Low-affinity CD8+ T cells provide interclonal help to high-affinity CD8+ T cells to augment alloimmunity.

Following solid organ transplantation, small precursor populations of polyclonal CD8+ T cells specific for any graft-expressed antigen preferentially expand their high-affinity clones. This phenomenon, termed "avidity maturation," results in a larger population of CD8+ T cells with increased sensitivity to alloantigen, posing a greater risk for graft rejection. Using a mouse model of minor-mismatched skin transplantation, coupled with the tracking of 2 skin graft-reactive CD8+ T cell receptor-transgenic tracer populations with high and low affinity for the same peptide-major histocompatibility complex, we explored the conventional paradigm that CD8+ T cell avidity maturation occurs through T cell receptor affinity-based competition for cognate antigen. Our data revealed "interclonal CD8-CD8 help," whereby lower/intermediate affinity clones help drive the preferential expansion of their higher affinity counterparts in an interleukin-2/CD25-dependent manner. Consequently, the CD8-helped high-affinity clones exhibit greater expansion and develop augmented effector functions in the presence of their low-affinity counterparts, correlating with more severe graft damage. Finally, interclonal CD8-CD8 help was suppressed by costimulation blockade treatment. Thus, high-affinity CD8+ T cells can leverage help from low-affinity CD8+ T cells of identical specificity to promote graft rejection. Suppressing provision of interclonal CD8-CD8 help may be important to improve transplant outcomes.

Risk of cytomegalovirus infection and subsequent allograft failure after pancreas transplantation.

Cytomegalovirus (CMV) is a common cause of infection after transplantation, but few studies have evaluated its epidemiology, risk factors, and outcomes among pancreas transplant recipients. We performed a retrospective cohort study of adults who underwent pancreas transplantation from January 1, 2010, through December 31, 2020, at 3 sites in Arizona, Florida, and Minnesota. The primary outcome was clinically significant CMV infection (csCMVi), defined as CMV disease or infection requiring antiviral therapy. The secondary outcome was pancreas allograft failure. Among 471 pancreas transplant recipients, 117 (24.8%) developed csCMVi after a median of 226 (interquartile range 154-289) days. CMV donor (D)+/R- patients had a significantly higher incidence of csCMVi (hazard ratio [HR] 4.01, 95% confidence interval [CI] 2.10-7.64; P < .001). In adjusted analysis, a lower absolute lymphocyte count (ALC) was associated with a greater risk of csCMVi among seropositive recipients (HR 1.39 per 50% decrease, 95% CI 1.13-1.73; P = .002) but not among D+/R- patients (HR 1.04 per 50% decrease, 95% CI 0.89-1.23; P = .595). csCMVi, lower ALC, and acute rejection (P < .001) were independently associated with pancreas allograft failure. In conclusion, CMV D+/R- was associated with csCMVi in pancreas recipients, although ALC was associated with csCMVi only among seropositive patients. The development of csCMVi in pancreas recipients was associated with poor pancreas allograft outcomes.

Center variability in the prognostic value of a cumulative acute cellular rejection "A-score" for long-term lung transplant outcomes.

The acute rejection score (A-score) in lung transplant recipients, calculated as the average of acute cellular rejection A-grades across transbronchial biopsies, summarizes the cumulative burden of rejection over time. We assessed the association between A-score and transplant outcomes in 2 geographically distinct cohorts. The primary cohort included 772 double lung transplant recipients. The analysis was repeated in 300 patients from an independent comparison cohort. Time-dependent multivariable Cox models were constructed to evaluate the association between A-score and chronic lung allograft dysfunction or graft failure. Landmark analyses were performed with A-score calculated at 6 and 12 months posttransplant. In the primary cohort, no association was found between A-score and graft outcome. However, in the comparison cohort, time-dependent A-score was associated with chronic lung allograft dysfunction both as a time-dependent variable (hazard ratio, 1.51; P < .01) and when calculated at 6 months posttransplant (hazard ratio, 1.355; P = .031). The A-score can be a useful predictor of lung transplant outcomes in some settings but is not generalizable across all centers; its utility as a prognostication tool is therefore limited.

Clinical and molecular spectrum of v-lesion.

