Resolution Of Acute Rejection Research Articles

347.1: Unraveling the Stage-Shift of Acute Rejection in Renal Allografts

Introduction: The lack of accuracy in current allograft monitoring methodologies for allograft monitoring underscores a critical unmet need for more accurate immunosurveillance to uncover the flux in alloimmunity. QSant – a non-invasive, urine based multi-analyte diagnostic test – was clinically validated to prognosticate injury, risk of evolution, and resolution of acute rejection. QScore—the composite score across measurements of DNA markers: the amount of cell-free DNA, fraction of methylated cfDNA, protein and metabolic biomarkers in the QSant assay—enables this risk prognostication. This study now explores the clinical utility of QSant across the alloimmunity gradient of 32–100 for the early diagnosis of allograft injury and rejection. Methods: Utilizing a large real-world dataset of contemporaneous kidney allograft biopsy and QSant data from 11 US kidney transplant centers, the QScore offers a dynamic view into the changing state of allograft injury and rejection in response to alterations in the patients’ immunosuppression regimen. First analysis included Q-Score distributions in the biopsy-paired validation (n = 162) and prediction (n = 91) data from the Yang cohort, which were collected between 2010 and 2018 [10]. Second was a new analysis of a real-world data (RWD) cohort, comprising of prospectively collected urine samples (n = 235). Results: The RWD cohort (n = 235) of both adult and pediatric renal transplant patients demonstrated a spectrum across the Q-Score distribution. Specifically, 37.9% of the samples were enriched for immune quiescence (Q-Score < 32); the remaining 62.1% were enriched for the injury/rejection spectrum (Q-Score ≥ 32). The QScore <32 classifies stable allograft recipients; QScore between 32-55 exposes a state of alloimmunity flux; and the score between 55-100 provides advanced alloimmunity. Serial monitoring by QSant across a subset of 32 patients (RWD cohort,) over a period of two consecutive quarters (timepoints 1 and 2), captures the essence of the alloimmunity flux (p-value: 0.086 by non-parametric Wilcoxon test). Patients in the immunoquiescent domain (31% [10/32]) by and large continue to be stable (with Q-Scores that track at <32) 22% [7/32]). However, 9.4% (3/32) of patients show Q-Score drifts above 32 with evidence of early rejection. Patients in the alloimmune injury domain follow three trajectories: i) a planar gradient in QScore across time, showing persistence of alloimmunity; ii) an increasing gradient, delineating patients moving into the mature acute rejection domain; iii) a decreasing gradient, delineating patients moving into the immunoquiescent domain, putatively in response to immunomodulation following assessment of active rejection (Figure 1). Conclusion: The observed alloimmunity flux suggested precision monitoring with QSant has the potential to differentiate higher-grade acute rejection episodes from sub-clinical rejection, thereby improving a transplant recipient’s’ quality of life.

Through the Looking Glass: Unraveling the Stage-Shift of Acute Rejection in Renal Allografts.

Sub-optimal sensitivity and specificity in current allograft monitoring methodologies underscore the need for more accurate and reflexive immunosurveillance to uncover the flux in alloimmunity between allograft health and the onset and progression of rejection. QSant—a urine based multi-analyte diagnostic test—was developed to profile renal transplant health and prognosticate injury, risk of evolution, and resolution of acute rejection. Q-Score—the composite score, across measurements of DNA, protein and metabolic biomarkers in the QSant assay—enables this risk prognostication. The domain of immune quiescence—below a Q-Score threshold of 32—is well established, based on published AUC of 98% for QSant. However, the trajectory of rejection is variable, given that causality is multi-factorial. Injury and subtypes of rejection are captured by the progression of Q-Score. This publication explores the clinical utility of QSant across the alloimmunity gradient of 32–100 for the early diagnosis of allograft injury and rejection.

