Rejected Kidney Transplants Research Articles

Plasma-Derived Extracellular Vesicles of Antibody-Mediated Allograft Rejection Kidney Transplant Patients Mediate Reprogramming of Human Podocytes: Role of SGLT2 Inhibitors

Plasma-Derived Extracellular Vesicles of Antibody-Mediated Allograft Rejection Kidney Transplant Patients Mediate Reprogramming of Human Podocytes: Role of SGLT2 Inhibitors

FOS+ Macrophages Promote Chronic Rejection of Cardiac Transplantation.

Chronic rejection remains the leading cause of progressive decline in graft function. Accumulating evidence indicates that macrophages participate in chronic rejection dependent on CD40-CD40L. The FOS family members are critical in inflammatory and immune responses. However, the mechanisms underlying the role of FOS family members in chronic rejection remain unclear. In this study, we aimed to elucidate the role and underlying mechanisms of FOS-positive macrophages regulated by CD40 that mediate chronic allograft rejection. We downloaded publicly accessible chronic rejection kidney transplant single-cell sequencing datasets from the gene expression omnibus database. Differentially expressed genes between the CD40hi and CD40low macrophage chronic rejection groups were analyzed. We established a chronic rejection mouse model by using CTLA-4-Ig. We treated bone marrow-derived macrophages with an anti-CD40 antibody. We assessed expression of the FOS family by flow cytometry, real-time quantitative polymerase chain reaction, Western blotting, and immunofluorescence. We identified altered signaling pathways by using RNA sequencing analysis. We detected DNA specifically bound to transcription factors by using ChIP-sequencing, with detection of the degree of graft fibrosis and survival. FOS was highly expressed on CD40hi macrophages in patients with chronic transplantrejection. Mechanistically, we showed that CD40 activated NF-κB2 translocation into the nucleus to upregulate c-Fos and FosB expression, thus promoting chronic rejection of cardiac transplant.We showed thatNF-κB2 regulated c-Fos and FosB expression by binding to the c-fos and fosb promoter regions. Inhibition of c-Fos/activator protein-1 decreased graft fibrosis and prolonged graft survival. CD40 may activate transcription factor NF-κB2 translocation into the nucleus of macrophages to upregulate c-Fos and FosB expression, thus promoting chronic rejection of cardiac transplant. Inhibition of c-Fos/activator protein-1 decreased grafts fibrosis and prolonged graft survival.

#2129 Tacrolimus-extended-release versus tacrolimus LCPT: preliminary data

Abstract Background and Aims To prevent rejection kidney transplant recipients are treated with immunosuppressive drugs, like tacrolimus. The dosage needed to reach therapeutic trough levels of tacrolimus greatly varies between patients. Currently, there are two tacrolimus extended-release variants on the market. Tacrolimus-extended release (Tac-ER/Advagraf) and tacrolimus LCPT (Tac-LCPT/Envarsus). Tac-LCPT was developed using Meltdose technology to improve absorption. Studies suggest that with Tac-LCPT therapeutic levels can be reached with a lower total dose as compared to Tac-ER. We aim to investigate if the dose needed to reach therapeutic trough levels of tacrolimus can be reduced when using Tac-LCPT as compared to Tac-ER in patients who need a relatively high dose. Method A prospective open-label switch design study was performed in patients 6 months up to 5 years after receiving a kidney transplant, who received Tac-ER, with therapeutic trough levels, and a concentration/dosage ratio (CDR) <1.05 ng/mlx1/mg. Patients were switched from Tac-ER to Tac-LCPT with a dose reduction of 30% for 3 weeks. After these 3 weeks, they were switched back to their original dose of Tac-ER. Total follow-up was 6 weeks with weekly visits for adjustment of the dosage. The primary outcome was the dose of Tac-LCPT needed to reach therapeutic trough levels as compared to Tac-ER. Secondary outcomes were side effects and pill burden. Results For this preliminary analysis, 8 kidney transplant recipients were included. At baseline, the median age was 52.5 (IQR 44.5, 57.0) years old, 75% of patients were male, and the median number of months after transplantation was 14.2 (IQR 11.50, 16.08). The median dose of Tac-ER needed at baseline was 9.0 mg (IQR 8.0, 11.25) with a CDR of 0.89 (IQR 0.68, 0.92). The tacrolimus dosage needed to reach therapeutic trough levels was significantly lower with Tac-LCPT compared to Tac-ER (5.5 mg vs. 9.5 mg, p = 0.03). However, the patients experiencing side effects and the pill burden did not change between the formulations. The Cmax of Tac-ER and Tac-LCPT varied between patients, with no significant difference between formulations (Fig. 1). At the end of the study, two patients preferred to continue Tac-LCPT, one patient preferred Tac-ER and the remaining patients had no preference. Conclusion In conclusion, the total needed dosage of tacrolimus to obtain therapeutic trough levels with Tac-LCPT is smaller than with Tac-ER. However, this smaller dosage administered did not translate to fewer side effects, a smaller pill burden, or a lower peak concentration. When inclusion is completed, additional pharmacokinetics will be calculated as well as the determination of CYP3A5 polymorphisms.

