Functional Activity of the Complement System in Deceased Donors in Relation to Kidney Allograft Outcome

Complement activation is considered one of the mediators of renal ischemia-reperfusion injury. Elevated levels of C5b-9, C3a, and C5a are detected in sera of deceased kidney donors. The goal of the study was to characterize the functional activity of complement pathways in donor sera and to assess their influence on transplant outcome.

MATERIALS AND METHODS

Sixty-four deceased kidney donors (age 45 ± 16 years; 28 female, 36 male) and 27 healthy controls (age 42 ± 12 years; 14 female, 13 male) were enrolled in the study. The results of transplantation for the respective 122 kidney recipients were included in the analysis. The functional activities of classical (CP), lectin (LP), and alternative (AP) pathways were measured using Wielisa-kit (reference normal level = 100%). In most cases, decreased functional activity reflects the activation status of the pathway.

RESULTS

The median (interquartile range) functional activities of the pathways in donor sera were CP 118 (89-150)%, LP 80 (20-127)%, and AP 74 (50-89)%, and did not differ from the control values CP 110 (102-115)%, LP 81 (26-106)%, AP 76 (61-88)%. The frequency of pathway activation observed in controls was CP 0%, LP 11%, and AP 0%. Deceased donors did not differ in activation of classical (11%) and lectin (13%) pathways, but presented a higher rate of alternative pathway activation (19%, P = .03). No significant influence of any pathway functional activity or its activation was proved to influence the transplant outcome.

CONCLUSION

Complement activation via alternative pathway was observed in diseased donor sera. No predictive potential of donor complement functional activity on the transplant outcome could be proved.

Histopathological Relevance of Angiotensin II Type 1 Receptor in Renal Transplant Biopsy

The occurrence of anti-angiotensin II type 1 receptor (AT1R) antibodies is thought to be a risk factor for transplant injury, but the relationship of AT1R to graft loss in renal transplantation has not been assessed. The aim of our study was to evaluate the expression of AT1R and its relationship with graft loss in patients who had a renal transplant biopsy for cause.

METHODS

AT1R immunoreactivity was analyzed in 170 renal transplant biopsies. Immunohistochemical evaluation of AT1R expression was performed on 4 μm-thick paraffin sections mounted on silanized slides. AT1R expression was analyzed in 5 compartments: 1. glomeruli, 2. renal blood vessels (small and intermediate arteries), 3. peritubular capillaries, 4. tubular epithelium, and 5. interstitium based on a 3-step scale.

RESULTS

Initially we checked 170 consecutive samples of biopsies for the immunoreactivity of the AT1R. The study finally included 118 renal transplant patients in 1-year observation after the biopsy. The renal allograft biopsy was performed between 6 days and 24 years after transplantation and the diagnosis was based on Banff criteria. We observed positive immunostaining of AT1R in tubular epithelium in 26.3% (42/118) of patients. A total of 7 patients had staining assessed as 2 and 35 as 1. One year post-biopsy graft loss in the AT1R (+) patients was 35.7 % (15/42) compared to 14.5% (11/76) in the AT1R (-) group (P = .008).

CONCLUSIONS

The expression of AT1R in tubular epithelium of the biopsy for cause was associated with significantly higher graft loss. The relevance of AT1R should be considered for better transplant immunological risk assessment.

Endothelin A Receptors Expressed in Renal Blood Vessels of Renal Transplant Patients Are Connected With Acute Tubular Necrosis or Antibody-Mediated Rejection

BACKGROUND

The role of non-HLA antibodies named antiendothelin A receptor antibodies is potentially significant but not established. The significance of the endothelin A receptor (ETAR) and its expression in renal biopsy has not been defined. We decided to evaluate the presence and relevance of ETARs in renal transplant biopsy for cause. The aim of our study was to evaluate the immunoreactivity of the ETAR and its significance in patients who had a renal transplant biopsy due to deterioration of transplant function (biopsy for cause) with detailed characterization of staining in small and intermediate arteries of renal transplant biopsies.

