Kidney graft failure and presensitization against HLA class I and class II antigens

Superiority of Single-Antigen Bead Study in Donor-Specific Antibodies: Determination in Highly Sensitized Patients

OBJECTIVES

The presence of donor-specific antibodies against HLA before kidney transplant has been variably associated with decreased long-term graft survival. Data on the association between pretransplant donor-specific antibodies and rejection and cause of graft failure in recipients of donor kidneys are scarce.

MATERIALS AND METHODS

For this study of HLA antibody levels, we analyzed serum samples from 76 patients (48 women and 28 men) who were prepared for kidney transplant at the Baskent University İstanbul Hospital between 2017 and 2022. Levels were determined by using Lifecodes panel reactive antibody class I and II identification kits and Lifecodes LSA class I and II identification kits by the Luminex assay method.

RESULTS

Multiple antigen tests showed more than 70% sensitization detected against both class I and class II antigens in our patient group. When some samples were reevaluated with the single-antigen bead method, desensitization values were shown to be considerably reduced compared with values from multiple antigen methods.

CONCLUSIONS

The single-antigen-coated bead method can be useful in determining the risk of donor-specific antibodies in highly sensitized patients.

Low-MFI (median fluorescence intensity) pre-transplant DSA (donor specific antibodies) leading to anamnestic antibody mediated rejection in live-related donor kidney transplantation

"In solid organ transplantation, the compatibility between recipient and donor relies on testing prior to transplantation as a major determinant for the successful transplant outcomes. This compatibility testing depends on the detection of donor-specific antibodies (DSAs) present in the recipient. Indeed, sensitized transplant candidates are at higher risk of allograft rejection and graft loss compared to non-sensitized individuals. Most of the laboratories in India have adopted test algorithms for the appropriate risk stratification of transplants, namely: 1) donor cell-based flow-cytometric cross-match (FCXM) assay with patient's serum to detect DSAs; 2) HLA-coated beads to detect anti-HLA antibodies; and 3) complement-dependent cytotoxicity crossmatch (CDCXM) with donor cells to detect cytotoxic antibodies. In the risk stratification strategy, laboratories generally accept a DSA median fluorescence index (MFI) of 1000 MFI or lower MFI (low-MFI) as a negative value and clear the patient for the transplant. We present two cases of live-related donor kidney transplants (LDKTs) with low-MFI pre-transplant DSA values who experienced an early acute antibody-mediated rejection (ABMR) as a result of an anamnestic antibody response by DSA against HLA class II antibodies. These results were confirmed by retesting of both pre-transplant and post-transplant archived sera from patients and freshly obtained donor cells. Our examples indicate a possible ABMR in patients with low MFI pre-transplant DSA. Reclassification of low vs. high-risk may be appropriate for sensitized patients with low-MFI DSA."

Successful desensitization of high level donor-specific anti-HLA antibody in patients with hematological diseases receiving haploidentical allografts

Donor-specific anti-human leukocyte antigen (HLA) antibody (DSA) is associated with a higher incidence of graft failure and mortality in HLA-mismatched allograft settings. However, the optimal protocol of desensitization for patients with positive DSA remains uncertain. We investigated the effectiveness of a desensitization protocol, including rituximab, high-dose intravenous immunoglobulin (IVIG), and a single session of plasma exchange (PE), for haploidentical allograft recipients with a high mean fluorescence intensity (MFI) level of DSA (≥ 5,000). Eleven patients with hematological disease who had positive DSA (median, 11,676, range 5387-20,435) were desensitized by the protocol. All of the patients achieved hematopoietic recovery. The median times for neutrophil and platelet engraftment were 13 (range, 11-26) days and 19 (range, 11-90) days, respectively. Grade II-IV acute graft-versus-host disease (GVHD) was seen in one patient and was controlled completely. Chronic cutaneous GVHD was seen in eight patients. Nine patients are alive with good performance so far. One patient suffered extramedullary relapse, and one patient died of transplantation-associated thrombotic microangiopathy. The 1-year probability of overall survival was 81.8%. These results suggest that successful desensitization could be obtained by a combination of rituximab, high-dose IVIG, and PE for haploidentical allograft recipients with high MFI levels of DSA.