PCR Array Technology in Biopsy Samples Identifies Up-Regulated mTOR Pathway Genes as Potential Rejection Biomarkers After Kidney Transplantation.

Background: Antibody-mediated rejection (AMR) is the major cause of kidney transplant rejection. The donor-specific human leukocyte antigen (HLA) antibody (DSA) response to a renal allograft is not fully understood yet. mTOR complex has been described in the accommodation or rejection of transplants and integrates responses from a wide variety of signals. The aim of this study was to analyze the expression of the mTOR pathway genes in a large cohort of kidney transplant patients to determine its possible influence on the transplant outcome.Methods: A total of 269 kidney transplant patients monitored for DSA were studied. The patients were divided into two groups, one with recipients that had transplant rejection (+DSA/+AMR) and a second group of recipients without rejection (+DSA/–AMR and –DSA/–AMR, controls). Total RNA was extracted from kidney biopsies and reverse transcribed to cDNA. Human mTOR-PCR array technology was used to determine the expression of 84 mTOR pathway genes. STRING and REVIGO software were used to simulate gene to gene interaction and to assign a molecular function.Results: The studied groups showed a different expression of the mTOR pathway related genes. Recipients that had transplant rejection showed an over-expressed transcript (≥5-fold) of AKT1S1, DDIT4, EIF4E, HRAS, IGF1, INS, IRS1, PIK3CD, PIK3CG, PRKAG3, PRKCB (>12-fold), PRKCG, RPS6KA2, TELO2, ULK1, and VEGFC, compared with patients that did not have rejection. AKT1S1 transcripts were more expressed in +DSA/–AMR biopsies compared with +DSA/+AMR. The main molecular functions of up-regulated gene products were phosphotransferase activity, insulin-like grown factor receptor and ribonucleoside phosphate binding. The group of patients with transplant rejection also showed an under-expressed transcript (≥5-fold) of VEGFA (>15-fold), RPS6, and RHOA compared with the group without rejection. The molecular function of down-regulated gene products such as protein kinase activity and carbohydrate derivative binding proteins was also analyzed.Conclusions: We have found a higher number of over-expressed mTOR pathway genes than under-expressed ones in biopsies from rejected kidney transplants (+DSA/+AMR) with respect to controls. In addition to this, the molecular function of both types of transcripts (over/under expressed) is different. Therefore, further studies are needed to determine if variations in gene expression profiles can act as predictors of graft loss, and a better understanding of the mechanisms of action of the involved proteins would be necessary.

Phenotyping circulating endothelial cells as a marker for transplant kidney damage

