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Kidney transplantation is the best option for kidney replacement therapy, even considering that most of the times the grafts do not survive as long as their recipients. In the Khalil et al's experience, published in this issue of the Journal, they analyze their second kidney graft survival and describe those significant predictors of early loss. This editorial comments on the results and put in perspec tive that most of the times, long-term graft survival could be inadvertently jeopardized if the immunosuppressive therapy is reduced or withdrawn for any reason, and that it could happen frequently if the transplant physician intends to innovate with the clinical care without proper evidence-based data.

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Objectives: Prophylactic acid suppression with proton pump inhibitors or H2 receptor antagonists is often administered after kidney transplantation. The Association of proton pump inhibitors or H2 receptor antagonists with acute rejection, hypomagnesemia, and graft loss in kidney transplant recipients is not well established. Material and Methods: We performed a retrospective cohort study of 302 kidney transplant recipients at one center (57% male; mean age 35.5±11.2 years) with more than 6 months post-transplant follow-up. Recipients were grouped according to gastric acid prophylaxis: only proton pump inhibitors (n=179), only H2 receptor antagonists (n=42), proton pump inhibitors and H2 receptor antagonists (n=55), and nonusers (n=26). The primary outcome was biopsy-proven acute rejection. Graft loss and hypomagnesemia were defined as secondary outcomes. Results: Nonusers were younger and mostly under steroid-free immunosuppression compared to other study groups (p=0.030 and p=0.009, respectively). The primary outcome was similar across study groups (p=0.266). Kaplan-Meier analyses also demonstrated similar 10-year graft survival rates: 95.5% for proton pump inhibitors, 97.6% for H2 receptor antagonists, 100% for proton pump inhibitors/H2 receptor antagonists, and 96.2% for nonusers (p=0.275). Conclusions: The use of proton pump inhibitors is not associated with acute rejection or graft loss but may cause mild hypomagnesemia in kidney transplant recipients.

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BACKGROUND: Acute rejection remains one of the main complications in the first months after transplantation and may influence long-term outcomes. Tacrolimus has proven its usefulness in solid organ transplants and its monitoring through the application of pharmacokinetic concepts to optimize individual drug therapy. OBJECTIVE: This research proposes to evaluate the tacrolimus pharmacokinetic parameters in patients suspected of acute kidney graft rejection under methylprednisolone pulse therapy. METHODS: Eleven adult tacrolimus-treated renal recipients were selected from a prospective, single-arm, single-center cohort study, with suspicion of acute rejection although in use of methylprednisolone pulses therapy. They were followed up for three months posttransplantation, being tacrolimus trough serum concentrations determined using a chemiluminescent magnetic immunoassay, and pharmacokinetic parameters were estimated by using a nonlinear mixed-effects model implemented by Monolix 2020R1. A tacrolimus trough serum concentration range of 8 to 12 ng.mL-1 was considered therapeutic. RESULTS: Six patients showed acute cellular rejection, and two of them in addition had an antibody- mediated rejection. Tacrolimus trough serum concentration was below the reference range in eight patients. Most patients showed a high tacrolimus concentration intrapatient and pharmacokinetic parameters variability. CONCLUSION: The obtained pharmacokinetics parameters helped in understanding the kidney recipient patients' tacrolimus behavior, assisting in the improvement of individual drug therapy and reducing the risk of acute rejection episodes.

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Intestinal transplantation (ITx) remains a lifesaving option for patients suffering from irreversible intestinal failure and complications from total parenteral nutrition. Since its inception, it became obvious that intestinal grafts are highly immunogenic, due to their high lymphoid load, the abundance in epithelial cells and constant exposure to external antigens and microbiota. This combination of factors and several redundant effector pathways makes ITx immunobiology unique. To this complex immunologic situation, which leads to the highest rate of rejection among solid organs (>40%), there is added the lack of reliable non-invasive biomarkers, which would allow for frequent, convenient and reliable rejection surveillance. Numerous assays, of which several were previously used in inflammatory bowel disease, have been tested after ITx, but none have shown sufficient sensibility and/or specificity to be used alone for diagnosing acute rejection. Herein, we review and integrate the mechanistic aspects of graft rejection with the current knowledge of ITx immunobiology and summarize the quest for a noninvasive biomarker of rejection.

