A Randomized Phase 2 Trial of Felzartamab in Antibody-Mediated Rejection.

BACKGROUND: Antibody-mediated rejection is a leading cause of kidney-transplant failure. The targeting of CD38 to inhibit graft injury caused by alloantibodies and natural killer (NK) cells may be a therapeutic option. METHODS: In this phase 2, double-blind, randomized, placebo-controlled trial, we assigned patients with antibody-mediated rejection that had occurred at least 180 days after transplantation to receive nine infusions of the CD38 monoclonal antibody felzartamab (at a dose of 16 mg per kilogram of body weight) or placebo for 6 months, followed by a 6-month observation period. The primary outcome was the safety and side-effect profile of felzartamab. Key secondary outcomes were renal-biopsy results at 24 and 52 weeks, donor-specific antibody levels, peripheral NK-cell counts, and donor-derived cell-free DNA levels. RESULTS: A total of 22 patients underwent randomization (11 to receive felzartamab and 11 to receive placebo). The median time from transplantation until trial inclusion was 9 years. Mild or moderate infusion reactions occurred in 8 patients in the felzartamab group. Serious adverse events occurred in 1 patient in the felzartamab group and in 4 patients in the placebo group; graft loss occurred in 1 patient in the placebo group. At week 24, resolution of morphologic antibody-mediated rejection was more frequent with felzartamab (in 9 of 11 patients [82%]) than with placebo (in 2 of 10 patients [20%]), for a difference of 62 percentage points (95% confidence interval [CI], 19 to 100) and a risk ratio of 0.23 (95% confidence interval [CI], 0.06 to 0.83). The median microvascular inflammation score was lower in the felzartamab group than in the placebo group (0 vs. 2.5), for a mean difference of -1.95 (95% CI, -2.97 to -0.92). Also lower was a molecular score reflecting the probability of antibody-mediated rejection (0.17 vs. 0.77) and the level of donor-derived cell-free DNA (0.31% vs. 0.82%). At week 52, the recurrence of antibody-mediated rejection was reported in 3 of 9 patients who had a response to felzartamab, with an increase in molecular activity and biomarker levels toward baseline levels. CONCLUSIONS: Felzartamab had acceptable safety and side-effect profiles in patients with antibody-mediated rejection. (Funded by MorphoSys and Human Immunology Biosciences; ClinicalTrials.gov number, NCT05021484; and EUDRACT number, 2021-000545-40.).

Results of Two Cases of Pig-to-Human Kidney Xenotransplantation.

BACKGROUND: Xenografts from genetically modified pigs have become one of the most promising solutions to the dearth of human organs available for transplantation. The challenge in this model has been hyperacute rejection. To avoid this, pigs have been bred with a knockout of the alpha-1,3-galactosyltransferase gene and with subcapsular autologous thymic tissue. METHODS: We transplanted kidneys from these genetically modified pigs into two brain-dead human recipients whose circulatory and respiratory activity was maintained on ventilators for the duration of the study. We performed serial biopsies and monitored the urine output and kinetic estimated glomerular filtration rate (eGFR) to assess renal function and xenograft rejection. RESULTS: The xenograft in both recipients began to make urine within moments after reperfusion. Over the 54-hour study, the kinetic eGFR increased from 23 ml per minute per 1.73 m2 of body-surface area before transplantation to 62 ml per minute per 1.73 m2 after transplantation in Recipient 1 and from 55 to 109 ml per minute per 1.73 m2 in Recipient 2. In both recipients, the creatinine level, which had been at a steady state, decreased after implantation of the xenograft, from 1.97 to 0.82 mg per deciliter in Recipient 1 and from 1.10 to 0.57 mg per deciliter in Recipient 2. The transplanted kidneys remained pink and well-perfused, continuing to make urine throughout the study. Biopsies that were performed at 6, 24, 48, and 54 hours revealed no signs of hyperacute or antibody-mediated rejection. Hourly urine output with the xenograft was more than double the output with the native kidneys. CONCLUSIONS: Genetically modified kidney xenografts from pigs remained viable and functioning in brain-dead human recipients for 54 hours, without signs of hyperacute rejection. (Funded by Lung Biotechnology.).