Isolated v-lesion presents diagnostic stratification and clinical challenges. We characterized allograft outcomes for this entity based on post-transplant time (early: ≤1 month vs. late: >1 month) and compared its molecular phenotype with other v+ rejection forms. Using the NanoString® B-HOT panel, we analyzed 92 archival FFPE kidney biopsies from three centers: isolated v-lesion (n=23), ABMR v+ (n=26), TCMR v+ (n=10), mixed rejection v+ (n=23), and normal tissue (n=10). Six gene sets (ABMR, DSAST, ENDAT, TCMR, early/acute injury, late injury) were assessed. Early isolated v-lesions had the poorest one-year death-censored graft survival compared to late isolated v-lesions or other rejections (p=0.034). Gene set analysis showed lower TCMR-related gene expression in isolated v+ groups than TCMR and mixed rejection (p<0.001). Both early and late isolated v-lesions had lower ABMR-related gene expression than ABMR, mixed rejection, and TCMR (p≤0.022). Late isolated v-lesions showed reduced DSAST and ENDAT gene expression versus ABMR (p≤0.046); and decreased early/acute injury gene expression than early isolated v+, ABMR, TCMR, and mixed rejection (p≤0.026). In conclusion, isolated v-lesions exhibit distinct gene expression patterns versus other rejection v+ forms. Early isolated v+ is associated with poorer prognosis and increased early/acute injury gene expression than late isolated v+, suggesting distinct etiologies.

Transcriptomics-based identification of TYROBP and TLR8 as novel macrophage-related biomarkers for the diagnosis of acute rejection after kidney transplantation.

Macrophages play an important role in the development and progression of acute rejection after kidney transplantation. The study aims to investigate the biological role and significance of macrophage-associated genes (MAG) in acute rejection after kidney transplantation. We utilized transcriptome sequencing results from public databases related to acute rejection of kidney transplantation for comprehensive analysis and validation in animal experiments. We found that a large number of immune-related signaling pathways are activated in acute rejection. PPI protein interaction networks and machine learning were used to establish a Hub gene consisting of TYROBP and TLR8 for the diagnosis of acute rejection. The single-gene GSEA enrichment analysis and immune cell correlation analysis revealed a close correlation between the expression of Hub genes and immune-related biological pathways as well as the expression of multiple immune cells. In addition, the study of TF, miRNAs, and drugs provided a theoretical basis for regulating and treating the Hub genes in acute rejection. Finally, the animal experiments demonstrated once again that acute rejection can aggravate kidney tissue damage, apoptosis level, and increase the release of inflammatory factors. We established and validated a macrophage-associated diagnostic model for acute rejection after kidney transplantation, which can accurately diagnose the biological alterations in acute rejection after kidney transplantation.

Automated Urinary Chemokine Assays for Noninvasive Detection of Kidney Transplant Rejection: A Prospective Cohort Study.

RATIONALE & OBJECTIVE: Prior studies have demonstrated the diagnostic potential of urinary chemokines C-X-C motif ligand 9 (CXCL9) and CXCL10 for kidney transplant rejection. However, their benefit in addition to clinical information has not been demonstrated. We evaluated the diagnostic performance for detecting acute rejection of urinary CXCL9 and CXCL10 when integrated with clinical information. STUDY DESIGN: Single-center prospective cohort study. SETTING & PARTICIPANTS: We analyzed 1,559 biopsy-paired urinary samples from 622 kidney transplants performed between April 2013 and July 2019 at a single transplant center in Belgium. External validation was performed in 986 biopsy-paired urinary samples. TESTS COMPARED: We quantified urinary CXCL9 (uCXCL9) and CXCL10 (uCXCL10) using an automated immunoassay platform and normalized the values to urinary creatinine. Urinary chemokines were incorporated into a multivariable model with routine clinical markers (estimated glomerular filtration rate, donor-specific antibodies, and polyoma viremia) (integrated model). This model was then compared with the tissue diagnosis according to the Banff classification for acute rejection. OUTCOME: Acute rejection detected on kidney biopsy using the Banff classification. RESULTS: Chemokines integrated with routine clinical markers had high diagnostic value for detection of acute rejection (n=150) (receiver operating characteristic area under the curve 81.3% [95% CI, 77.6-85.0]). The integrated model would help avoid 59 protocol biopsies per 100 patients when the risk for rejection is predicted to be below 10%. The performance of the integrated model was similar in the external validation cohort. LIMITATIONS: The cross-sectional nature obviates investigating the evolution over time and prediction of future rejection. CONCLUSIONS: The use of an integrated model of urinary chemokines and clinical markers for noninvasive monitoring of rejection could enable a reduction in the number of biopsies. Urinary chemokines may be useful noninvasive biomarkers whose use should be further studied in prospective randomized trials to clarify their role in guiding clinical care and the use of biopsies to detect rejection after kidney transplantation. PLAIN-LANGUAGE SUMMARY: Urinary chemokines CXCL9 and CXCL10 have been suggested to be good noninvasive biomarkers of kidney transplant rejection. However, defining a context of use and integration with clinical information is necessary before clinical implementation can begin. In this study, we demonstrated that urinary chemokines CXCL9 and CXCL10, together with clinical information, have substantial diagnostic accuracy for the detection of acute kidney transplant rejection. Application of urinary chemokines together with clinical information may guide biopsy practices following kidney transplantation and potentially reduce the need for kidney transplant biopsies.