Can PIRCHE-II Matching Outmatch Traditional HLA Matching?

We analyzed in a cohort of 68,606 first deceased donor kidney transplantations reported to the Collaborative Transplant Study whether an epitope-based matching of donor-recipient pairs using the Predicted Indirectly ReCognizable HLA Epitopes algorithm (PIRCHE-II) is superior to currently applied HLA antigen matching. PIRCHE-II scores were calculated based on split antigen HLA-A, -B, -DRB1 typing and adjusted to the 0–6 range of HLA mismatches. PIRCHE-II scores correlated strongly with the number of HLA mismatches (Spearman ρ = 0.65, P < 0.001). In multivariable analyses both parameters were found to be significant predictors of 5-year death-censored graft loss with high prognostic power [hazard ratio (HR) per adjusted PIRCHE-II score = 1.102, per HLA mismatch = 1.095; z-value PIRCHE-II: 9.8, HLA: 11.2; P < 0.001 for both]. When PIRCHE-II scores and HLA mismatches were analyzed simultaneously, their predictive power decreased but remained significant (PIRCHE-II: P = 0.002; HLA: P < 0.001). Influence of PIRCHE-II was especially strong in presensitized and influence of HLA mismatches in non-sensitized recipients. If the level of HLA-incompatibility was low (0–3 mismatches), PIRCHE-II scores showed a low impact on graft survival (HR = 1.031) and PIRCHE-II matching did not have additional significant benefit (P = 0.10). However, if the level of HLA-incompatibility was high (4–6 mismatches), PIRCHE-II improved the positive impact of matching compared to applying the traditional HLA matching alone (HR = 1.097, P = 0.005). Our results suggest that the PIRCHE-II score is useful and can be included into kidney allocation algorithms in addition to HLA matching; however, at the resolution level of HLA typing that is currently used for allocation it cannot fully replace traditional HLA matching.

Pre-transplant HLA Antibodies and Delayed Graft Function in the Current Era of Kidney Transplantation

Delayed graft function (DGF) occurs in a significant proportion of deceased donor kidney transplant recipients and was associated with graft injury and inferior clinical outcome. The aim of the present multi-center study was to identify the immunological and non-immunological predictors of DGF and to determine its influence on outcome in the presence and absence of human leukocyte antigen (HLA) antibodies. 1,724 patients who received a deceased donor kidney transplant during 2008–2017 and on whom a pre-transplant serum sample was available were studied. Graft survival during the first 3 post-transplant years was analyzed by multivariable Cox regression. Pre-transplant predictors of DGF and influence of DGF and pre-transplant HLA antibodies on biopsy-proven rejections in the first 3 post-transplant months were determined by multivariable logistic regression. Donor age ≥50 years, simultaneous pre-transplant presence of HLA class I and II antibodies, diabetes mellitus as cause of end-stage renal disease, cold ischemia time ≥18 h, and time on dialysis >5 years were associated with increased risk of DGF, while the risk was reduced if gender of donor or recipient was female or the reason for death of donor was trauma. DGF alone doubled the risk for graft loss, more due to impaired death-censored graft than patient survival. In DGF patients, the risk of death-censored graft loss increased further if HLA antibodies (hazard ratio HR=4.75, P < 0.001) or donor-specific HLA antibodies (DSA, HR=7.39, P < 0.001) were present pre-transplant. In the presence of HLA antibodies or DSA, the incidence of biopsy-proven rejections, including antibody-mediated rejections, increased significantly in patients with as well as without DGF. Recipients without DGF and without biopsy-proven rejections during the first 3 months had the highest fraction of patients with good kidney function at year 1, whereas patients with both DGF and rejection showed the lowest rate of good kidney function, especially when organs from ≥65-year-old donors were used. In this new era of transplantation, besides non-immunological factors, also the pre-transplant presence of HLA class I and II antibodies increase the risk of DGF. Measures to prevent the strong negative impact of DGF on outcome are necessary, especially during organ allocation for presensitized patients.