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ABSTRACT Introduction: High uric acid levels are commonly encountered in kidney transplant recipients, and can be associated with allograft dysfunction. Our study aims to examine the relationship between UA levels and graft function in patients discontinuing steroids. Methods: In this single-center-retrospective study, 56 patients discontinued steroid therapy from among 678 RT patients transplanted from living donors between 1999-2020 were included. The mean age of the study group was 45.8±8.8 years. Causes of steroid discontinuation, creatinine levels concurrent with uric acid levels before and after steroid discontinuation (mean 3.9 ± 2.1 years), acute rejection numbers, demographics, durations of dialysis and transplantation, medications, laboratory data, human leukocyte antigen (HLA) mismatch numbers, blood-pressure (BP), body mass index, delayed acute rejection (DAR) numbers (3 months post-transplantation) were all recorded. Results: Creatinine and uric acid levels were seen to have increased after steroid discontinuation, there was a significant relationship between them (p<0.001). Statistically significant correlation was found between increased creatinine levels after steroid discontinuation and graft survival with higher HLA mismatch; 39 (69.6%) patients with mismatch ≥2, and 17 patients with mismatch <2 (30.4%) (p=0.049) . No significant relationship was found between DAR numbers before and after steroid discontinuation, and creatinine levels after steroid discontinuation. Conclusion: Per model obtained as a result of multivariate linear analysis, hyperuricemia and HLA mismatch numbers (p= 0.048 and p= 0.044, respectively) are independent predictive factors for graft dysfunction in patients discontinuing steroids. Accordingly, negative effects of modeling should be kept in mind for long-term graft survival in patients who plan to continue with steroid-sparing regimens.

RESUMEN Introducción: Con frecuencia se registran niveles elevados de ácido úrico en receptores de trasplantes renales que pueden estar asociados a disfunción de aloinjerto. El presente estudio tiene por objeto examinar la relación entre los niveles de AU y la función del injerto en pacientes que interrumpieron la terapia con esteroides. Métodos: En este estudio retrospectivo en un solo centro participaron 56 pacientes con interrupción de la terapia con esteroides de un total de 678 pacientes con TR receptores de trasplante de donantes vivos en el período 1999-2020. La edad promedio de la población de estudio fue de 45,8 ± 8,8 años. En el estudio se registraron causas de la interrupción de la terapia con esteroides, niveles de creatinina concurrentes con niveles de ácido úrico antes y después de la interrupción de la terapia con esteroides (promedio de 3,9 ± 2,1 años), números de rechazo agudo, datos demográficos, duraciones del período de diálisis y trasplante, medicación (uso de inmunosupresores, antihipertensivos), datos de laboratorio, números de desajuste del antígeno leucocitario humano (HLA), presión arterial (PA), índice de masa corporal, números de rechazo agudo retardado (DAR) (3 meses después del trasplante). Resultados: Se observó que los niveles de creatinina y ácido úrico aumentaron tras interrumpir la administración de esteroides, con una relación significativa entre ambos (p<0,001). Se identificó una correlación estadísticamente significativa entre el aumento en los niveles de creatinina tras la interrupción de la terapia de esteroides y la supervivencia del injerto con un mayor desajuste de HLA: 39 pacientes (el 69,6%) con desajuste ≥2 y 17 (el 30,4%) pacientes con desajuste <2 (p=0,049). No se encontró una relación significativa entre el número de DAR antes y después de la interrupción del tratamiento con esteroides, así como en los niveles de creatinina tras la interrupción de la terapia con esteroides. Conclusión: De acuerdo con el modelo obtenido como resultado del análisis lineal multivariable, la hiperuricemia y los números de desajuste de HLA (p=0,048 y p=0,044, respectivamente) constituyen factores predictivos independientes para la disfunción del injerto en pacientes que interrumpen la terapia con esteroides. En consecuencia, se deben tener en cuenta los efectos negativos del modelado para la supervivencia del injerto a largo plazo en pacientes que planean proseguir con regímenes con reducción de la administración esteroides.

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RATIONALE & OBJECTIVE: Donor acute kidney injury (AKI) activates innate immunity, enhances HLA expression in the kidney allograft, and provokes recipient alloimmune responses. We hypothesized that injury and inflammation that manifested in deceased-donor urine biomarkers would be associated with higher rates of biopsy-proven acute rejection (BPAR) and allograft failure after transplantation. STUDY DESIGN: Prospective cohort. SETTING & PARTICIPANTS: 862 deceased donors for 1,137 kidney recipients at 13 centers. EXPOSURES: We measured concentrations of interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) in deceased donor urine. We also used the Acute Kidney Injury Network (AKIN) criteria to assess donor clinical AKI. OUTCOMES: The primary outcome was a composite of BPAR and graft failure (not from death). A secondary outcome was the composite of BPAR, graft failure, and/or de novo donor-specific antibody (DSA). Outcomes were ascertained in the first posttransplant year. ANALYTICAL APPROACH: Multivariable Fine-Gray models with death as a competing risk. RESULTS: Mean recipient age was 54 ± 13 (SD) years, and 82% received antithymocyte globulin. We found no significant associations between donor urinary IL-18, KIM-1, and NGAL and the primary outcome (subdistribution hazard ratio [HR] for highest vs lowest tertile of 0.76 [95% CI, 0.45-1.28], 1.20 [95% CI, 0.69-2.07], and 1.14 [95% CI, 0.71-1.84], respectively). In secondary analyses, we detected no significant associations between clinically defined AKI and the primary outcome or between donor biomarkers and the composite outcome of BPAR, graft failure, and/or de novo DSA. LIMITATIONS: BPAR was ascertained through for-cause biopsies, not surveillance biopsies. CONCLUSIONS: In a large cohort of kidney recipients who almost all received induction with thymoglobulin, donor injury biomarkers were associated with neither graft failure and rejection nor a secondary outcome that included de novo DSA. These findings provide some reassurance that centers can successfully manage immunological complications using deceased-donor kidneys with AKI.