Interferon-γ and its response are determinants of antibody-mediated rejection and clinical outcomes in patients after renal transplantation.

Interferon-γ (IFN-γ) is an important cytokine in tissue homeostasis and immune response, while studies about it in antibody-mediated rejection (ABMR) are very limited. This study aims to comprehensively elucidate the role of IFN-γ in ABMR after renal transplantation. In six renal transplantation cohorts, the IFN-γ responses (IFNGR) biological process was consistently top up-regulated in ABMR compared to stable renal function or even T cell-mediated rejection in both allografts and peripheral blood. According to single-cell analysis, IFNGR levels were found to be broadly elevated in most cell types in allografts and peripheral blood with ABMR. In allografts with ABMR, M1 macrophages had the highest IFNGR levels and were heavily infiltrated, while kidney resident M2 macrophages were nearly absent. In peripheral blood, CD14+ monocytes had the top IFNGR level and were significantly increased in ABMR. Immunofluorescence assay showed that levels of IFN-γ and M1 macrophages were sharply elevated in allografts with ABMR than non-rejection. Importantly, the IFNGR level in allografts was identified as a strong risk factor for long-term renal graft survival. Together, this study systematically analyzed multi-omics from thirteen independent cohorts and identified IFN-γ and IFNGR as determinants of ABMR and clinical outcomes in patients after renal transplantation.

Banff 2022 Vascularized Composite Allotransplantation Meeting Report: Diagnostic criteria for vascular changes.

As more data become available, the Banff 2007 working classification of skin-containing vascularized composite allograft (VCA) pathology is expected to evolve and develop. This report represents the Banff VCA Working Group's consensus on the first revision of the 2007 scoring system. Prior to the 2022 Banff-CanXadian Society of Transplantation Joint Meeting, 83 clinicians and/or researchers were invited to a virtual meeting to discuss whether the 2007 Banff VCA system called for a revision. Unanimously, it was determined that the vascular changes were to be included in the first revision. Subsequently, 2 international online surveys, each followed by virtual discussions, were launched. The goals were (1) to identify which changes define severe rejection, (2) to grade their importance in the evaluation of severe rejection, and (3) to identify emerging criteria to diagnose rejection. A final hybrid (in-person and virtual) discussion at the Banff/Canadian Society of Transplantation Joint Meeting finalized the terminology, the definition, a scoring system, and a reporting system of the vascular changes. This proposal represents an international consensus on this topic and establishes the first revision of the Banff 2007 working classification of skin-containing vascularized composite allograft pathology.

The 2022 Banff Meeting Lung Report.

The Lung Session of the 2022 16th Banff Foundation for Allograft Pathology Conference-held in Banff, Alberta-focused on non-rejection lung allograft pathology and novel technologies for the detection of allograft injury. A multidisciplinary panel reviewed the state-of-the-art of current histopathologic entities, serologic studies, and molecular practices, as well as novel applications of digital pathology with artificial intelligence, gene expression analysis, and quantitative image analysis of chest computerized tomography. Current states of need as well as prospective integration of the aforementioned tools and technologies for complete assessment of allograft injury and its impact on lung transplant outcomes were discussed. Key conclusions from the discussion were: (1) recognition of limitations in current standard of care assessment of lung allograft dysfunction; (2) agreement on the need for a consensus regarding the standardized approach to the collection and assessment of pathologic data, inclusive of all lesions associated with graft outcome (eg, non-rejection pathology); and (3) optimism regarding promising novel diagnostic modalities, especially minimally invasive, which should be integrated into large, prospective multicenter studies to further evaluate their utility in clinical practice for directing personalized therapies to improve graft outcomes.

The Banff 2022 Kidney Meeting Work Plan: Data-driven refinement of the Banff Classification for renal allografts.