Insights into IL-1 family cytokines in kidney allograft transplantation: IL-18BP and free IL-18 as emerging biomarkers.

Proinflammatory cytokines and their inhibitors are involved in the regulation of multiple immune reactions including response to transplanted organs. In this prospective study, we evaluated changes in serum concentrations of six IL-1 family cytokines (IL-1 alpha, IL-1 beta, IL-1RA, IL-18, IL-18BP, and IL-36 beta) in 138 kidney allograft recipients and 48 healthy donors. Samples were collected before transplantation and then after one week, three months and one year, additional sera were obtained at the day of biopsy positive for acute rejection. We have shown, that concentrations of proinflammatory members of the IL-1 family (IL-1ß, IL-18, IL-36 ß) and anti-inflammatory IL-18BP decreased immediately after the transplantation. The decline of serum IL-1RA and IL-1α was not observed in subjects with acute rejection. IL-18, including specifically its free form, is the only cytokine which increase serum concentrations in the period between one week and three months in both groups of patients without upregulation of its inhibitor, IL-18BP. Serum concentrations of calculated free IL-18 were upregulated in the acute rejection group at the time of acute rejection. We conclude that IL-1 family cytokines are involved mainly in early phases of the response to kidney allograft. Serum concentrations of free IL-18 and IL-18BP represent possible biomarkers of acute rejection, and targeting IL-18 might be of therapeutic value.

HLA matching between donors and recipients improves clinical liver transplant graft survival.

BACKGROUND AND AIMS: The importance of human leukocyte antigen (HLA) matching between liver transplant donors and recipients on graft survival remains unclear and is not a clinical consideration in liver transplantation. This study aimed to determine the relationship between HLA matching and liver graft survival using a large-scale multi-centre database (UNOS/OPTN) and multivariate logistic analysis. The secondary aim was to determine whether this relationship was influenced by transplant indication and donor status. METHODS: This retrospective observational analysis was performed using 22 702 liver transplant recipients from the UNOS/OPTN database. Patients were divided into two groups based on number of HLA mismatches (0-3 mismatches vs. 4-6 mismatches) and then subcategorized by indication and donor status. Risk-adjusted outcomes were assessed by multivariate Cox analysis adjusting for donor and recipient characteristics and visualized using Kaplan-Meier survival curves. RESULTS: Allograft survival and risk of acute rejection were associated with degree of HLA mismatch. This association between HLA mismatch and graft survival persisted in individuals who underwent transplant for hepatitis, metabolic, drug toxicity, and congenital indications. Donor status also influenced the relationship between HLA mismatch and graft survival. Graft survival in DBD recipients was longer than in DCD in the 4-6 HLA mismatch group, whereas no significant difference was found in the 0-3 HLA mismatch group. CONCLUSION: HLA mismatch significantly reduced graft survival and increased risk of acute rejection. This association was noted only in specific indications. These findings are of potential clinical relevance to organ allocation, allograft matching algorithms, immunosuppression protocols, and transplant surveillance.