Acute and Chronic Rejection: Compartmentalization and Kinetics of Counterbalancing Signals in Cardiac Transplants

Acute and chronic rejection impact distinct compartments of cardiac allografts. Intramyocardial mononuclear cell infiltrates define acute rejection, whereas chronic rejection affects large arteries. Hearts transplanted from male to female C57BL/6 mice undergo acute rejection with interstitial infiltrates at 2 weeks that resolve by 6 weeks when large arteries develop arteriopathy. These processes are dependent on T cells because no infiltrates developed in T cell-deficient mice and transfer of CD4 T cells restored T cell as well as macrophage infiltrates and ultimately neointima formation. Markers of inflammatory macrophages were up-regulated in the interstitium acutely and decreased as markers of wound healing macrophages increased chronically. Programmed cell death protein, a negative costimulator, and its ligand PDL1 were up-regulated in the interstitium during resolution of acute rejection. Blocking PDL1:PD1 interactions in the acute phase increased interstitial T cell infiltrates. Toll-like receptor (TLR) 4 and its endogenous ligand hyaluronan were increased in arteries with neointimal expansion. Injection of hyaluronan fragments increased intragraft production of chemokines. Our data indicate that negative costimulatory pathways are critical for the resolution of acute interstitial infiltrates. In the arterial compartment recognition of endogenous ligands including hyaluronan by the innate TLRs may support the progression of arteriopathy.

Monocytic Tissue Transglutaminase in a Rat Model for Reversible Acute Rejection and Chronic Renal Allograft Injury.

Acute rejection is a major risk factor for chronic allograft injury (CAI). Blood leukocytes interacting with allograft endothelial cells during acute rejection were suggested to contribute to the still enigmatic pathogenesis of CAI. We hypothesize that tissue transglutaminase (Tgm2), a multifunctional protein and established marker of M2 macrophages, is involved in acute and chronic graft rejection. We focus on leukocytes accumulating in blood vessels of rat renal allografts (Fischer-344 to Lewis), an established model for reversible acute rejection and CAI. Monocytes in graft blood vessels overexpress Tgm2 when acute rejection peaks on day 9 after transplantation. Concomitantly, caspase-3 is activated, suggesting that Tgm2 expression is linked to apoptosis. After resolution of acute rejection on day 42, leukocytic Tgm2 levels are lower and activated caspase-3 does not differ among isografts and allografts. Cystamine was applied for 4 weeks after transplantation to inhibit extracellular transglutaminase activity, which did, however, not reduce CAI in the long run. In conclusion, this is the first report on Tgm2 expression by monocytes in vivo. Tgm2 may be involved in leukocytic apoptosis and thus in reversion of acute rejection. However, our data do not support a role of extracellular transglutaminase activity as a factor triggering CAI during self-limiting acute rejection.

Rapidly Progressive Cardiac Allograft Vasculopathy in Early Onset Regressed With Everolimus Treatment in an Adult Cardiac Recipient

A 60-year-old man with severe heart failure underwent an orthotopic heart transplant. Maintenance immunosuppression consisted of a calcineurin inhibitor, mycophenolate mofetil (MMF), and a glucocorticoid. Six months after the transplantation, coronary angiography (CAG) and intravascular ultrasound sonography (IVUS) showed rapidly progressive cardiac allograft vasculopathy (CAV) along with acute cellular rejection. Methylprednisone pulse therapy resulted in the resolution of acute rejection. MMF was exchanged for everolimus (EVL) and 6 months after EVL therapy, CAG and IVUS revealed the regression of CAV. EVL can improve established CAV as well as prevent the progression of CAV.

Association of amino-terminal propeptide of type III procollagen and acute myocardial rejection in male patients receiving heart transplantation

The amino-terminal propeptides of type I and III procollagens (PINP and PIIINP) are markers reflecting the status of collagen turnover. We hypothesized that measurement of these serum procollagen propeptides could be used to non-invasively assess acute rejection in heart transplant recipients. In heart transplant recipients, endomyocardial biopsy specimens taken at 6 and 12 months after surgery were used for study. PINP and PIIINP were measured postoperatively at 3, 6, and 12 months. A total of 20 male heart transplant patients and seven male control subjects were enrolled. Five patients showed rejection 6 months after transplantation (group 1), while 15 patients showed no rejection (group 2). In group 2 patients, serum PINP and PIIINP levels decreased significantly 6 months after transplantation. In contrast, elevation of serum PINP and PIIINP levels persisted in group 1 patients 6 months after transplantation. At 6 months after transplantation, group 1 patients had significantly higher PIIINP levels than group 2 patients (p=0.025) and controls (p=0.003). After immunosuppressive therapy, all group 1 patients were free of rejection 12 months after transplantation and serial serum PIIINP levels decreased significantly in these patients. Serum PIIINP levels represent a non-invasive method to reflect the occurrence and resolution of acute rejection.

