these animals. The perivascular/interstitial component of rejection severity grade (A‐grade) was also quantified from histological images using tissue fraction (TF; tissue + cell infiltration area/total area). We found that TF, RL, and EL increased according to A‐grade. There was a strong positive correlation between EL at the lowest frequency (Elow; EL at 0.5 Hz) and TF (r2 = 0.930). Furthermore, the absolute difference between maximum value of EL (Emax) and Elow (Ehet; Emax − Elow) showed the strong relationship with standard deviation of TF (r2 = 0.709), and A‐grade (Spearman's correlation coefficients; rs = 0.964, P < 0.0001). Our results suggest that the dynamic elastance as well as its frequency dependence have the ability to predict A‐grade. These indexes should prove useful for noninvasive detection and monitoring the progression of disease in acute rejection.

SPECT- and PET-based approaches for noninvasive diagnosis of acute renal allograft rejection.

Molecular imaging techniques such as single photon emission computed tomography (SPECT) or positron emission tomography are promising tools for noninvasive diagnosis of acute allograft rejection (AR). Given the importance of renal transplantation and the limitation of available donors, detailed analysis of factors that affect transplant survival is important. Episodes of acute allograft rejection are a negative prognostic factor for long-term graft survival. Invasive core needle biopsies are still the “goldstandard” in rejection diagnostics. Nevertheless, they are cumbersome to the patient and carry the risk of significant graft injury. Notably, they cannot be performed on patients taking anticoagulant drugs. Therefore, a noninvasive tool assessing the whole organ for specific and fast detection of acute allograft rejection is desirable. We herein review SPECT- and PET-based approaches for noninvasive molecular imaging-based diagnostics of acute transplant rejection.

Remote noninvasive allograft rejection monitoring for heart transplant recipients: study protocol for the novel evaluation with home electrocardiogram and remote transmission (NEW HEART) study

BackgroundAcute allograft rejection is a major cause of early mortality in the first year after heart transplantation in adults. Although endomyocardial biopsy (EMB) is not a perfect "gold standard" for a correct diagnosis of acute allograft rejection, it is considered the best available test and thus, is the current standard practice. Unfortunately, EMB is an invasive and costly procedure that is not without risk. Recent evidence suggests that acute allograft rejection causes delays in ventricular repolarization and thereby increases the cellular action potential duration resulting in a longer QT interval on the electrocardiogram (ECG). No prospective study to date has investigated whether such increases in the QT interval could provide early detection of acute allograft rejection. Therefore, in the Novel Evaluation With Home Electrocardiogram And Remote Transmission (NEW HEART) study, we plan to investigate the potential benefit of daily home QT interval monitoring to predict acute allograft rejection.Methods/designThe NEW HEART study is a prospective, double-blind, multi-center descriptive research study. A sample of 325 adult heart transplant recipients will be recruited within six weeks of transplant from three sites in the United States. Subjects will receive the HeartView™ ECG recorder and its companion Internet Transmitter, which will transmit the subject's ECG to a Core Laboratory. Subjects will be instructed to record and transmit an ECG recording daily for 6 months. An increase in the QTC interval from the previous day of at least 25 ms that persists for 3 consecutive days will be considered abnormal. The number and grade of acute allograft rejection episodes, as well as all-cause mortality, will be collected for one year following transplant surgery.DiscussionThis study will provide "real world" prospective data to determine the sensitivity and specificity of QTC as an early non invasive marker of cellular rejection in transplant recipients during the first post-transplant year. A non-invasive indicator of early allograft rejection in heart transplant recipients has the potential to limit the number and severity of rejection episodes by reducing the time and cost of rejection surveillance and by shortening the time to recognition of rejection.Trial RegistrationClinicalTrials.gov: NCT01365806

Utilidad de la prueba de troponina T de alta sensibilidad en la detección de rechazo agudo en trasplante cardiaco