Acute Rejection Rates in Vascularized Composite Allografts: A Systematic Review of Case Reports.

INTRODUCTION: Vascularized Composite Allografts (VCA) are usually performed in a full major histocompatibility complex mismatch setting, with a risk of acute rejection depending on factors such as the type of immunosuppression therapy and the quality of graft preservation. In this systematic review, we present the different immunosuppression protocols used in VCA and point out relationships between acute rejection rates and possible factors that might influence it. METHODS: This systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We systematically searched Medline (PubMed), Embase, and The Cochrane Library between November 2022 and February 2023, using following Mesh Terms: Transplant, Transplantation, Hand, Face, Uterus, Penis, Abdominal Wall, Larynx, and Composite Tissue Allografts. All VCA case reports and reviews describing multiple case reports were included. RESULTS: We discovered 211 VCA cases reported. The preferred treatment was a combination of antithymocyte globulins, mycophenolate mofetil (MMF), tacrolimus, and steroids; and a combination of MMF, tacrolimus, and steroids for induction and maintenance treatment, respectively. Burn patients showed a higher acute rejection rate (P = 0.073) and were administered higher MMF doses (P = 0.020). CONCLUSIONS: In contrast to previous statements, the field of VCA is not rapidly evolving, as it has encountered challenges in addressing immune-related concerns. This is highlighted by the absence of a standardized immunosuppression regimen. Consequently, more substantial data are required to draw more conclusive results regarding the immunogenicity of VCAs and the potential superiority of one immunosuppressive treatment over another. Future efforts should be made to report the VCA surgeries comprehensively, and muti-institutional long-term prospective follow-up studies should be performed to compare the number of acute rejections with influencing factors.

The impact of colonic allograft inclusion on intestinal transplantation outcomes: Results from UNOS/OPTN database analysis.

BACKGROUND: Outcomes of intestinal transplantation with colon allograft (ICTx) remain controversial. We aimed to assess the outcomes of ICTx in comparison to intestinal transplantation without colon (ITx) using the UNOS/OPTN registry database. METHODS: We retrospectively reviewed 2612 patients who received primary intestinal transplants from 1998 to 2020. The rates of acute rejection (AR) within 6 months after transplant were compared between ICTx and ITx. Risk factors of 6-month AR were examined using logistic regression model by era. Furthermore, conditional graft survival was analyzed to determine long-term outcomes of ICTx. RESULTS: Of 2612 recipients, 506 (19.4%) received ICTx. Graft and patient survival in ICTx recipients were comparable to those in ITx recipients. White ICTx recipients had a higher incidence of AR within 6 months compared to ITx during the entire study period (p = .002), colonic inclusion did not increase the risk of 6-month AR in the past decade. ICTx recipients who experienced 6-month AR had worse graft and patient survival compared to those who did not (p <.001 and p = .004, respectively). Among patients who did not develop 6-month AR, Cox proportional hazard model analysis revealed that colonic inclusion was independently associated with improved conditional graft survival. CONCLUSIONS: In the recent transplant era, colonic inclusion is no longer associated with a heightened risk of 6-month AR and may provide better long-term survival compared to ITx when AR is absent. Risk adjustment for rejection and proper immunosuppressive therapy are crucial to maximize the benefits of colonic inclusion.

Cannabis use is associated with reduced access to kidney transplantation and an increased risk of acute rejection post-transplant.