The XVIth Banff Meeting for Allograft Pathology was held in Banff, Alberta, Canada, from September 19 to 23, 2022, as a joint meeting with the Canadian Society of Transplantation. In addition to a key focus on the impact of microvascular inflammation and biopsy-based transcript analysis on the Banff Classification, further sessions were devoted to other aspects of kidney transplant pathology, in particular T cell-mediated rejection, activity and chronicity indices, digital pathology, xenotransplantation, clinical trials, and surrogate endpoints. Although the output of these sessions has not led to any changes in the classification, the key role of Banff Working Groups in phrasing unanswered questions, and coordinating and disseminating results of investigations addressing these unanswered questions was emphasized. This paper summarizes the key Banff Meeting 2022 sessions not covered in the Banff Kidney Meeting 2022 Report paper and also provides an update on other Banff Working Group activities relevant to kidney allografts.

Banff 2022 Liver Group Meeting report: Monitoring long-term allograft health.

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participants included hepatologists, surgeons, pathologists, immunologists, and histocompatibility specialists. Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimization, and long-term structural changes. Potential revision of the rejection classification scheme to better accommodate and communicate late T cell-mediated rejection patterns and related structural changes, such as nodular regenerative hyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression to match the heterogeneity of patient settings will be central to improving long-term patient survival. Such personalized therapeutics are in turn contingent on a better understanding and monitoring of allograft status within a rational decision-making approach, likely to be facilitated in implementation with emerging decision-support tools. Proposed revisions to rejection classification emerging from the meeting include the incorporation of interface hepatitis and fibrosis staging. These will be opened to online testing, modified accordingly, and subject to consensus discussion leading up to the next Banff conference.

Belatacept with time-limited tacrolimus coimmunosuppression modifies the 3-year risk of eplet mismatch in kidney transplantation.

Solid organ transplant donor-recipient eplet mismatch has been correlated with donor-specific antibody (DSA) formation, antibody-mediated rejection, and overall rejection rates. However, studies have been predominantly in patients on tacrolimus-based immunosuppression regimens and have not fully explored differences in ethnically and racially diverse populations. Evidence indicates that patients on belatacept have lower rates of DSA formation, suggesting mediation of the immunogenicity of mismatched human leukocyte antigen polymorphisms. We performed a retrospective, single-center analysis of class II eplet disparity in a cohort of kidney transplant recipients treated using belatacept with tacrolimus induction (Bela/TacTL) or tacrolimus regimens between 2016 and 2019. Bela/TacTL (n = 294) and tacrolimus (n = 294) cohorts were propensity score-matched with standardized difference <0.15. Single-molecule eplet risk level was associated with immune event rates for both groups. In Cox regression analysis stratified by eplet risk level, Bela/TacTL immunosuppression was associated with a decreased rate of DSA (hazard ratio [HR] = 0.4), antibody-mediated rejection (HR = 0.2), and rejection (HR = 0.45). In the low-risk group, cumulative graft failure was lower for patients on Bela/TacTL (P < .02). Analysis of eplet mismatch burden may be a useful adjunct in identifying high-risk populations with increased immunosuppression requirements and should encourage the design of allocation rules to incentivize lower-risk pairings without negatively impacting equity in access.

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.

Xenotransplantation experiments in brain-dead human subjects-A critical appraisal.

Brain-dead human subjects (decedents) were recently introduced as a potential preclinical experimental model in xenotransplantation. Brain death is associated with major pathophysiological changes, eg, structural injury and cell infiltration in vital organs, and major hormonal, metabolic, inflammatory, and hemodynamic changes. In 2 of the 3 initial experiments, the design of the experiments resulted in little or no new information becoming available. In the third, the experiment was unfortunately unsuccessful as neither of the 2 pig kidneys transplanted into the decedent functioned adequately. Failure may well have been associated with the effects of brain death, but an immune/inflammatory response to the xenograft could not be excluded. Subsequently, 2 further pig kidney transplants and 2 pig heart transplants have been carried out in human decedents, but again the data obtained do not add much to what is already known. In view of the profound changes that take place during and after brain death, it may prove difficult to determine whether graft failure or dysfunction results from the effects of brain death or from an immune/inflammatory response to the xenograft. A major concern is that, if the results are confusing, they may impact decisions relating to the introduction of clinical xenotransplantation.

Applying propensity methods to the United States transplant registry for external real-world evidence control arms for 5-year survival in the BENEFIT study.