Introduction and objectives Detection of acute allograft rejection in heart transplant recipients by noninvasive methods is a challenge in the management of these patients. In this study, the usefulness of a new highly sensitive method for the measurement of troponin T is evaluated. Methods We designed a case-crossover study, in which each patient served as his or her own control, by selecting samples from treated acute rejection episodes (29 cases) and samples obtained immediately before and/or after rejection (38 controls). The highly sensitive troponin T was measured by a new pre-commercial test (Elecsys Troponin T HS). Results In all samples, highly sensitive troponin T was detectable, with a median of 0.068 ng/L (IQR, 0.030-0.300 ng/L). The levels correlated with right atrial pressure (r=0.37; P=.002), N-terminal pro-brain natriuretic peptide concentration (r=0.67; P<.001), and time since transplantation (r=–0.81; P<.001). The highly sensitive troponin T concentrations were higher in patients with rejection (0.155 ng/mL vs 0.047 ng/mL; P=.006). In the receiver operating characteristic analysis, the area under the curve was 0.67 (95% confidence interval, 0.53-0.77) and the best cutoff was 0.035 ng/mL, which was associated with rejection (odds ratio=3.7; 95% confidence interval, 1.2-11.9; P=.02). By restricting the analysis to the first 2 months, the area under the curve increased to 0.86 (95% confidence interval 0.66-0.97), with an optimal cutoff of 1.10 ng/mL (S=58% [28%-85%]; E=100% [74%-100%]). Conclusions Troponin T was detectable in all samples when a new highly sensitive assay was used, and at higher concentrations in the presence of acute rejection; however, the usefulness of this test in patient management is limited to support for clinical or histological suspicion of rejection, especially in the early post-transplant period. Full English text available from: www.revespcardiol.org

Usefulness of High Sensitivity Troponin T Assay in Detecting Acute Allograft Rejection After Heart Transplantation

Introduction and objectives Detection of acute allograft rejection in heart transplant recipients by noninvasive methods is a challenge in the management of these patients. In this study, the usefulness of a new highly sensitive method for the measurement of troponin T is evaluated. Methods We designed a case-crossover study, in which each patient served as his or her own control, by selecting samples from treated acute rejection episodes (29 cases) and samples obtained immediately before and/or after rejection (38 controls). The highly sensitive troponin T was measured by a new pre-commercial test (Elecsys Troponin T HS). Results In all samples, highly sensitive troponin was detectable, with a median of 0.068 ng/mL (IQR, 0.030-0.300 ng/mL). The levels correlated with right atrial pressure (r = 0.37; P = .002), N-terminal pro-brain natriuretic peptide concentration (r = 0.67; P < .001), and time since transplantation (r = –0.81; P < .001). The highly sensitive troponin concentrations were higher in patients with rejection (0.155 ng/mL vs 0.047 ng/mL; P = .006). In the receiver operating characteristic analysis, the area under the curve was 0.67 (95% confidence interval, 0.53-0.77) and the best cutoff was 0.035 ng/mL, which was associated with rejection (odds ratio = 3.7; 95% confidence interval, 1.2-11.9; P = .02). By restricting the analysis to the first 2 months, the area under the curve increased to 0.86 (95% confidence interval 0.66-0.97), with an optimal cutoff of 1.10 ng/mL (S = 58% [28%-85%]; E = 100% [74%-100%]). Conclusions Troponin T was detectable in all samples when a new highly sensitive assay was used, and at higher concentrations in the presence of acute rejection; however, the usefulness of this test in patient management is limited to support for clinical or histological suspicion of rejection, especially in the early post-transplant period.