BACKGROUND: The association between cannabis use and access to waitlisting, transplantation, and post-transplant outcomes remains uncertain. METHODS: Patients referred for kidney transplant (KT) to the University Health Network from January 1, 2003, to June 30, 2020, and followed until December 31, 2020, were included. Predictors of reported cannabis use were examined using a logistic regression model. The association between cannabis use and time to clearance for KT, undergoing KT, and post-transplant outcomes was evaluated using Cox proportional hazards models. RESULTS: Among 3734 patients, the prevalence of reported cannabis use was 11.8%. Cannabis use was associated with a lower likelihood of KT clearance (adjusted hazard ratio [aHR] .82 [95% confidence interval (CI): .72, .94]). Once cleared for KT, cannabis use did not predict the subsequent receipt of KT (aHR .92, [95% CI: .79, 1.08]). Among 2091 KT recipients, cannabis use was associated with a higher likelihood of biopsy-proven acute rejection (aHR 1.55, [95% CI: 1.06, 2.27]). The relative hazard of death-censored graft failure was similarly elevated (aHR 1.60 [95% CI: .95, 2.72]). Cannabis use did not predict total graft failure (aHR 1.33 [95% CI: .90, 1.96]), death with graft function (aHR 1.06 [95% CI: .59, 1.89]), or hospital readmission in the first-year post-transplant (aHR 1.26 [95% CI: .95, 1.68]). CONCLUSIONS: Cannabis users have less access to transplantation and an increased risk of acute rejection, possibly leading to more graft loss. Further studies are warranted to understand possible mechanisms for the increased risk of allograft immune injury among cannabis users.

Outcomes of Deceased Donor Kidney Recipients From the Same Donor Based on Donor-Recipient Sex Discordance.

INTRODUCTION: Outcomes of deceased donor kidney transplant (DDKT) recipients from the same donor with donor-recipient sex discordance have been studied with inconsistent results. METHODS: Adult DDKT where both kidneys from the same donor occurred at our center in two different recipients of different sexes were included. Outcomes were analyzed separately for male and female donors, based on the concordance or discordance between donor-recipient sex: Male-male (M-m) versus Male to female (M-f) or vice versa, F-f versus F-m. Acute rejection (AR) and uncensored graft failure were primary outcomes of interest. The univariate and multivariate risks for AR and graft failure were conducted using the Cox proportional hazards model and log-rank tests. RESULTS: A total of 130 donors, 84 male and 46 female fulfilled our selection criteria and were transplanted in 260 recipients. With respect to the concordant groups (M-m or F-f), sex discordance was not significantly associated with the risk of rejection in multivariate analysis (M-f vs. M-m HR 1.15 [0.53-2.53, P = 0.72]; F-m vs. F-f HR 1.77 [0.71-4.39, P = 0.23]). Sex discordance was also not significantly associated with graft failure in multivariate analysis. Interestingly, risk factors for AR differed among male donors and female donors. The higher calculated panel reactive antibodies (cPRA) and nonwhite recipients were at increased risk for AR in F-m, but not in M-f. CONCLUSIONS: Donor-recipient sex discordance was not significantly associated with AR or graft failure. Risk factors for AR may differ across male and female donors.

Association of BKV viremia and nephropathy with adverse alloimmune outcomes in kidney transplant recipients.

BACKGROUND: Immunosuppression reduction for BK polyoma virus (BKV) must be balanced against risk of adverse alloimmune outcomes. We sought to characterize risk of alloimmune events after BKV within context of HLA-DR/DQ molecular mismatch (mMM) risk score. METHODS: This single-center study evaluated 460 kidney transplant patients on tacrolimus-mycophenolate-prednisone from 2010-2021. BKV status was classified at 6-months post-transplant as "BKV" or "no BKV" in landmark analysis. Primary outcome was T-cell mediated rejection (TCMR). Secondary outcomes included all-cause graft failure (ACGF), death-censored graft failure (DCGF), de novo donor specific antibody (dnDSA), and antibody-mediated rejection (ABMR). Predictors of outcomes were assessed in Cox proportional hazards models including BKV status and alloimmune risk defined by recipient age and molecular mismatch (RAMM) groups. RESULTS: At 6-months post-transplant, 72 patients had BKV and 388 had no BKV. TCMR occurred in 86 recipients, including 27.8% with BKV and 17% with no BKV (p = .05). TCMR risk was increased in recipients with BKV (HR 1.90, (95% CI 1.14, 3.17); p = .01) and high vs. low-risk RAMM group risk (HR 2.26 (95% CI 1.02, 4.98); p = .02) in multivariable analyses; but not HLA serological MM in sensitivity analysis. Recipients with BKV experienced increased dnDSA in univariable analysis, and there was no association with ABMR, DCGF, or ACGF. CONCLUSIONS: Recipients with BKV had increased risk of TCMR independent of induction immunosuppression and conventional alloimmune risk measures. Recipients with high-risk RAMM experienced increased TCMR risk. Future studies on optimizing immunosuppression for BKV should explore nuanced risk stratification and may consider novel measures of alloimmune risk.