Background & Aim The diagnosis of transplant rejection is mostly based on late and insensitive markers that do not reliably discriminate from other causes of kidney transplant injury. Early, specific and minimally-invasive biomarkers may improve rejection diagnosis. Endothelial cell (EC) layer damage is one of the reasons for the functional deterioration of rejecting kidney transplants. Bioassays quantifying circulating EC numbers and its characteristics as a read-out parameter is an attractive method to monitor kidney transplant integrity. Methods, Results & Conclusion We examined the association between the count and phenotypic characteristics of circulating EC from peripheral blood of kidney transplant recipients and clinical outcome, including allograft function (eGFR using creatinine). A cohort of 52 kidney recipients transplanted in 2019 was studied. Circulating EC were measured 1 day before transplantation and 3 and 7 days after transplantation. In addition, blood was sampled and analyzed whenever acute rejection was suspected throughout the first three months after transplantation. Flow cytometry assessed the number of circulating EC by staining for CD31, CD34, CD45, CD105, CD133, and CD146. This panel also included, the kidney injury molecule (KIM1). Data analysis was performed using a non linear generalization of principal component analysis (PCA), unsupervised clustering, and tSNE visualization for unbiased selection of circulating EC (Fig 1). Paired analysis revealed that the number of circulating EC increased 2.6 [0.5-5] fold at the third day after transplantation, recovering to preoperative levels at day 7 post-transplant (Fig 2a). Patients who had a biopsy proven acute rejection and recorded a higher amount of circulating EC in comparison to the previous measured time-point, showed a significant (2-fold) increase in the MFI for the damage marker KIM-1 (p

Autoantibody production significantly decreased with APRIL/BLyS blockade in murine chronic rejection kidney transplant model.

Chronic antibody mediated rejection (cAMR) remains a significant barrier to achieving long-term graft survival in kidney transplantation, which results from alloantibody production from B lymphocytes and plasma cells. APRIL (A proliferation-inducing ligand) and BLyS (B lymphocyte stimulator) are critical survival factors for B lymphocytes and plasma cells. Here we describe the results of APRIL/BLyS blockade in a murine cAMR kidney transplant model. c57/B6 mice underwent kidney transplantation with Bm12 kidneys (minor MHC mismatch), a well-described model for chronic rejection where animals cannot make donor specific antibody but rather make antinuclear antibody (ANA). Following transplantation, animals received TACI-Ig (to block APRIL and BLyS) or no treatment. Animals were continued on treatment until harvest 4 weeks following transplant. Serum was analyzed for circulating anti-nuclear autoantibodies using HEp-2 indirect immunofluorescence. Spleen and transplanted kidneys were analyzed via H&E. ANA production was significantly decreased in APRIL/BLyS blockade treated animals (p<0.0001). No significant difference in autoantibody production was found between syngeneic transplant control (B6 to B6) and APRIL/BLyS blockade treated animals (p = 0.90). Additionally, disruption of splenic germinal center architecture was noted in the APRIL/BLyS blockade treated animals. Despite the significant decrease in autoantibody production and germinal center disruption, no significant difference in lymphocyte infiltration was noted in the transplanted kidney. APRIL/BLyS blockade resulted in a significant decrease of autoantibody production and disrupted splenic germinal center formation in a chronic kidney transplant model, however in this model no difference in kidney transplant pathology was seen, which may have to do with the absence of any T cell centric immunosuppression. Regardless, these findings suggest that APRIL/BLyS blockade may play a role in decreasing antibody formation long-term in kidney transplantation. Future investigations will use APRIL/BLyS blockade in conjunction with T lymphocyte depleting agents to determine its efficacy in chronic rejection.

P056 Cellular crossmatch (CXM) by flowspot predicts cellular rejection in kidney transplantation

Aim To evaluate newly developed CXM assay in prediction of cellular rejection of kidney transplantation. Methods: CXM: Irradiated auto or donor PBMC were co-incubated with recipient PBMC and Th1 (IFNγ, IL-2) and Th2 (IL-4, IL-5, IL-10) cytokine capture beads for overnight. After cell lysis, the captured cytokines on each bead were detected by PE-labeled 2nd antibody on a flow cytometer. The percentage of positive beads (Flowspot %) were counted which proportionately correlated with numbers of donor specific responding cells. The MFI level correlated with the cytokine secretion capability of responding cells. DSA-FXM: Stanford method; Standard methods: T/B cell FXM, Luminex IgG/C1q SAB. Results PBMC from two cellular rejection kidney transplantation clinical cases were tested by CXM Flowspot assay. Case 1 LMX IgG/C1q DSA was negative in pre-14 days patient serum. T/B FXM results showed auto positive and allo positive and DSA FXM also detected auto- and allo- CI and CII DSA in the same serum. Patient had cellular rejection on 19th day after kidney transplantation (Tx), proved by biopsy (ACR 1B-2). The retrospective CXM on patient PBMC (14 days before transplantation) showed that the recipient had increased secretion of IFNγ and IL-2 to donor cells. De novo LMX-IgG DSA B44, B57, DQ6, DP3 (MFI: 948–2512) were found in post-11 and 18 days sera; and LMX-C1q DSA B44, B57, DQ6 (MFI: 2302–11551) in post-18 days serum. Case 2 LMX-IgG detected possible DR52 (MFI: 816) DSA but none complement fixing antibody in pre-8 days serum. T/B FXM results were negative and no DSA was detected by DSA-FXM in the same sample. However, patient got cellular rejection post-transplantation (ACR 1A). The retrospective CXM by Flowspot on patient PBMC (pre-43 days) showed strong donor specific IFNγ and IL-2 secretions. Conclusions CXM by Flowspot is able to detect donor specific immunity in recipient. It potentially can be used to predict cellular rejection in kidney transplantation. Download : Download high-res image (292KB) Download : Download full-size image