19F MRI detection of acute allograft rejection with in vivo perfluorocarbon labeling of immune cells

Current diagnosis of organ rejection following transplantation relies on tissue biopsy, which is not ideal due to sampling limitations and risks associated with the invasive procedure.We have previously shown that cellular magnetic resonance imaging (MRI) of iron-oxide labeled immune-cell infiltration can provide a noninvasive measure of rejection status by detecting areas of hypointensity on T 2*-weighted images. In this study, we tested the feasibility of using a fluorine-based cellular tracer agent to detect macrophage accumulation in rodent models of acute allograft rejection by fluorine-19 ((19) F) MRI and magnetic resonance spectroscopy. This study used two rat models of acute rejection, including abdominal heterotopic cardiac transplant and orthotopic kidney transplant models. Following in vivo labeling of monocytes and macrophages with a commercially available agent containing perfluoro-15-crown-5-ether, we observed (19) F-signal intensity in the organs experiencing rejection by (19) F MRI, and conventional (1) H MRI was used for anatomical context. Immunofluorescence and histology confirmed macrophage labeling. These results are consistent with our previous studies and show the complementary nature of the two cellular imaging techniques. With no background signal, (19) F MRI/magnetic resonance spectroscopy can provide unambiguous detection of fluorine labeled cells, and may be a useful technique for detecting and quantifying rejection grade in patients.

Noninvasive Evaluation of Cardiac Allograft Rejection by Cellular and Functional Cardiac Magnetic Resonance

We sought to use cardiac magnetic resonance (CMR) to establish sensitive and reliable indexes for noninvasive detection of acute cardiac allograft rejection. Appropriate surveillance for acute allograft rejection is vitally important for graft survival. The current gold standard for diagnosing and staging rejection after organ transplantation is endomyocardial biopsy, which is not only invasive but also prone to sampling errors. The motivation of this study is to establish a CMR-based alternative that is noninvasive and sensitive for early detection of allograft rejection before irreversible damage occurs. We employed a noninvasive 2-pronged approach to detect acute cardiac allograft rejection using a rodent working heart and lung transplantation model. We used CMR to detect immune-cell infiltration at sites of rejection by monitoring the accumulation of dextran-coated ultra-small superparamagnetic-iron-oxide-labeled immune cells (in particular macrophages) in vivo. Simultaneously, we used CMR tagging and strain analysis to detect regional myocardial function loss resulting from acute rejection. Immune cells infiltration, mainly macrophages and monocytes, could be identified with CMR by in vivo labeling with ultra-small superparamagnetic-iron-oxide. Our data show that immune-cell infiltration in cardiac allograft rejection was highly heterogeneous. Thus, it is not surprising to find inconsistencies between rejection and endomyocardial biopsy results because of the limited number and small samples available. Tagged CMR and strain analysis showed that, as with immune-cell infiltration, ventricular functional loss was also heterogeneous. Although changes in global systolic function were generally not observed until the later stages of rejection, our data revealed that a functional index derived from local strain analysis correlated well with rejection grades, which may be a more sensitive parameter for detecting early rejection. CMR is noninvasive and provides a 3-dimensional, whole-heart perspective of the rejection status, potentially allowing more reliable detection of acute allograft rejection.

Strain and Strain Rate Imaging by Echocardiography - Basic Concepts and Clinical Applicability

Echocardiographic strain and strain-rate imaging (deformation imaging) is a new non-invasive method for assessment of myocardial function. Due to its ability to differentiate between active and passive movement of myocardial segments, to quantify intraventricular dyssynchrony and to evaluate components of myocardial function, such as longitudinal myocardial shortening, that are not visually assessable, it allows comprehensive assessment of myocardial function and the spectrum of potential clinical applications is very wide. The high sensitivity of both tissue Doppler imaging (TDI) derived and two dimensional (2D) speckle tracking derived myocardial deformation (strain and strain rate) data for the early detection of myocardial dysfunction recommend these new non-invasive diagnostic methods for extensive clinical use. In addition to early detection and quantification of myocardial dysfunction of different etiologies, assessment of myocardial viability, detection of acute allograft rejection and early detection of allograft vasculopathy after heart transplantation, strain and strain rate data are helpful for therapeutic decisions and also useful for follow-up evaluations of therapeutic results in cardiology and cardiac surgery. Strain and strain rate data also provide valuable prognostic information, especially prediction of future reverse remodelling after left ventricular restoration surgery or after cardiac resynchronization therapy and prediction of short and median-term outcome without transplantation or ventricular assist device implantation of patients referred for heart transplantation.The Review explains the fundamental concepts of deformation imaging, describes in a comparative manner the two major deformation imaging methods (TDI-derived and speckle tracking 2D-strain derived) and discusses the clinical applicability of these new echocardiographic tools, which recently have become a subject of great interest for clinicians.