METHODS

Immunohistochemical expression of ETARs was analyzed in 162 renal transplant biopsies. Microscopic evaluation of ETAR expression (polyclonal antibody) was performed on paraffin sections. ETAR expression was analyzed in renal blood vessels (small and intermediate arteries) based on three-step scale.

RESULTS

We analyzed 154 patients who had renal allograft biopsy between 6 days and 24 years (median 597 days) after transplantation. Positive staining of ETAR in small and intermediate arteries was noticed in 9 patients. Among these patients, 4 had early biopsies (<3 months after transplantation), all developed acute tubular necrosis, and 1 developed additionally acute humoral rejection. Further, 4 patients had late biopsy (1-8 years after transplantation) and all developed characteristics of antibody mediated rejection. Lastly, 1 patient had no characteristic changes in the biopsy 4 months after transplantation. Graft loss 1 year after biopsy was higher in patients who were ETAR-positive but statistical significance was not achieved.

CONCLUSIONS

The expression of endothelin receptors in renal blood vessels (small and intermediate arteries) seems to be important in diagnosis of damage during acute tubular necrosis and antibody-mediated rejection.

B Cell Activating Factor (BAFF) in Long-term Kidney Transplant Recipients Is Not a Prognostic Marker for Allograft Dysfunction or Survival

OBJECTIVE

B cell activating factor (BAFF) has been shown to play a role in B cell survival, maturation, and activation, and has been linked with renal transplant outcome. BAFF signaling has been associated with plasmablast survival, anti-HLA immunization, and loss of graft function. We aimed to analyze the interplay between BAFF, memory B cells, and plasmablasts in relation to allograft function in long-term kidney transplant (KTx) recipients and their anti-HLA sensitization.

MATERIALS AND METHODS

This study included 70 long-term KTx recipients on standard immunosuppression 15 ± 6 years post transplantation (44 stable, 26 chronic allograft dysfunction, CAD) and 25 healthy volunteers. CD19+ B cells, memory B cells (CD19+CD27+), and plasmablasts (CD19+CD24-CD27++CD38++) were enumerated with flow cytometry. BAFF serum level and anti-HLA antibodies were assessed by Luminex bead arrays.

RESULTS

We found no difference in BAFF levels between KTx recipients and controls (median, interquartile range: 1.67, 1.40-1.97 vs 1.78, 1.63-1.93 ng/mL, P = .478) and no correlation between BAFF level and cell counts. Recipients presented lower plasmablast count than controls (22.5, 8-57 vs 79, 48-166 cells/mL, P < .001). There was a positive correlation between estimated glomerular filtration rate and plasmablasts (r_s = 0.30, P = .013) in recipients. Cell populations and BAFF were not related to the presence of anti-HLA antibodies. None of the parameters investigated was related to deterioration of allograft function during the 2-year follow-up.

CONCLUSION

BAFF serum level is not related to anti-HLA sensitization, circulating memory B cells, plasmablast count, or allograft function. Circulating plasmablasts are associated with current allograft function but are not prognostic for future course.

Pretransplant Immune Interplay Between Donor and Recipient Influences Posttransplant Kidney Allograft Function

BACKGROUND

Renal transplant candidates present immune dysregulation caused by chronic uremia, and deceased kidney donors present immune activation induced by brain death. Pretransplant donor and recipient immune-related gene expression were examined in the search for novel predictive biomarkers crosslinking recipient and donor pretransplant immune status with transplant outcome.

MATERIALS AND METHODS

This study included 33 low-risk consecutive renal transplant recipients and matched deceased donors. The expression of 29 genes linked to tissue injury, T-cell activation, cell migration, and apoptosis were assessed in postreperfusion kidney biopsies, as well as 14 genes in pretransplant peripheral blood of the kidney recipients. Gene expression was analyzed with real-time polymerase chain reaction on custom-designed low-density arrays.