Alemtuzumab induction is associated with decreased hospitalization rates in pediatric kidney transplant: A UNOS data review for safety and outcomes with common induction regimens.

BACKGROUND: We hypothesized that alemtuzumab use is safe in pediatric kidney transplant recipients (KTRs) with equivalent long-term outcomes compared to other induction agents. METHODS: Using pediatric kidney transplant recipient data in the UNOS database between January 1, 2000, and June 30, 2022, multivariate logistic regression, multivariable Cox regression, and survival analyses were utilized to estimate the likelihoods of 1st-year and all-time hospitalizations, acute rejection, CMV infection, delayed graft function (DGF), graft loss, and patient mortality among recipients of three common induction regimens (ATG, alemtuzumab, and basiliximab). RESULTS: There were no differences in acute rejection or graft failure among induction or maintenance regimens. Basiliximab was associated with lower odds of DGF in deceased donor recipients (OR 0.77 [0.60-0.99], p = .04). Mortality was increased in patients treated with steroid-containing maintenance (HR 1.3 [1.005-1.7] p = .045). Alemtuzumab induction correlated with less risk of CMV infection than ATG (OR 0.76 [0.59-0.99], p = .039). Steroid-containing maintenance conferred lower rate of PTLD compared to steroid-free maintenance (HR 0.59 [0.4-0.8] p = .001). Alemtuzumab was associated with less risk of hospitalization within 1 year (OR 0.79 [0.67-0.95] p = .012) and 5 years (HR 0.54 [0.46-0.65] p < .001) of transplantation. Steroid maintenance also decreased 5 years hospitalization risk (HR 0.78 [0.69-0.89] p < .001). CONCLUSIONS: Pediatric KTRs may be safely treated with alemtuzumab induction without increased risk of acute rejection, DGF, graft loss, or patient mortality. The decreased risk of CMV infections and lower hospitalization rates compared to other agents make alemtuzumab an attractive choice for induction in pediatric KTRs, especially in those who cannot tolerate ATG.

Utilization of donor-derived Cell-Free DNA in pediatric kidney transplant recipients: A single center study.

High donor-derived cell-free DNA (dd-cfDNA) levels indicate transplant allograft injury and can identify graft rejection in kidney transplant recipients. Here, we evaluated the use of dd-cfDNA in pediatric kidney transplant rejection monitoring and treatment. METHODS: Forty-two pediatric kidney transplant patients were enrolled between February 2020 and August 2021. Dd-cfDNA was tested before and after biopsy/rejection treatment. There was a total of 61 allograft biopsies (44 for-cause, 17 surveillance). RESULTS: Graft rejection was found in 35/61 biopsies. Rejection was more common in basiliximab induction compared to rATG (77.1% vs. 22.9%, p = .0121). Median dd-cfDNA was higher in those with rejection (1.2% [0.34-3.12] vs. 0.24% [0.08-0.78], p < .0001). Dd-cfDNA was highest in biopsies with AMR and mixed AMR/TCMR. In addition, dd-cfDNA in basiliximab induction was higher compared to rATG (0.92% [0.27-1.8] vs. 0.26% [0.08-2], p = .0437). Median change in dd-cfDNA after rejection treatment was -0.57% (-1.67 to 0.05). Median time to dd-cfDNA <1% post-rejection treatment was 8.5 days (3.0-19.5). Dd-cfDNA in AMR was higher compared to TCMR or mixed rejection, and levels remained higher in AMR after treatment. In surveillance biopsies, 4/17 had rejection. Median dd-cfDNA was not different in those with versus without rejection (0.48% vs. 0.28%, p = .2342). Those without rejection all had dd-cfDNA <1%. In those with rejection, only one patient had dd-cfDNA >1%, and all had TCMR. CONCLUSIONS: Our findings support dd-cfDNA as a useful indicator of graft rejection and response to treatment. Additional studies are needed to determine the role of dd-cfDNA in graft health surveillance.

