The Impact of Early Clinical and Subclinical T Cell-mediated Rejection After Kidney Transplantation

Evolution of human kidney allograft pathology diagnostics through 30 years of the Banff classification process

The second half of the previous century witnessed a tremendous rise in the number of clinical kidney transplants worldwide. This activity was, however, accompanied by many issues and challenges. An accurate diagnosis and appropriate management of causes of graft dysfunction were and still are, a big challenge. Kidney allograft biopsy played a vital role in addressing the above challenge. However, its interpretation was not standardized for many years until, in 1991, the Banff process was started to fill this void. Thereafter, regular Banff meetings took place every 2 years for the past 30 years. Marked changes have taken place in the interpretation of kidney allograft biopsies, diagnosis, and classification of rejection and other non-rejection pathologies from the original Banff 93 classification. This review attempts to summarize those changes for increasing the awareness and understanding of kidney allograft pathology through the eyes of the Banff process. It will interest the transplant surgeons, physicians, pathologists, and allied professionals associated with the care of kidney transplant patients.

The Clinical Utility of Post-Transplant Monitoring of Donor-Specific Antibodies in Stable Renal Transplant Recipients: A Consensus Report With Guideline Statements for Clinical Practice

Solid phase immunoassays improved the detection and determination of the antigen-specificity of donor-specific antibodies (DSA) to human leukocyte antigens (HLA). The widespread use of SPI in kidney transplantation also introduced new clinical dilemmas, such as whether patients should be monitored for DSA pre- or post-transplantation. Pretransplant screening through SPI has become standard practice and DSA are readily determined in case of suspected rejection. However, DSA monitoring in recipients with stable graft function has not been universally established as standard of care. This may be related to uncertainty regarding the clinical utility of DSA monitoring as a screening tool. This consensus report aims to appraise the clinical utility of DSA monitoring in recipients without overt signs of graft dysfunction, using the Wilson & Junger criteria for assessing the validity of a screening practice. To assess the evidence on DSA monitoring, the European Society for Organ Transplantation (ESOT) convened a dedicated workgroup, comprised of experts in transplantation nephrology and immunology, to review relevant literature. Guidelines and statements were developed during a consensus conference by Delphi methodology that took place in person in November 2022 in Prague. The findings and recommendations of the workgroup on subclinical DSA monitoring are presented in this article.

The Association Between Kidney Donor Profile Index and 1-y Graft Function

The association between Kidney Donor Profile Index (KDPI) and 1-y estimated glomerular filtration rate (eGFR) with long-term kidney graft survival is well known. Yet, the association between KDPI and 1-y eGFR remains uncertain considering the several concurrent competing risk factors.

Methods

This single-center, retrospective cohort study analyzed data from 3059 consecutive deceased donor kidney transplant recipients with a 1-y follow-up from January 2013 to December 2017. The aim was to determine the association between the KDPI strata (0%-35%, 36%-50%, 51%-85%, 86%-100%) and 1-y eGFR estimated by the CKD-EPI equation.

Results

The incidence of delayed graft function (50.6% versus 59.3% versus 62.7% versus 62.0%; P < 0.001) and cytomegalovirus infection (36.7% versus 36.6% versus 43.3% versus 57.8%; P < 0.001) increased with increasing KDPI strata but not biopsy-proven acute rejection (9.1% versus 9.8% versus 8.4% versus 9.1%; P = 0.736). The median 1-y eGFR decreased with increasing KDPI strata (64.8 versus 53.5 versus 46.9 versus 39.1 mL/min/1.73 m²; P < 0.001). In the Cox regression, the higher the KDPI was, the lower the probability of a lower 1-y eGFR was. Assuming the 0%-35% strata as the reference, the likelihood of eGFR <50 mL/min/1.73 m² was increased by 76.6% (hazard ratio [HR] = 1.767, 95% confidence interval [CI] = 1.406-2.220), 2.24- and 2.87-fold higher for KDPI higher >35%-50% (HR = 2.239, 95% CI = 1.862-2.691), and >51%-85% (HR = 2.871, 95% CI = 2.361-3.491), respectively. Other variables associated with a lower graft function were donor sex (HR male versus female = 0.896, 95% CI = 0.813-0.989) and cold ischemia time (HR for each hour = 1.011, 95% CI = 1.004-1.019). This association was sustained after the Poisson mediation analysis, including delayed graft function, cytomegalovirus, and acute rejection as mediators.