Persistent rejection of peritubular capillaries and tubules is associated with progressive interstitial fibrosis

We have reported that a 12-day course of high dose cyclosporine A treatment in thymectomized miniature swine with major histocompatibility complex (MHC) class I-mismatched renal allografts results in transient acute rejection followed by either in chronic rejection (progression group) or graft acceptance (recovery group). Here, we examined the differential features between both groups in the peritubular capillaries (PTCs) and tubules to clarify the pathogenesis of the progressive interstitial fibrosis in chronic rejection. Morphometric and immunohistochemical studies were performed on serial renal biopsies (days 0 to 100) obtained from both groups, focusing on the cellular infiltrate, rejection of PTCs and tubules, myofibroblast accumulation, and progressive interstitial fibrosis. In the progression group, acute rejection occurred by day 8 and progressed to chronic rejection by day 100, with the development of interstitial fibrosis. PTC endothelial cell and tubular epithelial cell death associated with CD3+ cell infiltration was evident, confirmed by nick end-labeling (TUNEL), commencing by day 8 and continuing thereafter. In acute rejection, destruction of PTCs and tubules accompanied by disruption of basement membrane (BM) occurred with capillaritis or tubulitis in areas with a severe cellular infiltrate. During the development of chronic rejection, capillaritis of PTCs and tubulitis continued by day 100, accompanied by persistent T cell infiltration, and the remaining PTCs and tubules exhibited progressive atrophy with thickening and/or lamination of BM. On day 100, identifiable PTCs and tubules were lost in areas of interstitial fibrosis. Proliferating (PCNA+) alpha-actin+ myofibroblasts accumulated around PTCs, tubules and in interstitium, and widespread interstitial fibrosis developed by day 100. In contrast, in the recovery group, injured PTCs and tubules recovered by day 100 based on the resolution of acute rejection, and minimal loss of PTCs and tubules was evident by day 100 with minimal interstitial fibrosis. Persistent rejection directed at PTCs and tubules, and proliferation of myofibroblasts are prominent features in the progressive interstitial fibrosis in chronic rejection, and are probably key events in its pathogenesis.

Phenotype, activation status, and suppressor activity of host lymphocytes during acute rejection and after cyclosporine-induced unresponsiveness of rat cardiac allografts.

Serial changes in phenotype, cell cycle, and functional behavior of lymphocyte subpopulations occurring both during acute rejection in unmodified hosts and in long-surviving heterotopic cardiac allografts in rats treated with cyclosporine (CsA) were studied. Using flow cytometry, RNA and DNA content of cells was examined during various phases of cell activation. In animals acutely rejecting their grafts, numbers of cells infiltrating the grafts and in host spleen in G1 phase (higher RNA content) increased, starting from day 3, and peaked by 5-6 days posttransplantation, and numbers of cells in S/G2/M phase (higher DNA content) remained stable. Similar, although slightly delayed changes were noted in CsA-treated recipients. The ratio of T helper (Th) to T suppressor/cytotoxic (Ts/c) phenotype cells infiltrating acutely rejecting grafts by day 3, was 1.6; it inverted abruptly to 0.7 by days 5-6, suggesting a preponderance of Ts/c during the later stages of allograft rejection. Ratio inversion occurred slightly later in host spleen and later in peripheral blood. Similarly, treatment with CsA produced a transient depression of Th, with recovery of the Th: Ts/c ratio during weeks 3-4 following transplantation. Adoptive transfer studies were then performed to investigate the functional significance of the T cell subsets. Survival of test grafts was prolonged significantly (ca. 14 days, P less than 0.001) when cells infiltrating grafts and spleen were transferred during inversion of Th:Ts/c; before that period, test graft survival was shortened in a second-set manner. These experiments suggest that suppressor cells may be responsible for resolution of acute rejection, as well as for host unresponsiveness seen after CsA treatment, and they represent an important homeostatic host mechanism following immunological stimulation.