Complement markers in immunoadsorption combined with membrane filtration for antibody-mediated rejection kidney transplantation

Complement markers in immunoadsorption combined with membrane filtration for antibody-mediated rejection kidney transplantation

A Pharmacometric Approach to Support a Treatment Effect of Everolimus in Liver Transplantation.

A novel analytic approach was developed to support a quantitative assessment of treatment effect of everolimus (EVR) when combined with reduced tacrolimus (rdTAC) in the prevention of rejection in liver transplantation, when challenged to interpret results from a noninferiority (NI) trial using a standard tacrolimus (sdTAC) active control regimen. Method: The unique design of a clinical trial intended to evaluate efficacy of EVR used with rdTAC in prevention of rejection in liver transplantation (LTx), involving randomization to study treatment at 30 days post transplant, to minimize risk of hepatic artery thrombosis, hindered assessment of an EVR treatment effect that would be greater than a placebo's. Although the trial design was based on a prespecified NI margin of 12% for the primary efficacy endpoint (treated biopsy proven acute rejection, graft loss or death), no external information from other clinical trials could be found to justify a NI margin, and lack of such a justification precluded interpretation of the efficacy results. [1] A “totality of information” approach was applied using observed data from this trial to derive a NI margin based on a novel pharmacometric method, and considering the mechanisms of action of everolimus, tacrolimus and steroids at different steps of lymphocyte activation, relevant literature reports of everolimus in Ltx,and efficacy of everolimus in prevention of rejection kidney transplantation (KTx). Results: A new NI margin derived from the exposure-response relationship for TAC, based on efficacy data from the sTAC control arm, smaller than 12%, allowed interpretation of observed results, supporting contribution of everolimus greater than expected from placebo + rTAC exposure, relative to the sTAC target exposure. This finding was considered consistent with mechanisms of action for everolimus and tacrolimus in a three-signal model of T-cell activation. Results from literature reports were supportive of everolimus activity in Ltx as was efficacy of everolimus for KTx. Conclusion: The findings from this “totality of information” approach supported by exposure-response analyses contributed favorably to assessment of the overall risk/benefit profile of everolimus in a regimen with reduced tacrolimus exposure, in the indication of prophylaxis of rejection in liver transplantation. [1] Guidance for Industry Non-Inferiority Clinical Trials: http://http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM202140.pdf

From Humans to Experimental Models: The Cytoprotective Role of Clusterin in the Kidney

Clusterin (CLU) is a chaperone-like protein and has been discovered more than thirty years ago; however, its biological significance is still not fully understood. This review aims to summarize the principal observations of CLU roles related to the kidney. In humans, three or more mRNA isoforms of CLU could be expressed due to different translation start sites, but only two forms of CLU protein, secreted (sCLU, isoform 2) and nuclear (nCLU, isoform 1), have been well characterized, whereas there is only sCLU form in mice. In the biopsies of renal tissue from patients, up regulated CLU expression has been found in rejecting kidney transplants or diseased kidneys, and a lower level of serum CLU is correlated with many types of kidney disease in patients. In mice, a deficiency in CLU expression specifically leads to the phenotype of age-dependent chronic glomerular injury - moderate to severe accumulation of the mesangial matrix, becomes more susceptible to ischemia-reperfusion injury (IRI), negatively impacts renal repair after IRI and worsens renal fibrosis after ureteral obstruction. All these observations may imply the biological significance of CLU for the maintenance of the tissue homeostasis in adult kidneys. However, how CLU protects the kidney from injury or by which extracellular and intracellular pathways mediate the cyto-protection of CLU in the kidney has not been well investigated. Understanding of the cyto-protective activities of CLU in the kidney could lead to the development of novel therapeutic strategies for the prevention and/or treatment of kidney injury or diseases.