Conclusions

In this cohort of deceased donor kidney recipients, KDPI, and cold ischemia time were the major independent risk factors associated with lower 1-y kidney function.

Function and longevity of renal grafts from high-KDPI donors

BACKGROUND

High kidney-donor profile index (KDPI) kidneys have a shorter survival than grafts with lower KDPI values. It is still unclear, however, whether their shorter longevity depends on an inferior baseline function, faster functional decline, or the combination of both.

METHODS

We analyzed the estimated glomerular filtration rate (eGFR) of 605 consecutive recipients of deceased donor kidney transplants (KT) at 1, 3, 6, 12, 18, 24, 36, 48, and 60 months. Comparisons were performed among four groups based on KDPI quartile: Group I-KDPI ≤ 25% (n = 151), Group II-KDPI 26-50% (n = 182), Group III-KDPI 51-75% (n = 176), and Group IV-KDPI 〉 75% (n = 96). Linear mixed model analysis was subsequently used to assess whether KDPI was independently associated with the decline in eGFR during the first 5-years after KT. We also analyzed the incidence of delayed graft function (DGF), rejection within the first year after KT, patient survival, graft survival, and death censored graft survival based on KDPI group.

FINDINGS

High-KDPI grafts had lower eGFR immediately after KT, had a higher incidence of DGF and rejection. However, there were no signifcant differences in the adjusted rate (slope) of decline in eGFR among the four KDPI groups (P = .06). Although patient survival was signigicantly lower for recipients of high-KDPI grafts, death-censored graft survival was similar among the four KDPI groups (P = .33).

CONCLUSIONS

The shorter functional survival of high-KDPI grafts seems to be due to their lower baseline eGFR rather than a more rapid functional decline after KT.

The negative impact of T cell-mediated rejection on renal allograft survival in the modern era

The prevalence and long-term impact of T cell-mediated rejection (TCMR) is poorly defined in the modern era of tacrolimus/mycophenolate-based maintenance therapy. This observational study evaluated 775 kidney transplant recipients with serial histology and correlated TCMR events with the risk of graft loss. After a ~30% incidence of a first Banff Borderline or greater TCMR detected on for-cause (17%) or surveillance (13%) biopsies, persistent (37.4%) or subsequent (26.3%) TCMR occurred in 64% of recipients on follow-up biopsies. Alloimmune risk categories based on the HLA-DR/DQ single molecule eplet molecular mismatch correlated with the number of TCMR events (p = .002) and Banff TCMR grade (p = .007). Both a first and second TCMR event correlated with death-censored and all-cause graft loss when adjusted for baseline covariates and other significant time-dependent covariates such as DGF and ABMR. Therefore, a substantial portion of kidney transplant recipients, especially those with intermediate and high HLA-DR/DQ molecular mismatch scores, remain under-immunosuppressed, which in turn identifies the need for novel agents that can more effectively prevent or treat TCMR.

Effectiveness of T cell-mediated rejection therapy: A systematic review and meta-analysis

The effectiveness of T cell-mediated rejection (TCMR) therapy for achieving histological remission remains undefined in patients on modern immunosuppression. We systematically identified, critically appraised, and summarized the incidence and histological outcomes after TCMR treatment in patients on tacrolimus (Tac) and mycophenolic acid (MPA). English-language publications were searched in MEDLINE (Ovid), Embase (Ovid), Cochrane Central (Ovid), CINAHL (EBSCO), and Clinicaltrials.gov (NLM) up to January 2021. Study quality was assessed with the National Institutes of Health Study Quality Tool. We pooled results using an inverse variance, random-effects model and report the binomial proportions with associated 95% confidence intervals (95% CI). Statistical heterogeneity was explored using the I²  statistic. From 2875 screened citations, we included 12 studies (1255 participants). Fifty-eight percent were good/high quality while the rest were moderate quality. Thirty-nine percent of patients (95% CI 0.26-0.53, I² 77%) had persistent ≥Banff Borderline TCMR 2-9 months after anti-rejection therapy. Pulse steroids and augmented maintenance immunosuppression were mainstays of therapy, but considerable practice heterogeneity was present. A high proportion of biopsy-proven rejection exists after treatment emphasizing the importance of histology to characterize remission. Anti-rejection therapy is foundational to transplant management but well-designed clinical trials in patients on Tac/MPA immunosuppression are lacking to define the optimal therapeutic approach.