Limited impact of pre-existing donor specific HLA-antibodies (DSA) on long term allograft survival after first adult liver transplantation

The relevance of pre-existing HLA-antibodies (HLA-Ab) in liver transplantation (LTx) is controversial. While livers are allocated without HLA match or preoperative crossmatch testing, several studies point to an impact of donor specific antibodies (DSA) for acute rejection, bile duct complications or even graft loss. To investigate the role of DSA in long term liver allograft survival we analysed 177 pre transplant sera of first LTx patients with Luminex single antigen technology defining a MFI of >1500 as positive. The analyses were done retrospectively, and the DSA results had no impact on graft acceptance or patients' therapy. Three year follow up was available for all patients. 77% of our patients had any HLA-Ab pre transplantation, 55 patients were transplanted with DSA by chance. Acute rejections or ischemic type bile duct lesions (ITBL) were not higher in the DSA group, but ITBL was associated with a higher donor age. There was no difference in long term graft function or survival in patients without HLA-Ab, with non DSA or with DSA (p = 0.712). We suggest that determination of pre-existing DSA in first LTx recipients is not appropriate and we conclude that pre-existing DSA in first LTx patients are not a contraindication for liver transplantation.

Flow Cytometry Panel-Reactive Antibody Screening of Anti-HLA Antibodies in the Waiting List Significantly Reduces the Occurrence of Acute Rejection After Kidney Transplantation

INTRODUCTION

The presence of preformed HLA-reactive antibodies in recipient serum before transplantation has long been recognized as a prominent risk factor for a generally worse graft outcome. Screening and identification of HLA antibodies can be used to stratify patients into high- and low-risk categories.

MATERIALS AND METHODS

We determined patients' anti-HLA antibodies using flow cytometry panel-reactive antibody (flowPRA) screening, specifying more than 5% after positive screening. According to the results of the screening test, patients were allocated to the induction immunosuppressive protocol according to the actual immunologic risk.

RESULTS

In the group of 78 patients, screening with flowPRA of anti-HLA antibodies was done twice a year. Patients were divided into 2 groups of immunologic risk (low or medium), and we chose the induction immunosuppressive protocol according to the risk. Stratification of the risk was correct, because the only predictor for development of acute rejection in the monitored period of 12 months was delayed graft function (odds ratio 33.2501; 95% confidence interval 10.0095-110.4508; P < .0001). The occurrence of acute rejection upon implementing the screening was reduced in our transplant center from 44% to 19% (P < .0001). No difference was recorded in the 12-month survival of grafts and patients according to the applied induction immunosuppressive protocol.

CONCLUSION

We confirmed significantly reduced occurrence of acute rejection in the follow-up period of 12 months by using individualized induction according to flowPRA screening of anti-HLA antibodies. FlowPRA screening represents a suitable alternative for screening and specification of anti-HLA antibodies in case the Luminex methodology is unavailable.

Survival Benefit of Transplantation with a Deceased Diabetic Donor Kidney Compared with Remaining on the Waitlist

BACKGROUND AND OBJECTIVES

Use of diabetic donor kidneys has been a necessary response to the donor organ shortage. Recipients of diabetic donor kidneys have higher mortality risk compared with recipients of nondiabetic donor kidneys. However, the survival benefit of transplantation with diabetic donor kidneys over remaining on the waitlist has not been previously evaluated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed an observational cohort study of 437,619 kidney transplant candidates from the Organ Procurement and Transplantation Network database, including 8101 recipients of diabetic donor kidneys and 126,560 recipients of nondiabetic donor kidneys. We used time-varying Cox proportional hazards modeling to assess the mortality risk of accepting a diabetic donor kidney compared with remaining on the waitlist or receiving a nondiabetic donor kidney.

RESULTS

Among transplant recipients, median follow-up was 8.9 years and mortality rate was 35 deaths per 1000 person-years. Recipients of diabetic donor kidneys had 9% lower mortality compared with remaining on the waitlist or transplantation with a nondiabetic donor kidney (adjusted hazard ratio, 0.91; 95% confidence interval, 0.84 to 0.98). Although recipients of nondiabetic donor kidneys with a Kidney Donor Profile Index score >85% had lower mortality risk (adjusted hazard ratio, 0.86; 95% confidence interval, 0.81 to 0.91), recipients of diabetic donor kidneys with an index score >85% did not show any difference (adjusted hazard ratio, 1.09; 95% confidence interval, 0.97 to 1.22). Patients aged <40 years attained no survival benefit from transplantation with diabetic donor kidneys; diabetic patients at centers with long waitlist times attained the greatest survival benefit.