A Shift towards Pro-Inflammatory CD16+ Monocyte Subsets with Preserved Cytokine Production Potential after Kidney Transplantation

BackgroundThe presence of monocyte-macrophage lineage cells in rejecting kidney transplants is associated with worse graft outcome. At present, it is still unclear how the monocyte-macrophage related responses develop after transplantation. Here, we studied the dynamics, phenotypic and functional characteristics of circulating monocytes during the first 6 months after transplantation and aimed to establish the differences between kidney transplant recipients and healthy individuals.MethodsPhenotype, activation status and cytokine production capacity of classical (CD14++CD16−), intermediate (CD14++CD16+) and non-classical (CD14+CD16++), monocytes were determined by flow cytometry in a cohort of 33 healthy individuals, 30 renal transplant recipients at transplantation, 19 recipients at 3 months and 16 recipients at 6 months after transplantation using a cross-sectional approach.ResultsThe percentage of both CD16+ monocyte subsets was significantly increased in transplant recipients compared to healthy individuals, indicative of triggered innate immunity (p≤0.039). Enhanced production capacity of tumor necrosis factor-α, interferon-γ and interleukin-1β was observed by monocytes at transplantation compared to healthy individuals. Remarkably, three months post-transplant, in presence of potent immunosuppressive drugs and despite improved kidney function, interferon-γ, tumor necrosis factor-α and interleukin-10 production capacity still remained significantly increased.ConclusionOur data demonstrate a skewed balance towards pro-inflammatory CD16+ monocytes that is present at the time of transplantation and retained for at least 6 months after transplantation. This shift could be one of the important drivers of early post-transplant cellular immunity.

Detection of antibodies against HLA-C epitopes in patients with rejected kidney transplants

Background Although HLA-C matching is not considered in kidney transplantation, several reports have shown that anti-HLA-C antibodies are associated with rejection and graft failure. DNA-based typing methods can now accurately determine HLA-C compatibility and sensitive assays such as Luminex with single alleles can identify HLA-C antibodies. HLA-C displays considerable amino acid polymorphism that can be translated into a structurally defined epitope repertoire. Methods We have analyzed post-allograft nephrectomy sera from 45 HLA-C mismatched cases submitted by 15 laboratories worldwide participating in the 15th International Histocompatibility Workshop. All of them had HLA class I antibodies detected by a Luminex-based solid phase method using single-allele beads. This study addressed the determination of antibodies against donor HLA-C mismatches. Analysis of antibody reactivity patterns was performed using HLAMatchmaker, a structurally based matching program that considers 56 HLA-C eplets to define antibody-reactive epitopes. Many eplets shared by groups of HLA-C antigens, whereas others are also shared with HLA-A and/or HLA-B antigens. Results Twenty-seven patients (60%) had donor-specific HLA-C antibodies, significantly less than the donor-specific antibodies induced by HLA-A and HLA-B mismatches. HLA-C antibody responses correlated with the eplet loads of the HLA-C mismatches. There were 352 instances whereby a donor HLA-C eplet was mismatched and for 84 (24%) of them there was antibody reactivity with a particular eplet (69 instances) or an eplet pair (15 instances). The latter generally consisted of mismatched eplets paired with self-eplets shared between the immunizing HLA-C alleles and HLA alleles of the patient. Several HLA-C eplets exhibited a relatively high immunogenicity as evidenced by their frequencies of specific antibodies. Conclusion These findings demonstrate the importance of HLA-C mismatching in humoral sensitization and that HLA-C epitopes can induce specific antibodies. They illustrate the usefulness of HLAMatchmaker in understanding donor-specific antibody reactivity patterns and the determination of HLA mismatch acceptability when transplantation is considered.