To address the challenges of assessing the impact of a reasonably likely surrogate endpoint on long-term graft survival in prospective kidney transplant clinical trials, the Transplant Therapeutics Consortium established a real-world evidence workgroup evaluating the scientific value of using transplant registry data as an external control to supplement the internal control group. The United Network for Organ Sharing retrospectively simulated the use of several distinct contemporaneous external control groups, applied multiple cause inference methods, and compared treatment effects to those observed in the BENEFIT study. Applying BENEFIT study enrollment criteria produced a smaller historical cyclosporine control arm (n = 153) and a larger, alternative (tacrolimus) historical control arm (n = 1069). Following covariate-balanced propensity scoring, Kaplan-Meier 5-year all-cause graft survivals were 81.3% and 81.7% in the Organ Procurement and Transplantation Network (OPTN) tacrolimus and cyclosporine external control arms, similar to 80.3% observed in the BENEFIT cyclosporine treatment arm. Five-year graft survival in the belatacept-less intensive arm was significantly higher than the OPTN controls using propensity scoring for comparing cyclosporine and tacrolimus. Propensity weighting using OPTN controls closely mirrored the BENEFIT study's long-term control (cyclosporine) arm's survival rate and the less intensive arm's treatment effect (significantly higher survival vs control). This study supports the feasibility and validity of using supplemental external registry controls for long-term survival in kidney transplant clinical trials.

Exploring the single-cell immune landscape of kidney allograft inflammation using imaging mass cytometry.

Kidney allograft inflammation, mostly attributed to rejection and infection, is an important cause of graft injury and loss. Standard histopathological assessment of allograft inflammation provides limited insights into biological processes and the immune landscape. Here, using imaging mass cytometry with a panel of 28 validated biomarkers, we explored the single-cell landscape of kidney allograft inflammation in 32 kidney transplant biopsies and 247 high-dimensional histopathology images of various phenotypes of allograft inflammation (antibody-mediated rejection, T cell-mediated rejection, BK nephropathy, and chronic pyelonephritis). Using novel analytical tools, for cell segmentation, we segmented over 900 000 cells and developed a tissue-based classifier using over 3000 manually annotated kidney microstructures (glomeruli, tubules, interstitium, and arteries). Using PhenoGraph, we identified 11 immune and 9 nonimmune clusters and found a high prevalence of memory T cell and macrophage-enriched immune populations across phenotypes. Additionally, we trained a machine learning classifier to identify spatial biomarkers that could discriminate between the different allograft inflammatory phenotypes. Further validation of imaging mass cytometry in larger cohorts and with more biomarkers will likely help interrogate kidney allograft inflammation in more depth than has been possible to date.

Temporal correlation between postreperfusion complement deposition and severe primary graft dysfunction in lung allografts.

Growing evidence implicates complement in the pathogenesis of primary graft dysfunction (PGD). We hypothesized that early complement activation postreperfusion could predispose to severe PGD grade 3 (PGD-3) at 72 hours, which is associated with worst posttransplant outcomes. Consecutive lung transplant patients (n = 253) from January 2018 through June 2023 underwent timed open allograft biopsies at the end of cold ischemia (internal control) and 30 minutes postreperfusion. PGD-3 at 72 hours occurred in 14% (35/253) of patients; 17% (44/253) revealed positive C4d staining on postreperfusion allograft biopsy, and no biopsy-related complications were encountered. Significantly more patients with PGD-3 at 72 hours had positive C4d staining at 30 minutes postreperfusion compared with those without (51% vs 12%, P < .001). Conversely, patients with positive C4d staining were significantly more likely to develop PGD-3 at 72 hours (41% vs 8%, P < .001) and experienced worse long-term outcomes. In multivariate logistic regression, positive C4d staining remained highly predictive of PGD-3 (odds ratio 7.92, 95% confidence interval 2.97-21.1, P < .001). Hence, early complement deposition in allografts is highly predictive of PGD-3 at 72 hours. Our data support future studies to evaluate the role of complement inhibition in patients with early postreperfusion complement activation to mitigate PGD and improve transplant outcomes.

Smoking exposure-induced bronchus-associated lymphoid tissue in donor lungs does not prevent tolerance induction after transplantation.