CONCLUSIONS

Diabetic donor kidneys appear associated with higher mortality risk compared with nondiabetic donor kidneys, but offer greater survival benefit compared with remaining on the waitlist for many candidates. Patients with high risk of mortality on the waitlist at centers with long wait times appear to benefit most from transplantation with diabetic donor kidneys.

Clinical Relevance of HLA Antibodies in Kidney Transplantation: Recent Data from the Heidelberg Transplant Center and the Collaborative Transplant Study

Herein, we summarize our recent findings from the international Collaborative Transplant Study (CTS) and Heidelberg Transplant Center regarding the role of HLA antibodies in kidney transplantation and their application into the clinical routine. Based on the antibody findings from the CTS serum study, an algorithm was developed in 2006 for the transplantation of high-risk sensitized patients at the Heidelberg Transplant Center which includes seven different pre- and posttransplant measures. Using this algorithm, the number of transplantations could be increased in high-risk presensitized patients and the previously existing impact of antibodies on graft survival could greatly be diminished but not totally eliminated. More recent findings led to the hypothesis that T cell help from a preactivated immune system supports the harmful effects of pretransplant donor-specific HLA antibodies that otherwise disappear in many cases after transplantation without any consequence.

Alloreactive T Cells to Identify Risk HLA Alleles for Retransplantation After Acute Accelerated Steroid-Resistant Rejection

The risk of rejection by cellular alloreactivity to the transplant donor is not routinely assessed. Here we analyzed alloreactive T cells in kidney transplant recipients and report how their detection may have helped to prevent rejection of a second kidney graft in a patient with a history of acute accelerated steroid-resistant nonhumoral rejection. Alloreactive CD4 and CD8 T cells were quantified using a flow-cytometric mixed lymphocyte reaction assay based on interferon-γ induction. A group of 16 nonrejecting transplant recipients did not show any alloreactive T-cell immunity to their respective donors, whereas alloreactivity to third-party controls was detectable. In the patient with rejection, HLA-specific antibodies were not detectable before and shortly after rejection, but after transplantation the patient showed exceptionally high frequencies of alloreactive T cells against 2 of 11 HLA-typed controls (0.604% and 0.791% alloreactive CD4 T cells and 0.792% and 0.978% alloreactive CD8 T cells) who shared HLA alleles (HLA-A*24, -B*44, -C*02, -DQB1*5) with the kidney donor. These HLA alleles were subsequently excluded for allocation of a second graft. No alloreactive T cells were observed toward the second kidney donor, and this transplantation was performed successfully. Thus, shared HLA alleles between the donor and third-party controls may suggest that alloreactive T cells had contributed to rejection of the first graft. The rejecting patient highlights that determination of cellular alloreactivity before transplantation may be applied to identify unacceptable mismatches and to reduce the risk for acute cellular rejection episodes.

Donor-specific antibodies require preactivated immune system to harm renal transplant

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Pretransplant DSA have a deleterious impact on graft survival only in the presence of high pretransplant serum levels of sCD30.

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The majority of patients with pretransplant DSA might be transplanted safely without special pretreatment measures.

Kidney transplantation in the presence of donor-specific HLA antibodies (DSA) is associated with a high failure rate due to antibody-mediated rejection. Many centers avoid transplantations if DSA are present. Others perform such transplantations after removal of DSA by apheresis under potent immunosuppression.

We provide strong evidence that DSA positive recipients reject their grafts at a high rate only if the immune activation marker sCD30 is also high, suggesting that T-cell help from an activated immune system is necessary for pretransplant DSA to exert a deleterious effect on the graft.

High-risk patients with DSA and sCD30 may benefit from special treatment measures. The presence of DSA alone may not be deleterious.

Background

It is an unresolved issue why some kidney transplant recipients with pretransplant donor-specific HLA antibodies (DSA) show a high transplant failure rate, whereas in other patients DSA do not harm the graft. We investigated whether help from preactivated T-cells might be necessary for DSA to exert a deleterious effect.

Methods

The impact of pretransplant DSA and immune activation marker soluble CD30 (sCD30) on 3-year graft survival was analyzed in 385 presensitized kidney transplant recipients.