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The study aimed to investigate the impact of HLA-DPB1 allelic and molecular mismatches on the occurrence of acute rejection (AR) and low 5-year graft function (5Y-GF) in first kidney transplant (KT) recipients. This is a single center retrospective study of 130 deceased donor KT recipients transplanted between 2014 and 2016. HLA-DPB1 allelic MM and the following molecular MM (mMM) were analyzed: expression MM with the high expression G allele in the donor; T cell epitope MM (TCE MM); epitope MM (EMM), considering all six hypervariable regions (EMM-ABCDEF HVR), or only ABEF regions (EMM-ABEF HVR); eplet MM (EpMM); antibody-verified eplet MM (AbVer EpMM); and solvent accessible amino acid MM (SAMM). There was no association of allelic MM with AR or 5Y-GF. The variables independently associated (Cox regression analyses) with AR were high donor final creatinine, nonpermissive TCE MM, ABCDEF EMM load ≥6, EpMM load ≥6; SAMM load ≥5, and AbVer EpMM load ≥3. No association between any HLA-DPB1 mMM and 5Y-GF was observed when all 130 transplant recipients were considered. However, when transplants from expanded criteria donors were excluded, independent associations were detected (logistic regression analyses) with AbVerEpMM load ≥2, SAMM load ≥7, cerebro-vascular death, donor age, and AR. To our knowledge, this is the first study that shows that some HLA-DPB1 mMM are associated with AR and low 5Y-GF in a population of exclusively first kidney transplant recipients.

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Acute rejection (AR) is a process triggered via the recognition of grafted organ-derived antigens by the immune system, which could present as a life-threatening condition. In the context of a kidney transplant, despite improvement with immunosuppressive therapies, AR maintains a significant incidence of 10%, and currently available drugs generally act in similar and canonical pathways of lymphocyte activation. This prompted the research for different approaches to identify potential novel targets that could improve therapeutic interventions. Here, we conducted a transcriptome analysis comparing groups of acute rejection (including T cell-mediated rejection and antibody-mediated rejection) to stable grafts that included differentially expressed genes, transcription factor and kinase enrichment, and Gene Set Enrichment Analysis. These analyses revealed inflammasome enhancement in rejected grafts and AIM2 as a potential component linked to acute rejection, presenting a positive correlation to T-cell activation and a negative correlation to oxidative phosphorylation metabolism. Also, the AIM2 expression showed a global accuracy in discerning acute rejection grafts (area under the curve (AUC) = 0.755 and 0.894, p < 0.0001), and meta-analysis comprising different studies indicated a considerable enhancement of AIM2 in rejection (standardized mean difference (SMD) = 1.45, [CI 95%, 1.18 to 1.71]), especially for T cell-mediated rejection (TCMR) (SMD = 2.01, [CI 95%, 1.58 to 2.45]). These findings could guide future studies of AIM2 as either an adjuvant target for immunosuppression or a potential biomarker for acute rejection and graft survival.

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Delayed graft function (DGF) is a common complication of kidney transplantation and frequently leads to the necessity of surveillance biopsies. The purpose of this study is to describe the histological findings in surveillance biopsies of deceased donor kidney transplant recipients and evaluate the risk factors for graft outcomes. This is a monocentric, retrospective study including kidney transplant recipients that underwent a graft biopsy during the DGF period between January 2006 and July 2019. 356 biopsies were performed in 335 deceased donor transplant recipients. Biopsies were analyzed according to the Banff classification. The main histological findings were: acute tubular necrosis in 150 biopsies (42.1%), acute rejection in 96 biopsies (26.9%), and borderline findings in 91 biopsies (25.5%). In the multivariate analysis, recipient age (p = 0.028) and DGF duration (p = 0.005) were associated with rejection, antibody-induction with anti-thymocyte globulin (ATG) was protective (p = 0.001). The occurrence of rejection was associated with lower death-censored graft survival (log-rank; p = 0.009). Surveillance biopsies of kidney grafts experiencing DGF remain an essential tool for the care of kidney transplant recipients. The recipient's age and duration of DGF are independent risk factors for acute rejection, while antibody-induction therapy with ATG is associated with protection from its occurrence.

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