Evaluating threshold for donor fraction cell-free DNA using clinically available assay for rejection in pediatric and adult heart transplantation.

BACKGROUND: The aims of the study were to assess the performance of a clinically available cell-free DNA (cfDNA) assay in a large cohort of pediatric and adult heart transplant recipients and to evaluate performance at specific cut points in detection of rejection. METHODS: Observational, non-interventional, prospective study enrolled pediatric and adult heart transplant recipients from seven centers. Biopsy-associated plasma samples were used for cfDNA measurements. Pre-determined cut points were tested for analytic performance. RESULTS: A total of 487 samples from 160 subjects were used for the analysis. There were significant differences for df-cfDNA values between rejection [0.21% (IQR 0.12-0.69)] and healthy samples [0.05% (IQR 0.01-0.14), p < .0001]. The pediatric rejection group had a median df-cfDNA value of 0.93% (IQR 0.28-2.84) compared to 0.09% (IQR 0.04-0.23) for healthy samples, p = .005. Overall negative predictive value was 0.94 while it was 0.99 for pediatric patients. Cut points of 0.13% and 0.15% were tested for various types of rejection profiles and were appropriate to rule out rejection. CONCLUSION: The study suggests that pediatric patients with rejection show higher levels of circulating df-cfDNA compared to adults and supports the specific cut points for clinical use in pediatric and adult patients with overall acceptable performance.

Functional MRI evaluation of blood oxygen dependent (BOLD) in renal allograft dysfunction: a prospective study.

BACKGROUND: Blood oxygen level dependent-magnetic resonance imaging (BOLD-MRI) is a non-invasive functional imaging technique that can be used to assess renal allograft dysfunction. PURPOSE: To evaluate the diagnostic performance of BOLD-MRI using a 3-T scanner in discriminating causes of renal allograft dysfunction in the post-transplant period. MATERIAL AND METHODS: This prospective study was conducted on 112 live donor-renal allograft recipients: 53 with normal graft function, as controls; 18 with biopsy-proven acute rejection (AR); and 41 with biopsy-proven acute tubular necrosis (ATN). Multiple fast-field echo sequences were performed to obtain T2*-weighted images. Cortical R2* (CR2*) level, medullary R2* (MR2*) level, and medullary over cortical R2* ratio (MCR) were measured in all participants. RESULTS: The mean MR2* level was significantly lower in the AR group (20.8 ± 2.8/s) compared to the normal group (24 ± 2.4/s, P <0.001) and ATN group (27.4 ± 1.7/s, P <0.001). The MCR was higher in ATN group (1.47 ± 0.18) compared to the AR group (1.18 ± 0.17) and normal functioning group (1.34 ± 0.2). Both MR2* (area under the curve [AUC] = 0.837, P <0.001) and MCR (AUC = 0.727, P = 0.003) can accurately discriminate ATN from AR, however CR2* (AUC = 0.590, P = 0.237) showed no significant difference between both groups. CONCLUSION: In early post-transplant renal dysfunction, BOLD-MRI is a valuable non-invasive diagnostic technique that can differentiate between AR and ATN by measuring changes in intra-renal tissue oxygenation.

Salidroside ameliorates acute liver transplantation rejection in rats by inhibiting neutrophil extracellular trap formation.