Donor-derived Cell-free DNA in Solid-organ Transplant Diagnostics: Indications, Limitations, and Future Directions

The last few years have seen an explosion in clinical research focusing on the use of donor-derived cell-free DNA (dd-cfDNA) in solid-organ transplants (SOT). Although most of the literature published so far focuses on kidney transplants, there are several recent as well as ongoing research studies on heart, lung, pancreas, and liver transplants. Though initially studied as a noninvasive means of identifying subclinical or acute rejection in SOT, it is rapidly becoming clear that instead of being a specific marker for allograft rejection, dd-cfDNA is more appropriately described as a marker of severe injury, although the most common cause of this injury is allograft rejection. Multiple studies in kidney transplants have shown that although sensitivity for the diagnosis of antibody-mediated rejection is excellent, it is less so for T-cell-mediated rejection. It is possible that combining dd-cfDNA with other novel urine- or blood-based biomarkers may increase the sensitivity for the diagnosis of rejection. Irrespective of the cause, though, elevated dd-cfDNA seems to portend adverse allograft prognosis and formation of de novo donor-specific antibody. Although current data do not lend themselves to a clear conclusion, ongoing studies may reveal the utility of serial surveillance for the management of SOT as following levels of dd-cfDNA over time may provide windows of opportunity to intervene early and before irreversible allograft injury. Finally, cost-effectiveness studies will be needed to guide the ideal incorporation of dd-cfDNA into routine clinical practice.

Advantages of plasmatic CXCL-10 as a prognostic and diagnostic biomarker for the risk of rejection and subclinical rejection in kidney transplantation

This study evaluate the potential of plasmatic CXCL-10 (pCXCL-10) as a pre&post transplantation prognostic and diagnostic biomarker of T-cell-mediated rejection (TCMR), antibody-mediated rejection (ABMR) and subclinical rejection (SCR) risk in adult kidney recipients considering BKV and CMV infections as possible clinical confounder factors. Twenty-eight of 100 patients included experienced rejection (TCMR:14; ABMR:14); 8 SCR; 13 and 16 were diagnosed with BKV and CMV infection, respectively. Pre-transplantation pCXCL-10 was significantly increased in TCMR and ABMR and post-transplantation in TCMR, ABMR and SCR compared with nonrejectors. All CMV⁺ patients showed pCXCL-10 levels above the cutoff values established for rejection whereas the 80% of BKV⁺ patients showed pCXCL-10 concentration < 100 pg/mL. pCXCL-10 could improve pre-transplantation patient stratification and immunosuppressive treatment selection according to rejection risk; and after kidney transplantation could be a potential early prognostic biomarker for rejection. Clinical confounding factor in BKV⁺ and particularly in CMV⁺ patients must be discarded.

Impact of Subclinical and Clinical Kidney Allograft Rejection Within 1 Year Posttransplantation Among Compatible Transplant With Steroid Withdrawal Protocol

Early acute kidney rejection remains an important clinical issue.

Methods

The current study included 552 recipients who had 1-2 surveillance or indication biopsy within the 1 y posttransplant. We evaluated the impact of type of allograft inflammation on allograft outcome. They were divided into 5 groups: no inflammation (NI: 95), subclinical inflammation (SCI: 244), subclinical T cell-mediated rejection (TCMR) (SC-TCMR: 110), clinical TCMR (C-TCMR: 83), and antibody-mediated rejection (AMR: 20). Estimated glomerular filtration rate (eGFR) over time using linear mixed model, cumulative chronic allograft scores/interstitial fibrosis and tubular atrophy (IFTA) ≥2 at 12 mo, and survival estimates were compared between groups.