RESULTS

Donor MMP9 expression was related to delayed graft function occurrence (P = .036) and short term kidney allograft function (14th day r_s = -0.44, P = .012; 1st month r_s = -0.46, P = .013). Donor TGFB1 expression was associated with short- and long-term graft function (14th day r_s = -0.47, P = .007; 3rd month r_s = -0.63, P = .001; 6th month r_s = -0.52, P = .010; 12th month r_s = -0.45, P = .028; 24th month r_s = -0.64, P = .003). Donor TGFB1 expression was not related to donor age (r_s = 0.32, P = .081), which was also an independent factor influencing the outcome. Recipient gene expression was not related to graft function but determined the acute rejection risk. Recipient IFNG and, to a lesser extent, IL18 expression were protective against acute rejection (area under the curve [AUC] 0.84, P < .001, and AUC 0.79, P < .001, respectively).

CONCLUSION

Kidney transplant outcome depends on the interplay between donor-related immune factors, which mostly affect allograft function and recipient immune milieu, influencing an alloreactive response.

Increased plasma matrix metalloproteinase-2 (MMP-2), tissue inhibitor of proteinase-1 (TIMP-1), TIMP-2, and urine MMP-2 concentrations correlate with proteinuria in renal transplant recipients

BACKGROUND

The most frequent cause of kidney allograft loss is chronic allograft injury, often with proteinuria as the clinical feature. Occurrence of proteinuria late after kidney transplantation is associated with worse graft function and patient survival.

AIM

The aim of the study was to assess plasma and urine matrix metalloproteinases (MMP-2 and MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) in proteinuric renal transplant recipients (RTRs). The factors were determined by enzyme-linked immunosorbent assay in 150 RTRs (51 women and 99 men), aged 49.2 ± 11.5 years, at mean 73.4 ± 41.2 months after kidney transplantation (range: 12 to 240 months).

RESULTS

Proteinuric RTRs compared with non-proteinuric RTRs had higher median plasma MMP-2 (P = .012), TIMP-1 (P = .0003), and TIMP-2 (P = .0021) concentrations, as well as higher urine MMP-2 (P < .0001) excretion. The presence of proteinuria had no impact on plasma MMP-9 and urine MMP-9, TIMP-1, and TIMP-2. Proteinuria and estimated daily proteinuria (uPr:uCr) correlated positively with plasma MMP-2 (rs = 0.226, P = .0054 and rs = 0.241, P = .003), TIMP-1 (rs = 0.305, P = .00015 and rs = 0.323, P = .000055), TIMP-2 (rs = 0.273, P = .0007 and rs = 0.269, P = .001) and urine MMP-2 (rs = 0.464, P < .0001 and rs = 0.487, P < .0001), respectively. Proteinuric RTRs had impaired graft function with higher median serum creatinine concentrations (1.91 [1.60-2.43] mg/dL versus 1.41 [1.20-1.65] mg/dL, P < .00001) and lower estimated glomerular filtration rate (36 [28-45] mL/min/1.73 m(2) versus 53 [43-61] mL/min/1.73 m(2), P < .00001) than RTRs without proteinuria.

CONCLUSIONS

Our research revealed that in RTRs, proteinuria was significantly associated with increased concentrations of enzymes involved in extracellular matrix (ECM) degradation: plasma MMP-2, TIMP-1, TIMP-2, and urine MMP-2. Findings strongly emphasize increased plasma TIMPs in proteinuric RTRs that inhibit degradation of ECM by MMPs and favor excessive deposition of ECM proteins.

Advanced age of renal transplant recipients correlates with increased plasma concentrations of interleukin-6, chemokine ligand 2 (CCL2), and matrix metalloproteinase 2, and urine concentrations of CCL2 and tissue inhibitor of metalloproteinase 1

BACKGROUND

Advanced age of renal transplant recipients (RTRs) has a negative impact on kidney allograft survival through impaired extracellular matrix degradation by the matrix metalloproteinases/tissue inhibitors of metalloproteinases (MMPs/TIMPs) system. Moreover, older RTRs are at risk of smoldering inflammation, known as inflammaging.