Findings

A deleterious influence of pretransplant DSA on graft survival was evident only in patients who were positive for the immune activation marker sCD30. In the absence of sCD30 positivity, 3-year graft survival was virtually identical in patients with or without DSA (83.1 ± 3.9% and 84.3 ± 2.8%, P = 0.81). A strikingly lower 3-year graft survival rate of 62.1 ± 6.4% was observed in patients who were both sCD30 and DSA positive (HR 2.92, P < 0.001). Even in the presence of strong DSA with ≥ 5000 MFI, the 3-year graft survival rate was high if the recipients were sCD30 negative.

Interpretation

Pretransplant DSA have a significantly deleterious impact on graft survival only in the presence of high pretransplant levels of the activation marker sCD30.

Analysis of the Humoral Immune Response to Human Leukocyte Antigens in Turkish Renal Transplant Candidates and Relationship Between Autoimmune Disorders

BACKGROUND

Pre-transplant sensitization to human leukocyte antigens (HLA) is a risk factor for graft failure. The purpose of the current single-center study was to evaluate humoral immune response to HLA antigens and the possible relationship between anti-HLA antibody titer and autoimmune disorders in renal transplant candidates.

METHODS

A total of 435 renal transplant candidates were analyzed; 50 sensitized patients were enrolled in this study. The HLA typing was performed by use of enzyme-linked immunoassay combined with Luminex technology. The patients were questioned for clinical evidence of hypothyroidism and systemic lupus erythematosus (SLE) and investigated for anti-nuclear antibody (ANA), anti-double-stranded DNA (anti-dsDNA), anti-thyroglobulin (anti-TG), anti-thyroid peroxidase (anti-TPO) antibodies, and thyroid function tests.

RESULTS

Among 50 patients with positive panel reactive antibody, 24 (48%) were positive for class I and negative for class II, 12 (24%) were negative for class I and positive for class II, and 14 (28%) were positive for both classes I and II. The specificities of anti-HLA antibodies-A23, A68, A69, B27, B49, DR6, and DR8-were the most frequent. ANA and anti-dsDNA antibodies were not correlated with either clinical symptoms of SLE or anti-HLA antibody titer of renal transplant candidates. Similarly, anti-TG and anti-TPO antibodies were not correlated with clinical hypothyroidism or anti-HLA antibody titer.

CONCLUSIONS

Our data have demonstrated the profile of anti-HLA antibodies in patients who were on the renal transplant waiting list in Turkey. The most frequent specificities of anti-HLA antibodies were A23, A68, A69, B27, B49, DR6, and DR8. There was no association between anti-HLA antibody titer and clinical and laboratory evidence of SLE and hypothyroidism.

Human adipose tissue-derived mesenchymal stem cells abrogate plasmablast formation and induce regulatory B cells independently of T helper cells

Mesenchymal or stromal stem cells (MSC) interact with cells of the immune system in multiple ways. Modulation of the immune system by MSC is believed to be a therapeutic option for autoimmune disease and transplant rejection. In recent years, B cells have moved into the focus of the attention as targets for the treatment of immune disorders. Current B-cell targeting treatment is based on the indiscriminate depletion of B cells. The aim of this study was to examine whether human adipose tissue-derived MSC (ASC) interact with B cells to affect their proliferation, differentiation, and immune function. ASC supported the survival of quiescent B cells predominantly via contact-dependent mechanisms. Coculture of B cells with activated T helper cells led to proliferation and differentiation of B cells into CD19(+) CD27(high) CD38(high) antibody-producing plasmablasts. ASC inhibited the proliferation of B cells and this effect was dependent on the presence of T cells. In contrast, ASC directly targeted B-cell differentiation, independently of T cells. In the presence of ASC, plasmablast formation was reduced and IL-10-producing CD19(+) CD24(high) CD38(high) B cells, known as regulatory B cells, were induced. These results demonstrate that ASC affect B cell biology in vitro, suggesting that they can be a tool for the modulation of the B-cell response in immune disease.