Results

The common types of rejections were C-TCMR (15%), SC-TCMR (19.9%), and AMR (3.6%) of patients. Eighteen of 20 patients with AMR had mixed rejection with TCMR. Key findings were as follows: (i) posttransplant renal function: eGFR was lower for patients with C-TCMR and AMR (P < 0.0001) compared with NI, SCI, and SC-TCMR groups. There was an increase in delta-creatinine from 3 to 12 mo and cumulative allograft chronicity scores at 12 mo (P < 0.001) according to the type of allograft inflammation. (ii) Allograft histology: the odds of IFTA ≥2 was higher for SC-TCMR (3.7 [1.3-10.4]; P = 0.04) but was not significant for C-TCMR (3.1 [1.0-9.4]; P = 0.26), and AMR (2.5 [0.5-12.8]; P = 0.84) compared with NI group, and (iii) graft loss: C-TCMR accounted for the largest number of graft losses and impending graft losses on long-term follow-up. Graft loss among patient with AMR was numerically higher but was not statistically significant.

Conclusions

The type of kidney allograft inflammation predicted posttransplant eGFR, cumulative chronic allograft score/IFTA ≥2 at 12 mo, and graft loss.

Correlation of Donor-Derived Cell-free DNA with Histology and Molecular Diagnoses of Kidney Transplant Biopsies

BACKGROUND

Circulating donor-derived cell free DNA (cfDNA), a minimally invasive diagnostic tool for kidney transplant rejection, was validated using traditional histology. The Molecular Microscope (MMDx) tissue gene expression platform may provide increased precision to traditional histology.

METHODS

In this single-center prospective study of 208 biopsies (median=5.8 months) post-transplant, we report on the calibration of cfDNA with simultaneous biopsy assessments using MMDx and histology by Area under the curve (AUC) analyses for optimal criterion, as well as for, previously published cfDNA cut-offs ≤0.21% to 'rule-out' rejection and ≥1% to 'rule-in' rejection.

RESULTS

There were significant discrepancies between histology and MMDx, with MMDx identifying more antibody-mediated rejection (65; 31%) than histology (43; 21%); the opposite was true for T-cell mediated rejection [TCMR; histology: 27 (13%) vs MMDx: 13 (6%)]. Most of the TCMR discrepancies were seen for histologic borderline/1A TCMR. AUC Curves for cfDNA and prediction of rejection were slightly better with MMDx (AUC=0.80; 95%CI: 0.74-0.86) vs. histology (AUC=0.75; 95%CI: 0.69-0.81). A cfDNA≤0.21% had similar sensitivity (~91%) to 'rule-out' rejection by histology and MMDx. Specificity was slightly higher with MMDx (92%) compared with histology (85%) to 'rule-in' rejection using cfDNA criterion≥1%. Strong positive quantitative correlations were observed between cfDNA scores and molecular acute kidney injury (AKI) for both 'rejection' and 'nonrejection' biopsies.

CONCLUSIONS

Molecular diagnostics using tissue gene expression and blood-based donor-derived cell-free DNA may add precision to some cases of traditional histology. The positive correlation of cfDNA with molecular AKI suggests a dose-dependent association with tissue injury irrespective of rejection characteristics.

Clinical Relevance of Corticosteroid Withdrawal on Graft Histological Lesions in Low-Immunological-Risk Kidney Transplant Patients