Why can sensitization by an HLA-DR2 mismatch lead to antibodies that react also with HLA-DR1?

HLAMatchmaker is a matching algorithm that can be used to characterize antibodies specific for structurally defined epitopes. Under the auspices of the 15 th International Histocompatibility Workshop, we are conducting a multilaboratory collaborative project to characterize these epitopes and also to determine how often they induce specific antibodies in patients with rejected kidney transplants. This report addresses the reactivity of post-allograft nephrectomy sera tested for DRB antibodies with Luminex assays using single alleles. This analysis was performed for 19 informative kidney transplant cases contributed by 13 laboratories worldwide. There were 11 cases with a single DR2 mismatch (DR15 or DR16), and nine of them (82%) showed antibodies with both DR2 and DR1. Although these antigens might share an epitope recognized by these antibodies, this interpretation is incorrect. The HLAMatchmaker analysis offers a clearly different explanation that involves antibodies induced by DR51, which commonly associates with DR2. DR51 has an epitope defined by the 96EV eplet, which is also present on DR1 but no other DR antigen. This means that the reactivity with DR51 and DR1 reflects the presence of 96EV-specific antibodies. Conversely, we analyzed eight patients sensitized by a single DR1 mismatch that has no associated DR51. All of these patients reacted also with DR51, and this could be explained only by antibodies against the shared 96EV eplet. These findings demonstrate that 96EV represents a highly immunogenic epitope that can induce cross-sensitization between antigens encoded by the different DRB loci, and also that DR51 is important in determining DRB mismatch acceptability of potential donors. This analysis has also demonstrated that antibody responses are restricted to a few epitopes on these immunizing DR antigens. For DR2 they are 142M3 (unique for DR2), 71QAA (shared with DB5*02), and 96QV (shared with DR10). DR51 mismatches appear to have three immunogenic eplets: 96EV (shared with DR1), 108T3 (unique for DR51), and 40HFD (shared with DR9). Immunogenic eplets on DR1 are 12LKF2 (unique for DR1), 14FEH (shared with DR9 and DR10), and 25HRL (shared with DR10).

PP4-015 MICA and MICB antibodies in patients who rejected kidney transplants

PP4-015 MICA and MICB antibodies in patients who rejected kidney transplants

Mica and micb antibodies in patients who rejected kidney transplants

Mica and micb antibodies in patients who rejected kidney transplants

The kidney as a second site of human C-reactive protein formation in vivo.

C-reactive protein (CRP) is the main acute phase reactant in humans. Its production is presumably restricted to the liver but extrahepatic expression by inflamed tissue has not been studied in detail. By real-time PCR and immunohistochemistry we here show that renal cortical tubular epithelial cells (TEC) express CRP mRNA and protein within 6 h after stimulation with conditioned medium (CM) or IL-6, but not IL-1alpha or TNF-alpha. Western blot analysis with monoclonal anti-CRP antibody that recognizes native CRP revealed protein secretion into supernatants of CM-stimulated TEC cultures. While hepatoma-derived Hep3B cells could be induced similarly, peripheral blood mononuclear cells could not. CRP mRNA transcripts were observed in nephrectomized renal allografts with severe acute rejection but not with chronic allograft nephropathy (CAN). Of 19 needle biopsies of acutely rejecting kidney transplants, 15 demonstrated CRP mRNA production with the relative expression levels increasing with the severity of rejection. On the other hand, none of 7 graft biopsies with acute tubular necrosis (ATN) or CAN showed CRP mRNA expression. By using monoclonal anti-CRP antibody, cortical tubules as well as glomerular cells were shown to locally express CRP in rejecting, but not in ATN kidneys. We conclude that inflamed kidneys represent a so far unknown site of CRP formation in vivo. These data shed new light on the acute phase reaction not merely representing a systemic inflammatory pathway but probably being part of the local immune response.

Transcription factor IRF-1 in kidney transplants mediates resistance to graft necrosis during rejection.