Chronic Renal Transplant Rejection and Possible Anti-Proliferative Drug Targets

The global prevalence of renal transplants is increasing with time, and renal transplantation is the only definite treatment for end-stage renal disease. We have limited the acute and late acute rejection of kidney allografts, but the long-term survival of renal tissues still remains a difficult and unanswered question as most of the renal transplants undergo failure within a decade of their transplantation. Among various histopathological changes that signify chronic allograft nephropathy (CAN), tubular atrophy, fibrous thickening of the arteries, fibrosis of the kidney interstitium, and glomerulosclerosis are the most important. Moreover, these structural changes are followed by a decline in the kidney function as well. The underlying mechanism that triggers the long-term rejection of renal transplants involves both humoral and cell-mediated immunity. T cells, with their related cytokines, cause tissue damage. In addition, CD 20+ B cells and their antibodies play an important role in the long-term graft rejection. Other risk factors that predispose a recipient to long-term graft rejection include HLA-mismatching, acute episodes of graft rejection, mismatch in donor-recipient age, and smoking. The purpose of this review article is the analyze current literature and find different anti-proliferative agents that can suppress the immune system and can thus contribute to the long-term survival of renal transplants. The findings of this review paper can be helpful in understanding the long-term survival of renal transplants and various ways to improve it.

National outcomes of kidney transplantation from deceased diabetic donors

Use of deceased diabetic donor kidneys has increased over recent decades. However, scarce patient and allograft survival data are available taking into account recipient diabetes status. Here we performed a retrospective cohort study using data from the United Network of Organ Sharing in patients transplanted from 1994 to 2014. Multivariable Cox regression assessed recipient outcomes of 9074 diabetic vs. 152,555 non-diabetic donor kidneys. Recipients of diabetic donor kidneys had elevated rates of all-cause allograft failure (hazard ratio 1.21, 95% confidence interval 1.16-1.26) and death (1.19, 1.13-1.24) compared to recipients of kidneys from non-diabetic donors. Younger recipients of diabetic donor kidneys had worse allograft survival than older recipients of non-diabetic donor kidneys. There was significant interaction between donor and recipient diabetes status. To minimize the effect of unmeasured confounders, we used paired analyses of recipients of mate-kidneys from the same donor, with one diabetic recipient and the other non-diabetic. Among discordant recipient pairs of diabetic donor kidneys, diabetic recipients had significantly higher risk of allograft failure (1.27, 1.05-1.53) and death (1.53, 1.22-1.93) than non-diabetic recipients. After stratifying by Kidney Donor Profile Index risk category, diabetic recipients of diabetic donor kidneys continued to have worse allograft survival compared to all other patients. Thus, risks are associated with the use of diabetic donor kidneys. Understanding these risks will enable clinicians to better educate potential recipients.Kidney International advance online publication, 21 October 2015; doi:10.1038/ki.2015.325.

Peak panel reactive antibody, cancer, graft, and patient outcomes in kidney transplant recipients

BACKGROUND

High levels of pretransplant panel reactive antibodies (PRA) are known to be associated with detrimental effects on graft outcomes, but the association between pretransplant PRA levels and long-term patient outcomes is unclear.

METHODS

Using the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA), we assessed the risk of rejection, graft failure, mortality and cancer in kidney transplant recipients with varying peak PRA levels.

RESULTS

In 7,118 kidney transplant recipients between 1997 and 2009, there were a total of 3,171 (44.6%), 3,306 (46.4%), 323 (4.5%), and 318 (4.5%) recipients with peak PRA levels of 0%, 1% to 50%, 51% to 80%, and greater than 80%, respectively. Compared to recipients with 0% peak PRA level, recipients with peak PRA levels greater than 80% were at increased risk of acute rejection (odds ratio, 1.81, 95% confidence interval [95% CI], 1.30-2.35; P < 0.001), death censored graft failure (hazard ratio [HR], 2.06; 95% CI, 1.46-2.91; P < 0.001), all-cause mortality (HR, 1.56; 95% CI, 1.15-2.11; P < 0.001) and cancer (HR, 1.94; 95% CI, 1.26-2.97; P = 0.002) in the adjusted models independent of human leukocyte antigen mismatches and initial immunosuppression.

CONCLUSION

Highly sensitized kidney transplant recipients with peak PRA greater than 80% had a greater risk of rejection, graft failure, cancer and death independent of age and time on dialysis. Strategies to reduce transplant waiting time and avoidance of sensitization in all potential transplant candidates are imperative to improve the overall graft and patient survival.