The impact of corticosteroid withdrawal on medium-term graft histological changes in kidney transplant (KT) recipients under standard immunosuppression is uncertain. As part of an open-label, multicenter, prospective, phase IV, 24-month clinical trial (ClinicalTrials.gov, NCT02284464) in low-immunological-risk KT recipients, 105 patients were randomized, after a protocol-biopsy at 3 months, to corticosteroid continuation (CSC, n = 52) or corticosteroid withdrawal (CSW, n = 53). Both groups received tacrolimus and MMF and had another protocol-biopsy at 24 months. The acute rejection rate, including subclinical inflammation (SCI), was comparable between groups (21.2 vs. 24.5%). No patients developed dnDSA. Inflammatory and chronicity scores increased from 3 to 24 months in patients with, at baseline, no inflammation (NI) or SCI, regardless of treatment. CSW patients with SCI at 3 months had a significantly increased chronicity score at 24 months. HbA1c levels were lower in CSW patients (6.4 ± 1.2 vs. 5.7 ± 0.6%; p = 0.013) at 24 months, as was systolic blood pressure (134.2 ± 14.9 vs. 125.7 ± 15.3 mmHg; p = 0.016). Allograft function was comparable between groups and no patients died or lost their graft. An increase in chronicity scores at 2-years post-transplantation was observed in low-immunological-risk KT recipients with initial NI or SCI, but CSW may accelerate chronicity changes, especially in patients with early SCI. This strategy did, however, improve the cardiovascular profiles of patients.

Therapies for Chronic Allograft Rejection

Remarkable advances have been made in the pathophysiology, diagnosis, and treatment of antibody-mediated rejection (ABMR) over the past decades, leading to improved graft outcomes. However, long-term failure is still high and effective treatment for chronic ABMR, an important cause of graft failure, has not yet been identified. Chronic ABMR has a relatively different phenotype from active ABMR and is a slowly progressive disease in which graft injury is mainly caused by de novo donor specific antibodies (DSA). Since most trials of current immunosuppressive therapies for rejection have focused on active ABMR, treatment strategies based on those data might be less effective in chronic ABMR. A better understanding of chronic ABMR may serve as a bridge in establishing treatment strategies to improve graft outcomes. In this in-depth review, we focus on the pathophysiology and characteristics of chronic ABMR along with the newly revised Banff criteria in 2017. In addition, in terms of chronic ABMR, we identify the reasons for the resistance of current immunosuppressive therapies and look at ongoing research that could play a role in setting better treatment strategies in the future. Finally, we review non-invasive biomarkers as tools to monitor for rejection.

Impact of Subclinical Borderline Inflammation on Kidney Transplant Outcomes

Supplemental Digital Content is available in the text.

Background.

Surveillance biopsies permit early detection of subclinical inflammation before clinical dysfunction, but the impact of detecting early subclinical phenotypes remains unclear.

Methods.

We conducted a single-center retrospective cohort study of 441 consecutive kidney transplant recipients between 2015 and 2018 with surveillance biopsies at 6 months post-transplant. We tested the hypothesis that early subclinical inflammation (subclinical borderline changes, T cell-mediated rejection, or microvascular injury) is associated with increased incidence of a composite endpoint including acute rejection and allograft failure.

Results.

Using contemporaneous Banff criteria, we detected subclinical inflammation in 31%, with the majority (75%) having a subclinical borderline phenotype (at least minimal inflammation with mild tubulitis [>i0t1]). Overall, subclinical inflammation was independently associated with the composite endpoint (adjusted hazard ratio, 2.88; 1.11-7.51; P = 0.03). The subgroup with subclinical borderline inflammation, predominantly those meeting the Banff 2019 i1t1 threshold, was independently associated with 5-fold increased hazard for the composite endpoint (P = 0.02). Those with concurrent subclinical inflammation and subclinical chronic allograft injury had worse outcomes. The effect of treating subclinical inflammation was difficult to ascertain in small heterogeneous subgroups.

Conclusions.

Subclinical acute and chronic inflammation are common at 6 months post-transplant in kidney recipients with stable allograft function. The subclinical borderline phenotype with both tubulitis and interstitial inflammation was independently associated with poor long-term outcomes. Further studies are needed to elucidate the role of surveillance biopsies for management of allograft inflammation in kidney transplantation.