In many circumstances kidney transplants remain viable despite extensive inflammation, permitting rejection episodes to be reversed. The mechanisms by which the kidney resists host effector mechanisms are not known. In mouse kidney transplants, resistance requires interferon-gamma (IFN-gamma), which acts on the graft to protect the graft from necrosis during the first days of rejection as well as inducing major histocompatibility complex (MHC) expression. Because some effects of IFN-gamma are mediated by transcription factor IRF-1, the role of IRF-1 in the donor tissue early phases of rejection of mouse kidney allografts was studied. H-2(b) kidneys were transplanted from mice with wild-type IRF-1 genes (WT) or mice with disrupted IRF-1 genes (IRF-1KO) into CBA (H-2(k)) recipients. At day 5 and day 7, IRF-1KO and WT kidneys were functioning despite typical rejection pathology: interstitial infiltration and tubulitis. However, function deteriorated rapidly in rejecting IRF-1KO allografts, associated with widespread epithelial necrosis, peritubular capillary congestion, glomerulitis, and fibrin thrombi in small veins by day 7. At day 21, WT kidneys were viable despite severe tubulitis and arteritis, whereas IRF-1KO kidneys showed massive necrosis of the epithelium despite patent large vessels. Compared with WT kidneys, rejecting IRF-1KO kidneys showed less induction of donor MHC yet had similar mRNA levels of perforin, granzyme B, and Fas ligand and evoked host alloantibody responses. Thus in rejecting kidney transplants, IRF-1 in the graft mediates MHC induction, but it also mediates resistance to necrosis, an effect that could be crucial to permit success in interventions against rejection.

Modelling Time-Dependent Interaction in a Time-Varying Covariate and Its Application to Rejection Episodes and Kidney Transplant Failure

Acute rejection episodes are thought to be prognostic of eventual kidney graft failure. The influence of rejection events on the hazard of transplant failure appears to be a complex function of how long after transplantation the rejection event occurs as well as the time elapsed since the rejection event. To examine the nature of this relationship, we propose a penalized likelihood approach to estimate the parameters of a two-dimensional rectanglewise constant hazard model. The approach appears to be fairly successful at modelling time dependency in a time-varying covariate. The approach is equally applicable for modelling fixed covariates that act in a jointly nonproportional (non-log-linear) and time-dependent manner.

Macrophages and HLA‐DR(+) cells in acutely rejecting kidney transplants, predict subsequent graft survival, even after reversal of the acute episode

Renal graft biopsies from 19 selected patients with acute cellular rejection (ACR) were analysed using a panel of monoclonal antibodies. All patients had only one episode of ACR, which was completely reversible. In 11 patients (group 1) graft function slowly deteriorated over a period of 14 (±17) months after the episode. In the remaining eight (group 2) graft function remained stable over a similar period of observation. In group 1 there was a significantly increased inflitrate of glomerular and interstitial monocytes/macrophages (MM) when compared with group 2. Also, the expression of HLA‐DR antigen by the tubular cells were stronger in group 1, while T‐cells in the glomeruli and the interstitium were equally distributed in both groups. We conclude that large numbers of MM and HLA‐DR expressing cells (glomerular, interstitial and tubular) in rejecting kidneys predict a more rapid decline of follow‐up renal function despite reversal of the acute episode. This may suggest that subclinical ongoing injury continues in some patients and perhaps more intense immunosuppression is necessary to prevent graft loss.

Macrophages and HLA‐DR(+) cells in acutely rejecting kidney transplants, predict subsequent graft survival, even after reversal of the acute episode

SUMMARY: Renal graft biopsies from 19 selected patients with acute cellular rejection (ACR) were analysed using a panel of monoclonal antibodies. All patients had only one episode of ACR, which was completely reversible. In 11 patients (group 1) graft function slowly deteriorated over a period of 14 (± 17) months after the episode. In the remaining eight (group 2) graft function remained stable over a similar period of observation. In group 1 there was a significantly increased inflitrate of glomerular and interstitial monocytes/macrophages (MM) when compared with group 2. Also, the expression of HLA‐DR antigen by the tubular cells were stronger in group 1, while T‐cells in the glomeruli and the interstitium were equally distributed in both groups. We conclude that large numbers of MM and HLA‐DR expressing cells (glomerular, interstitial and tubular) in rejecting kidneys predict a more rapid decline of follow‐up renal function despite reversal of the acute episode. This may suggest that subclinical ongoing injury continues in some patients and perhaps more intense immunosuppression is necessary to prevent graft loss.