The presence of bronchus-associated lymphoid tissue (BALT) in donor lungs has been suggested to accelerate graft rejection after lung transplantation. Although chronic smoke exposure can induce BALT formation, the impact of donor cigarette use on alloimmune responses after lung transplantation is not well understood. Here, we show that smoking-induced BALT in mouse donor lungs contains Foxp3+ T cells and undergoes dynamic restructuring after transplantation, including recruitment of recipient-derived leukocytes to areas of pre-existing lymphoid follicles and replacement of graft-resident donor cells. Our findings from mouse and human lung transplant data support the notion that a donor's smoking history does not predispose to acute cellular rejection or prevent the establishment of allograft acceptance with comparable outcomes to nonsmoking donors. Thus, our work indicates that BALT in donor lungs is plastic in nature and may have important implications for modulating proinflammatory or tolerogenic immune responses following transplantation.

Advancing mouse models for transplantation research.

Mouse models have been instrumental in understanding mechanisms of transplant rejection and tolerance, but cross-study reproducibility and translation of experimental findings into effective clinical therapies are issues of concern. The Mouse Models in Transplantation symposium gathered scientists and physician-scientists involved in basic and clinical research in transplantation to discuss the strengths and limitations of mouse transplant models and strategies to enhance their utility. Participants recognized that increased procedure standardization, including the use of prespecified, defined endpoints, and statistical power analyses, would benefit the field. They also discussed the generation of new models that incorporate environmental and genetic variables affecting clinical outcomes as potentially important. If implemented, these strategies are expected to improve the reproducibility of mouse studies and increase their translation to clinical trials and, ideally, new Food and Drug Administration-approved drugs.

Fibrotic progression from acute cellular rejection is dependent on secondary lymphoid organs in a mouse model of chronic lung allograft dysfunction.

Chronic lung allograft dysfunction (CLAD) remains one of the major limitations to long-term survival after lung transplantation. We modified a murine model of CLAD and transplanted left lungs from BALB/c donors into B6 recipients that were treated with intermittent cyclosporine and methylprednisolone postoperatively. In this model, the lung allograft developed acute cellular rejection on day 15 which, by day 30 after transplantation, progressed to severe pleural and peribronchovascular fibrosis, reminiscent of changes observed in restrictive allograft syndrome. Lung transplantation into splenectomized B6 alymphoplastic (aly/aly) or splenectomized B6 lymphotoxin-ß receptor-deficient mice demonstrated that recipient secondary lymphoid organs, such as spleen and lymph nodes, are necessary for progression from acute cellular rejection to allograft fibrosis in this model. Our work uncovered a critical role for recipient secondary lymphoid organs in the development of CLAD after pulmonary transplantation and may provide mechanistic insights into the pathogenesis of this complication.

Impact of deceased organ donor marijuana use on donor culture positivity and solid organ transplant recipient outcomes.

With the increasing prevalence of marijuana use in the US, many deceased organ donors have a history of marijuana use, raising concerns about infectious risks to transplant recipients. We performed a multicenter retrospective cohort study in which exposed donors were those with recent marijuana use (in the prior 12 months) and unexposed donors were those with no recent marijuana use. Primary outcomes included the following: (1) positive donor cultures for bacteria or fungi, (2) recipient infection due to bacteria or fungi within 3 months posttransplant, and (3) recipient graft failure or death within 12 months posttransplant. Multivariable regression was used to evaluate the relationship between donor marijuana use and each outcome. A total of 658 recipients who received organs from 394 donors were included. Recent marijuana use was not associated with donor culture positivity (aOR: 0.84, 95% CI: 0.39-1.81, P = .65), recipient infection (aHR: 1.02, 95% CI: 0.76-1.38, P = .90), or recipient graft failure or death (aHR: 1.65, 95% CI: 0.90-3.02, P = .11). Our data suggest that organs from donors with a history of recent marijuana use do not pose significant infectious risks in the early posttransplant period.

Comparing the prognostic performance of iBOX and biopsy-proven acute rejection for long-term kidney graft survival.