Economic analysis of screening for subclinical rejection in kidney transplantation using protocol biopsies and noninvasive biomarkers

Subclinical rejection (SCR) screening in kidney transplantation (KT) using protocol biopsies and noninvasive biomarkers has not been evaluated from an economic perspective. We assessed cost-effectiveness from the health sector perspective of SCR screening in the first year after KT using a Markov model that compared no screening with screening using protocol biopsy or biomarker at 3 months, 12 months, 3 and 12 months, or 3, 6, and 12 months. We used 12% subclinical cellular rejection and 3% subclinical antibody-mediated rejection (SC-ABMR) for the base-case cohort. Results favored 1-time screening at peak SCR incidence rather than repeated screening. Screening 2 or 3 times was favored only with age <35 years and with high SC-ABMR incidence. Compared to biomarkers, protocol biopsy yielded more quality-adjusted life years (QALYs) at lower cost. A 12-month biopsy cost $13 318/QALY for the base-case cohort. Screening for cellular rejection in the absence of SC-ABMR was less cost effective with 12-month biopsy costing $46 370/QALY. Screening was less cost effective in patients >60 years. Using biomarker twice or thrice was cost effective only if biomarker cost was <$700. In conclusion, in KT, screening for SCR more than once during the first year is not economically reasonable. Screening with protocol biopsy was favored over biomarkers.

Adequate tacrolimus exposure modulates the impact of HLA class II molecular mismatch: a validation study in an American cohort

Clinicians have few tools to predict the risk of alloimmune injury that would guide immunosuppression management in renal transplant patients. We evaluated human leukocyte antigen (HLA)-DR/DQ molecular mismatch to predict de novo donor-specific antibodies (DSAs) during the first year of transplant and explored how differences in tacrolimus exposure may modulate this risk. HLA-DR and -DQ eplet mismatches were determined between 444 donor-recipient pairs in Denver, Colorado between 2007 and 2013. Previously defined mismatch thresholds stratified recipients into low- (N = 119), intermediate- (N = 153), and high- (N = 172) risk categories. The area under the curve for DSA at 1 year was 0.84 and 0.82 for HLA-DR and HLA-DQ eplet mismatches, respectively. Compared to low-risk patients, there was a graded increase in risk of DR/DQ DSA in intermediate (HR 15.39, 95% CI 2.01-118.09, p = .009) and high-risk (HR 23.81, 95% CI 3.17-178.66, p = 0.002) categories. Intermediate- and high-risk patients with a mean tacrolimus <6 ng/ml versus >8 ng/ml had increased risk of DR/DQ DSA at 1 year (HR 2.34, 95% CI 1.05-5.22, p = .04). HLA molecular mismatch represents a reproducible, objective, and clinically relevant tool to stratify patients by alloimmune risk and may help guide personalized immunosuppression management.

Avoiding surveillance biopsy: Use of a noninvasive biomarker assay in a real-life scenario

PURPOSE

TruGraf™ blood test measures a specific gene expression signature in peripheral blood mononuclear cells for noninvasive assessment of kidney transplant recipients (KTRs) with stable renal function, excluding subclinical acute rejection (subAR) with high degree of confidence. Study objective was to correlate TruGraf™ test with 6-month surveillance biopsy (SBx).

METHODS

Prospective, single-center study of 116 consecutive KTRs with SBx performed at 6 months post-transplant..TruGraf™ done at time of SBx; results compared with histology (Banff 2017) for concordance.

RESULTS

Of 116 enrollees, 26 excluded, absent biopsy (n = 17), test quality control issues (n = 9), leaving 90 KTRs-66% deceased donor kidneys, 58% African American, and 59% male. TruGraf™ result negative in 67 subjects; 54 had normal biopsy, indicating SBx could have been avoided. Eight subjects had true positive result where biopsy justified. Unnecessary biopsy would have been performed in 15 subjects with false-positive TruGraf™, and subAR missed in 13 subjects with false-negative test. In overall population of 90 patients, SBx would have been avoided in 54 (60%).

CONCLUSIONS

Implementation of TruGraf™ testing in a "real-world" cohort at the time of SBx identified a significant proportion of KTRs that could have avoided SBx.