AIM

The aim of the study was to assess the impact of a RTR's age on plasma and urine concentrations of interleukin 6 (IL-6), chemokine ligand 2 (CCL2), and the MMPs/TIMPs system.

MATERIAL AND METHODS

One hundred fifty adult RTRs (8.7% ≥ 65 years) and 37 adult healthy volunteers (10.8% ≥ 65 years) were enrolled in the study. The studied factors (IL-6, CCL2, MMP-2, MMP-9, TIMP-1 and TIMP-2) were quantified in plasma and urine with enzyme-linked immunosorbent assay. The Mann-Whitney U test and Spearman's (rs) rank correlation were applied, and differences with a P < .05 were considered statistically significant.

RESULTS

There was a weak but significant positive correlation between increasing RTR's age and plasma IL-6 (rs = 0.18, P = .028), CCL2 (rs = 0.27, P = .001), and MMP-2 (rs = 0.20, P = .017), as well as urine CCL2 (rs = 0.16, P = 0.050) and TIMP-1 (rs = 0.20, P = .014) concentrations.

CONCLUSIONS

Advancing age of RTRs correlates with increasing plasma IL-6 and CCL2 concentrations, reflecting smoldering inflammation (known as inflammaging) and alterations in MMPs/TIMPs profiles, especially with increased plasma MMP-2 and urine TIMP-1 concentrations.

Pathogenic role of antibodies against monomeric C-reactive protein in tubulointerstitial nephritis and uveitis syndrome

Antibodies against monomeric C-reactive protein, which is a target antigen expressed both in kidney tubules and uveal cells, have been recently detected in patients with active tubulointerstitial nephritis and uveitis syndrome. We report the case of an 65-year-old woman with acute renal failure caused by biopsy-proven tubulointerstitial nephritis and the onset of uveitis 21 months later. The expression of monomeric C-reactive protein in kidney oligobiopsy was confirmed by immunohistochemical staining using mouse monoclonal antibody against human monomeric C-reactive protein. The levels of antibodies against monomeric C-reactive protein were 117% of the reference during the flare and 22% during the remission of the disease. The difference in the levels of antibodies against monomeric C-reactive protein during flare and remission, and above all positive biopsy staining, supports their pathogenic role in this disease.

The impact of de novo donor-specific anti-human leukocyte antigen antibodies on 5-year renal transplant outcome

Numerous studies have shown that circulating donor-specific antibodies targeting human leukocyte antigen (HLA) are associated with accelerated renal transplant failure, but many patients with these antibodies have good graft function. The aim of our study was to investigate the long-term graft function and survival in patients with de novo post-transplant donor-specific anti-HLA antibodies (DSA). Our prospective study included 78 consecutive recipients with a negative crossmatch before transplantation. Recipient serum samples were assayed for DSA in week 2 and 1, 3, 6, 9, 12 months after transplantation using a complement-dependent lymphocytotoxic technique with donor lymphocytes. Additionally, patients with DSA and stable renal function in the first year were tested with a more sensitive flow-panel-reactive antibody. DSA were present in 34 (44%) of our patients during the first 12 months after transplantation. Biopsy-proved acute rejection occurred in 11 DSA-positive and 10 DSA-negative patients. Seven DSA-positive patients had antibody-mediated rejection and no DSA-negative ones developed humoral rejection. The serum creatinine level in DSA-positive patients was significantly higher (2.48 vs 1.43 mg/dL) in year 5. The 13 (38%) DSA-positive patients with good graft function in month 12 were stable during a 5-year follow-up: their serum creatinine was 1.46 ± 0.4 in year 1 and 1.56 ± 0.4 mg/dL in year 5 and nobody lost their allograft. One- and 5- year graft survivals were appropriately 85% and 59% in DSA-positive patients compared to 93% and 93% in DSA-negative patients. To sum up, post-transplant DSA had a significant influence on kidney function and graft survival but in 38% of patients the presence of DSA did not decrease a 5-year renal function. A good renal allograft function in the presence of DSA in the first year after transplantation and cessation of their production in the subsequent years may be a good prognostic marker for a long-term allograft function and survival.