Biopsy-proven acute rejection (BPAR) occurs in approximately 10% of kidney transplant recipients in the first year, making superiority trials unfeasible. iBOX, a quantitative composite of estimated glomerular filtration rate, proteinuria, antihuman leukocyte antigen donor-specific antibody, and + full/- abbreviated kidney histopathology, is a new proposed surrogate endpoint. BPAR's prognostic ability was compared with iBOX in a pooled cohort of 1534 kidney transplant recipients from 4 data sets, including 2 prospective randomized controlled trials. Discrimination analyses showed mean c-statistic differences between both iBOX compared with BPAR of 0.25 (95% confidence interval: 0.17-0.32) for full iBOX and 0.24 (95% confidence interval: 0.16-0.32) for abbreviated iBOX, indicating statistically significantly higher c-statistic values for the iBOX prognosis of death-censored graft survival. Mean (± standard error) c-statistics were 0.81 ± 0.03 for full iBOX, 0.80 ± 0.03 for abbreviated iBOX, and 0.57 ± 0.03 for BPAR. In calibration analyses, predicted graft loss events from both iBOX models were not significantly different from those observed. However, for BPAR, the predicted events were significantly (P < .01) different (observed: 64; predicted: 70; full iBOX: 76; abbreviated iBOX: 173 BPAR). IBOX at 1-year posttransplant is superior to BPAR in the first year posttransplant in graft loss prognostic performance, providing valuable additional information and facilitating the demonstration of superiority of novel immunosuppressive regimens.

Neonatal islets from human PD-L1 transgenic pigs reduce immune cell activation and cellular rejection in humanized nonobese diabetic-scid IL2rγnull mice.

Strong xenorejection limits the clinical application of porcine islet transplantation in type 1 diabetes. Targeting T cell-mediated rejection is one of the main approaches to improve long-term graft survival. Here we study engraftment and survival of porcine islet cells expressing human programmed cell death ligand-1 (hPD-L1) in a humanized mouse model. Neonatal islet-like clusters (NPICCs) from transgenic hPD-L1 (hPD-L1-Tg) and wild-type (Wt) pigs were transplanted into nonobese diabetic-scid IL2rγnull mice stably reconstituted with human immune cells (hPD-L1 n = 10; Wt n = 6). Primary endpoint was development of normoglycemia during a 16-week observation period after transplantation. Secondary endpoints were porcine C-peptide levels and immune cell infiltration. Animals transplanted with hPD-L1-Tg neonatal islet-like clusters achieved a superior normoglycemic rate (50% versus 0%) and significantly higher plasma C-peptide levels as compared to the Wt group, indicating long-term beta cell function. Intracytoplasmic fluorescence-activated cell sorting analysis and immunohistochemistry revealed significantly decreased frequencies of interferonγ-expressing splenic hCD8-positive T cells and reduced intragraft-infiltrating immune cells. We here demonstrate that expression of hPD-L1 provides strong islet xenograft protection without administration of immunosuppressive drugs. These findings support the hypothesis that hPD-L1 has the capacity to control cellular rejection and therefore represents a very promising transgene candidate for clinical porcine islet xenotransplantation.

Exploring kidney allograft rejection: A proof-of-concept study using spatial transcriptomics.

In this proof-of-concept study, spatial transcriptomics combined with public single-cell ribonucleic acid-sequencing data were used to explore the potential of this technology to study kidney allograft rejection. We aimed to map gene expression patterns within diverse pathologic states by examining biopsies classified across nonrejection, T cell-mediated acute rejection, interstitial fibrosis, and tubular atrophy. Our results revealed distinct immune cell signatures, including those of T and B lymphocytes, monocytes, mast cells, and plasma cells, and their spatial organization within the renal interstitium. We also mapped chemokine receptors and ligands to study immune cell migration and recruitment. Finally, our analysis demonstrated differential spatial enrichment of transcription signatures associated with kidney allograft rejection across various biopsy regions. Interstitium regions displayed higher enrichment scores for rejection-associated gene expression patterns than tubular areas, which had negative scores. This implies that these signatures are primarily driven by processes unfolding in the renal interstitium. Overall, this study highlights the value of spatial transcriptomics for revealing cellular heterogeneity and immune signatures in renal transplant biopsies and demonstrates its potential for studying the molecular and cellular mechanisms associated with rejection. However, certain limitations must be borne in mind regarding the development and future applications of this technology.