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection

Prognostic biomarkers of T cell-mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA-DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor-specific antibodies (P = .002). HLA-DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA-DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA-DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA-DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA-DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

Kidney Graft Surveillance Biopsy Utilization and Trends: Results From a Survey of High-Volume Transplant Centers

An e-mail-based market research survey focused on high-volume US adult transplant centers was developed and implemented to assess surveillance based on United Network for Organ Sharing/Scientific Registry of Transplant Recipients data: 51 to 100 transplants, 101 to 200 transplants, and more than 200 transplants. Eighty-three centers responded to the survey. Respondent centers represented 13,837/21,167 (65%) of the total kidney transplants in 2018. In total, 38/83 (46%) centers reported the use of surveillance biopsies-20 centers in all patients and 18 in select patients. Surveillance biopsies were performed in 37% (7/19) of centers performing 51 to 100 transplants annually, in 44% (15/34) doing 101 to 200 transplants, and in 53% (16/30) of centers doing more than 200 transplants. Of the 20 centers doing surveillance biopsies in all patients, 17/20 (85%) perform more than 100 annual transplants, and 3/20 (15%) perform less than 100 annual transplants. Of the 45 centers not currently doing surveillance biopsies, 13 (29%) used surveillance biopsies in the past; discontinuation was primarily due to patient inconvenience, adverse events, and cost. Using survey percentages, it is estimated that surveillance biopsies are performed in approximately 34% of kidney transplant recipients and that 74% of all surveillance biopsies occur in centers performing more than 100 kidney transplants per year.

Discrepancy analysis comparing molecular and histology diagnoses in kidney transplant biopsies

Discrepancy analysis comparing two diagnostic platforms offers potential insights into both without assuming either is always correct. Having optimized the Molecular Microscope Diagnostic System (MMDx) in renal transplant biopsies, we studied discrepancies within MMDx (reports and sign-out comments) and between MMDx and histology. Interpathologist discrepancies have been documented previously and were not assessed. Discrepancy cases were classified as "clear" (eg, antibody-mediated rejection [ABMR] vs T cell-mediated rejection [TCMR]), "boundary" (eg, ABMR vs possible ABMR), or "mixed" (eg, Mixed vs ABMR). MMDx report scores showed 99% correlations; sign-out interpretations showed 7% variation between observers, all located around boundaries. Histology disagreed with MMDx in 37% of biopsies, including 315 clear discrepancies, all with implications for therapy. Discrepancies were distributed widely in all histology diagnoses but increased in some scenarios; for example, histology TCMR contained 14% MMDx ABMR and 20% MMDx no rejection. MMDx usually gave unambiguous diagnoses in cases with ambiguous histology, for example, borderline and transplant glomerulopathy. Histology lesions or features associated with more frequent discrepancies (eg, tubulitis, arteritis, and polyomavirus nephropathy) were not associated with increased MMDx uncertainty, indicating that MMDx can clarify biopsies with histologic ambiguity. The patterns of histology-MMDx discrepancies highlight specific histology diagnoses in which MMDx assessment should be considered for guiding therapy.

Transcriptional dissection of differentially expressed long non-coding RNAs and messenger RNAs reveals the potential molecular mechanism after kidney transplantation

Background

Kidney transplantation has given benefits to patients, although the associated genetic mechanisms are unclear. The present study aimed to understand the changes in gene expression and genetic pathways after kidney transplantation with the administration of immunosuppressive drugs.

Methods

The transcriptome data of blood samples from kidney transplantation recipients, obtained by RNA-seq, were reannotated to a more complete human genome (GRCh38/hg38). We compared the differentially expressed genes (DEGs) at pretransplant and 1 week, 3 months and 6 months posttransplant; researched the temporal variation of the DEGs; and constructed a long non-coding RNA (lncRNA)-messenger RNA (mRNA) network.

Results

We found that compared to that at pretransplantation, 1,766 genes and 3,530 genes were upregulated and downregulated, respectively, at 1 week after kidney transplantation, and the number of DEGs declined over time. These DEGs were separated into 16 clusters, and the temporal variation expression was established by the average expression of the DEGs. A pathway analysis suggested that the immune reaction was attenuated and that the expression of ribosome-related proteins was reduced.

Conclusions

The lncRNA-mRNA network had 235 connections between 138 lncRNAs and 170 mRNAs. This work generated a gene profile based on temporal variation and revealed a significantly altered lncRNA-mRNA axis contributing to molecular regulation, suggesting the potential gene mechanism of kidney transplantation and the effects of immunosuppressive drugs.