Acute rejection is an important factor affecting the survival of recipients after liver transplantation. Salidroside has various properties, including anti-inflammatory, antioxidant, and hepatoprotective properties. This study aims to investigate whether salidroside can prevent acute rejection after liver transplantation and to examine the underlying mechanisms involved. An in vivo acute rejection model is established in rats that are pretreated with tacrolimus (1 mg/kg/d) or salidroside (10 or 20 mg/kg/d) for seven days after liver transplantation. In addition, an in vitro experiment is performed using neutrophils incubated with salidroside (1, 10, 50 or 100 µM). Hematoxylin-eosin staining, terminal deoxynucleotidyl transferase dUTP nick-end labeling staining, immunosorbent assays, immunofluorescence analysis, Evans blue staining, and western blot analysis are performed to examine the impact of salidroside on NET formation and acute rejection in vitro and in vivo. We find that Salidroside treatment reduces pathological liver damage, serum aminotransferase level, and serum levels of IL-1ß, IL-6, and TNF-α in vivo. The expressions of proteins associated with the HMGB1/TLR-4/MAPK signaling pathway (HMGB1, TLR-4, p-ERK1/2, p-JNK, p-P38, cleaved caspase-3, cleaved caspase-9, Bcl-2, Bax, IL-1ß, TNF-α, and IL-6) are also decreased after salidroside treatment. In vitro experiments show that the release of HMGB1/TLR-4/MAPK signaling pathway-associated proteins from neutrophils treated with lipopolysaccharide is decreased by salidroside. Moreover, salidroside inhibits NETosis and protects against acute rejection by regulating the HMGB1/TLR-4/MAPK signaling pathway. Furthermore, salidroside combined with tacrolimus has a better effect than either of the other treatments alone. In summary, salidroside can prevent acute liver rejection after liver transplantation by reducing neutrophil extracellular trap development through the HMGB1/TLR-4/MAPK signaling pathway.

Transitional B cell cytokines risk stratify early borderline rejection after renal transplantation.

Borderline rejection (BL) in renal transplantation is associated with decreased allograft survival, yet many patients with BL maintain stable graft function. Identifying patients with early BL at risk for shortened allograft survival would allow for timely targeted therapeutic intervention aimed at improving outcomes. 851/1187 patients transplanted between 2013-18 underwent early biopsy (0-4 mos). 217/851 (25%) had BL and were compared to 387/851 without significant inflammation (NI). Serial surveillance and for-cause biopsies and seven-year follow-up were used to evaluate histological and clinical progression. To identify high-risk patients, we examined clinical/histological parameters using regression and non-linear dimensionality reduction (tSNE) and a biomarker based on peripheral blood transitional-1 B cell (T1B) IL-10/TNFα ratio. Compared to NI, early BL was associated with increased progression to late acute rejection (AR; 5-12 mos), premature interstitial fibrosis and tubular atrophy (IFTA) and decreased seven-year graft survival. However, decreased graft survival was limited to BL patients who progressed to late AR or IFTA, and was not influenced by treatment. Although tSNE clustered patients into groups based on clinical factors, the ability of these factors to risk stratify BL patients was modest. In contrast, a low T1B IL-10/TNFα ratio at 3 months identified BL patients at high risk for progression to AR (ROC AUC 0.87) and poor 7-yr graft survival (52% vs. 92%, p=0.003), while BL patients with a high ratio had similar graft survival to patients with NI (91%, p=NS). Thus, progressive early allograft inflammation manifested as BL that progresses to late AR in the first post-transplant year represents a high-risk clinical state for poor allograft outcomes. Such high-risk status can be predicted by the T1B IL-10/TNFα ratio before irreversible scarring sets in, thus allowing timely risk stratification.

miR-449a ameliorates acute rejection after liver transplantation via targeting procollagen-lysine1,2-oxoglutarate5-dioxygenase 1 in macrophages.

Acute rejection (AR) is an important factor that leads to poor prognosis after liver transplantation (LT). Macrophage M1-polarization is an important mechanism in AR development. MicroRNAs play vital roles in disease regulation; however, their effects on macrophages and AR remain unclear. In this study, rat models of AR were established following LT, and macrophages and peripheral blood mononuclear cells were isolated from rats and humans, respectively. We found miR-449a expression to be significantly reduced in macrophages and peripheral blood mononuclear cells. Overexpression of miR-449a not only inhibited the M1-polarization of macrophages in vitro but also improved the AR of transplant in vivo. The mechanism involved inhibiting the noncanonical nuclear factor-kappaB (NF-κB) pathway. We identified procollagen-lysine1,2-oxoglutarate5-dioxygenase 1 (PLOD1) as a target gene of miR-449a, which could reverse miR-449a's inhibition of macrophage M1-polarization, amelioration of AR, and inhibition of the NF-κB pathway. Overall, miR-449a inhibited the NF-κB pathway in macrophages through PLOD1 and also inhibited the M1-polarization of macrophages, thus attenuating AR after LT. In conclusion, miR-449a and PLOD1 may be new targets for the prevention and mitigation of AR.