Usefulness and limitations of transthoracic echocardiography in heart transplantation recipients

Transthoracic echocardiography is a primary non-invasive modality for investigation of heart transplant recipients. It is a versatile tool which provides comprehensive information about cardiac structure and function. Echocardiographic examinations can be easily performed at the bedside and serially repeated without any patient's discomfort. This review highlights the usefulness of Doppler echocardiography in the assessment of left ventricular and right ventricular systolic and diastolic function, of left ventricular mass, valvular heart disease, pulmonary arterial hypertension and pericardial effusion in heart transplant recipients. The main experiences performed by either standard Doppler echocardiography and new high-tech ultrasound technologies are summarised, pointing out advantages and limitations of the described techniques in diagnosing acute allograft rejection and cardiac graft vasculopathy. Despite the sustained efforts of echocardiographic technique in predicting the biopsy state, endocardial myocardial biopsies are still regarded as the gold standard for detection of acute allograft rejection. Conversely, stress echocardiography is able to identify accurately cardiac graft vasculopathy and has a recognised prognostic in this clinical setting. A normal stress-echo justifies postponement of invasive studies. Another use of transthoracic echocardiography is the monitorisation and the visualisation of the catheter during the performance of endomyocardial biopsy. Bedside stress echocardiography is even useful to select appropriately heart donors with brain death. The ultrasound monitoring is simple and effective for monitoring a safe performance of biopsy procedures.

Non-Invasive Detection of Acute Allograft Rejection in Children by Tissue Doppler Imaging: Myocardial Velocities and Myocardial Acceleration During Isovolumic Contraction

In adults, an acute decrease of regional myocardial velocities is a sensitive marker of rejection. In children, velocities are more variable. A new marker, myocardial acceleration during isovolumic contraction (IVA), appears to be less age-dependent than myocardial velocities. This study therefore compared tissue Doppler (TDI)-derived velocities and IVA as potential rejection markers for children. TDI was performed in 15 pediatric heart transplant recipients (age 8.0 +/- 3.6 years) during acute rejection and at baseline without rejection, 50 additional transplant children without rejection (7.8 +/- 5.9 years) and 30 age-matched healthy children (7.5 +/- 5.2 years). Color Doppler cine-loops of 3 cardiac cycles were stored as echocardiographic raw data. Using off-line post-processing, systolic (S) and diastolic (E) myocardial velocities and IVA were measured in 5 basal left ventricular segments. IVA is the peak isovolumic contraction wave velocity divided by acceleration time. Without rejection, transplant children had significantly lower diastolic velocities (basal lateral E 10.4 +/- 2.9 vs 11.9 +/- 2.6 cm/s; p < 0.001) and systolic velocities (S 5.6 +/- 1.4 vs 7.1 +/- 2.0 cm/s; p < 0.001) than normal age-matched controls, but IVA was similar (1.2 +/- 1.4 vs 1.3 +/- 0.5 m/s2). During rejection, all markers decreased significantly compared with age-matched normal control, the non-rejecting transplant group and individual baseline values. Regional myocardial velocities change significantly during acute allograft rejection in children. However, many children already have wall motion abnormalities at baseline, so results are often difficult to interpret. In contrast, isovolumic acceleration was normal without rejection and selectively decreased during the event. IVA is a promising non-invasive rejection marker for pediatric patients.