Increased plasma tissue inhibitors of metalloproteinase concentrations as negative predictors associated with deterioration of kidney allograft function upon long-term observation

Chronic allograft injury (CAI) is the most frequent cause of progressive kidney allograft impairment and eventual loss, which is due to interstitial fibrosis and tubular atrophy (IF/TA). Mechanisms of CAI are not fully understood. Chemokines, cytokines, metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs) play roles in fibrosis development. The aims of this study were to evaluate plasma and urine TIMPs (TIMP-1 and TIMP-2), MMPs (MMP-2 and MMP-9), proinflammatory interleukin-6 (IL-6), chemokine (C-C motif) ligand 2 (CCL2 chemokines previously known as monocyte chemoattractant protein-1 [MCP-1]) among 150 recipients beyond 1 year post-renal transplantations and to explore the usefulness of these potential biomarkers of ongoing allograft injury. Renal transplant recipients compared with healthy volunteers (control group) showed significantly increased plasma and urine IL-6, MMP-9, TIMP-1, and TIMP-2, as well as lower plasma MMP-2 and urine CCL2 concentrations. Compared with recipients showing good function those with impairments displayed higher plasma TIMP-1 (P < .001) and TIMP-2 (P = .003) concentrations. The recipient estimated glomerular filtration rate (eGFR) values negatively correlated with plasma TIMP-1 and TIMP-2 levels (r = -0.43; P < .0001 and rs = -0.42; P < .0001, respectively) and with urine IL-6 excretion (rs = -0.33; P < .0001). Multivariate and receiver operating characteristic (ROC) analyses showed TIMP-1 plasma level assessments to be useful estimates of allograft injury.

Kidney ischemic injury genes expressed after donor brain death are predictive for the outcome of kidney transplantation

The results of deceased donor kidney transplantation largely depend on the extent of organ injury induced by brain death and the transplantation procedure. In this study, we analyzed the preprocurement intragraft expression of 29 genes involved in apoptosis, tissue injury, immune cell migration, and activation. We also assessed their influence on allograft function. Before flushing with cold solution we obtained 50 kidney core biopsies of deceased donor kidneys immediately after organ retrieval. The control group included 18 biopsies obtained from living donors. Gene expression was analyzed with low-density arrays (Taqman). LCN2/lipocalin-2 is considered a biomarker of kidney epithelial ischemic injury with a renoprotective function. HAVCR1/KIM-1 is associated with acute tubular injury. Comparison of deceased donor kidneys to control organs revealed a significantly higher expression of LCN2 (8.0-fold P=.0006) and HAVCR1 (4.7-fold, P<.0001). Their expressions positively correlated with serum creatinine concentrations after 6 months after transplantation: LCN2 (r=.65, P<.0001), HAVCR1 (r=.44, P=.006). Kidneys displaying delayed graft function and/or an acute rejection episode in the first 6 months after showed higher LCN2 expression compared to event-free ones (1.7-fold, P=.027). A significantly higher increase in expression of TLR2 (5.2-fold), Interleukin (IL) 18 (4.6-fold), HMGB1 (4.1-fold), GUSB (2.4-fold), CASP3 (2.0-fold) FAS (1.8-fold), and TP53 (1.6-fold) was observed among deceased donor kidneys compared with the control group. Their expression levels were not related to clinical outcomes: however, they showed significant correlations with one another (r>.6, P<.0001). We also observed a slightly reduced expression of IL10 (0.6-fold, P=.004). Our data suggested that increased LCN2 and HAVCR1 expression observed in the kidneys after donor brain death were hallmarks of the organ injury process. LCN2 expression level in retrieved kidneys can predict kidney transplantation outcomes.