Early detection of acute allograft rejection by linear and nonlinear analysis of heart rate variability

Objective: The first months after orthotopic heart transplantation are associated with the highest risk of acute allograft rejection. This study explores the utility and reliability of linear and novel nonlinear metrics of heart rate variability as predictors of graft rejection. The underlying hypothesis is that the transplanted heart, in response to inflammatory mediators, alters the dynamic properties of its rhythm-generating system. Methods: In a cross-sectional study of 45 patients who had undergone heart transplantation, spanning a period of 4 months after the operation, heart rate variability was examined by time- and frequency-domain analysis. The nonlinear features of heart rate variability were studied by computing a pointwise correlation dimension of R-R interval time series. The results of heart rate variability analysis were compared with those of endomyocardial surveillance biopsy studies using the International Society for Heart and Lung Transplantation scoring system. Results: Duration of heart transplantation itself exhibited a significant (P < .05) association with the onset of rejection. Specific predictors of acute rejection based on heart rate variability were identified, including shortening of the R-R interval (from 700 ± 68 to 648 ± 72 ms), an increase in the ratio of low-frequency (0.04-0.15 Hz) to high-frequency (0.15-0.40 Hz) spectral power (from 0.3 ± 0.2 to 0.6 ± 0.4), and a decrease in pointwise correlation dimension values (from 1.7 ± 0.7 to 0.9 ± 0.3 units). Multivariable logistic regression analysis (R2 = 0.4) revealed that the only significant independent risk predictors were pointwise correlation dimension (odds ratio, 2.2 per 0.1 unit) and duration of heart transplantation (odds ratio, 1.7 per week). Conclusion: Nonlinear measures of heart rate variability provide noninvasive means for identifying patients undergoing cardiac transplantation with acute rejection, thereby enabling the assessment of the time-dependent adaptive response of the donor heart to its host. (J Thorac Cardiovasc Surg 2000;120:737-45)

Circulating interleukin-1 receptor antagonist (IL-1RA) serum levels in patients undergoing orthotopic heart transplantation.

In a pilot study we determined the serum levels of circulating interleukin-1 receptor antagonist (IL-1ra) in patients undergoing orthotopic heart transplantation and in control patients scheduled for open heart surgery without allograft transplantation. Blood samples were obtained from 12 transplant recipients and 7 controls prior to the operative procedures to determine baseline values. Serum levels of IL-1ra were measured within 12 h of decrossclamping of the aorta and every 24 h for the following 14 days. Endomyocardial biopsies were obtained weekly for the 1st month after transplantation. Compared to baseline values, IL-1ra serum levels 12 h after decrossclamping of the aorta were significantly higher both in the control group (507 +/- 165 vs 3980 +/- 452 pg/ml, P < 0.01) and among the transplant recipients (413 +/- 180 vs 4117 +/- 459 pg/ml, P < 0.01) IL-1ra levels remained significantly elevated for 2 and 5 days, respectively. There were no significant differences in the IL-1ra serum levels between the two groups throughout the observation period. Endomyocardial biopsies of two patients showed acute allograft rejection, Billingham grade IIIa and IIIb, respectively. In both cases, the rejection episodes were accompanied by a renewed and more pronounced elevation in the IL-1ra serum levels beyond 4000 pg/ml for at least 2 days. These preliminary results indicate that IL-1ra may be a nonspecific immune marker during the first few days after orthotopic heart transplantation and cardiopulmonary bypass. Moreover, renewed, prolonged increases in IL-1ra appear to be associated with rejection. Further studies are needed to confirm the predictive value of IL-1ra in the detection of acute allograft rejection.

Circulating interleukin-1 receptor antagonist (IL-1RA) serum levels in patients undergoing orthotopic heart transplantation

Abstract In a pilot study we determined the serum levels of circulating interleukin-1 receptor antagonist (IL-1ra) in patients undergoing orthotopic heart transplantation and in control patients scheduled for open heart surgery without allograft transplantation. Blood samples were obtained from 12 transplant recipients and 7 controls prior to the operative procedures to determine baseline values. Serum levels of IL-1ra were measured within 12 h of decrossclamping of the aorta and every 24 h for the following 14 days. Endomyocardial biopsies were obtained weekly for the 1st month after transplantation. Compared to baseline values, IL-1ra serum levels 12 h after decrossclamping of the aorta were significantly higher both in the control group (507 ± 165 vs 3980 ± 452 pg/ml, P < 0.01) and among the transplant recipients (413 ± 180 vs 4117 ± 459 pg/ml, P < 0.01) IL-1ra levels remained significantly elevated for 2 and 5 days, respectively. There were no significant differences in the IL-1ra serum levels between the two groups throughout the observation period. Endomyocardial biopsies of two patients showed acute allograft rejection, Billingham grade IIIa and IIIb, respectively. In both cases, the rejection episodes were accompanied by a renewed and more pronounced elevation in the IL-1ra serum levels beyond 4000 pg/ml for at least 2 days. These preliminary results indicate that IL-1ra may be a nonspecific immune marker during the first few days after orthotopic heart transplantation and cardiopulmonary bypass. Moreover, renewed, prolonged increases in IL-1ra appear to be associated with rejection. Further studies are needed to confirm the predictive value of IL-1ra in the detection of acute allograft rejection.

NITRIC OXIDE GENERATION

The L-arginine:nitric oxide (NO) biosynthetic pathway has been proposed as an important mediator in host defense mechanisms and may therefore play a role in the acute allograft response. We have studied NO generation in liver allograft rejection and determined its value in immunological monitoring. Stable end products of this pathway have been determined serially in 50 primary liver recipients and compared with 2 known mediators and markers of acute allograft rejection (IL-2R positive lymphocytes and circulating TNF alpha). Plasma concentrations of acid-labile nitrosocompounds (NOx), which increased during acute allograft rejection (P < 0.0001), correlated with rejection severity and were reduced after administration of supplemental high dose glucocorticoids. Concentrations were significantly lower in nonrejection graft complications but were elevated during episodes of sepsis. Correlations between plasma NOx levels and circulating TNF-alpha (r = 0.451, P < 0.001) and IL-2R-positive lymphocytes in peripheral blood (r = 0.781, P < 0.001) were demonstrated. In a logistic analysis of these variables, plasma NOx was the most predictive parameter of an episode of acute cellular rejection. Nitric oxide generation in FK506-treated patients was lower compared with patients receiving a CsA-based immunosuppression regimen and was associated with a reduced frequency of acute rejection in the FK506 group. These data are consistent with a role for NO in the cellular alloantigen immune response and indicate that monitoring of plasma levels of NOx may be useful in the detection of acute allograft rejection.

Early detection of acute allograft rejection in rat heart transplantation: flowcytometric monitoring of interleukin 2 receptor expression on CD8 positive lymphocytes.

To assess the usefulness of flowcytometric monitoring in the early detection of acute allograft rejection, we studied surface markers of graft infiltrating lymphocytes, coronary sinus blood lymphocytes and peripheral blood lymphocytes after rat heart transplantation. Fisher rats served as donors and Lewis rats as recipients. Among recipients that received no immunosuppression, grafts were removed 2 days after transplantation (Ongoing Rejection Group: n = 7) and on the day of terminal rejection (Rejection Group: n = 7). The Immunosuppression Group (n = 7) was treated with cyclosporine A at a dose of 3 mg/kg/day intramuscularly for 14 days. The following two color analyses were studied: OX8 (anti-CD8) with OX39 (anti-interleukin 2 receptor; IL2R), W3/25 (anti-CD4) with OX39, W3/25 with OX8. Histological grading demonstrated no significant difference between the Ongoing Rejection Group and the Immunosuppression Group, which showed mild rejection (1.29 +/- 0.27 versus 1.14 +/- 0.24). The proportion of CD8(+)IL2R(+) graft infiltrating lymphocytes showed a more significant increase in the Ongoing Rejection Group than in the Immunosuppression Group (32.1 +/- 3.05 versus 20.6 +/- 9.02; p < 0.01). The proportion of CD8(+) IL2R(+) coronary sinus blood lymphocytes also showed significant increase in the Ongoing Rejection Group compared with the Immunosuppression Group (4.63 +/- 1.91 versus 2.52 +/- 1.60; p < 0.05). These results suggest that this technique can detect acute allograft rejection earlier than endomyocardial biopsy, before the phase in which histological findings become evident.