Long-term outcome on kidney retransplantation: a review of 100 cases from a single center

Renal transplantation has become an effective form of treatment for end-stage renal failure. Unfortunately, as a consequence of immunological and nonimmunological pathogenic mechanisms, chronic allograft nephropathy is responsible for the loss of a large proportion of kidney grafts after several years and return to dialysis. We have reported herein our 24 years of experience with second kidney transplantations. Of 1,302 kidney transplantations between January 1983 and June 2007 performed in our transplantation center, 100 were second transplantations. Kidney retransplantation was performed in 74 men and 26 women of overall mean age of 35.4 +/- 12.6 years. Cadaveric donor grafts were transplanted in 92 patients, whereas the remaining 8 were living-related donor kidneys. At 1, 5, and 10 years after kidney transplantation, patient survival rates were 100%, 96%, and 92%, respectively, whereas graft survival rates were 85%, 72%, and 53%, respectively. Immunosuppressive therapy included induction therapy with polyclonal anti-lymphocyte antibodies (ALG/ATG) or (starting from 1999) monoclonal anti CD 25 antibody. Our results demonstrated good outcomes for kidney retransplantations with allocation based on anti- HLA antibody identification together with induction immunosuppression.

Pretransplant IgG reactivity to apoptotic cells correlates with late kidney allograft loss

Preexisting serum antibodies have long been associated with graft loss in transplant recipients. While most studies have focused on HLA-specific antibodies, the contribution of non-HLA-reactive antibodies has been largely overlooked. We have recently characterized mAbs secreted by B cell clones derived from kidney allograft recipients with rejection that bind to apoptotic cells. Here, we assessed the presence of such antibodies in pretransplant serum from 300 kidney transplant recipients and examined their contribution to the graft outcomes. Kaplan-Meier survival analysis revealed that patients with high pretransplant IgG reactivity to apoptotic cells had a significantly increased rate of late graft loss. The effect was only apparent after approximately 1 year posttransplant. Moreover, the association between pretransplant IgG reactivity to apoptotic cells and graft loss was still significant after excluding patients with high reactivity to HLA. This reactivity was almost exclusively mediated by IgG1 and IgG3 with complement fixing and activating properties. Overall, our findings support the view that IgG reactive to apoptotic cells contribute to presensitization. Taking these antibodies into consideration alongside anti-HLA antibodies during candidate evaluation would likely improve the transplant risk assessment.

Evaluation of the humoral immune response to human leukocyte antigens in Brazilian renal transplant candidates

Pre-transplant sensitization to human leukocyte antigens (HLA) is a risk factor for graft failure. Studies of the immunological profile related to anti-HLA antibodies in Brazilian renal transplant candidates are few. In this study, we evaluated the humoral immune response to HLA antigens in 269 renal transplant candidates, in Paraná State, Brazil. The HLA typing was performed by the polymerase chain reaction sequence-specific oligonucleotide method (PCR-SSO) combined with Luminex technology, using an SSO-LABType commercial kit (One Lambda, Inc., Canoga Park, CA, USA). The percentages of panel-reactive antibodies (PRA) and the specificity of anti-HLA antibodies were determined using the LS1PRA and LS2PRA commercial kits (One Lambda, Inc.). The PRA-positive group consisted of 182 (67.7%) patients, and the PRA-negative group of 87 (32.3%) patients. The two groups differed significantly only with respect to gender. Females were the most sensitized. Among the 182 patients with PRA- positive, 62 (34.1%) were positive for class I and negative for class II, 39 (21.4%) were negative for class I and positive for class II, and 81 (44.5%) were positive for both classes I and II. The HLA-A*02, A*24, A*01, B*44, B*35, B*15, DRB1*11, DRB1*04 and DRB1*03 allele groups were the most frequent. The specificities of anti-HLA antibodies were more frequent: A34, B57, Cw15, Cw16, DR51, DQ8 and DP14. This study documented the profile of anti-HLA antibodies in patients with chronic renal failure who were on waiting lists for an organ in Paraná, and found high sensitization to HLA antigens in the samples.

Desensitization for solid organ and hematopoietic stem cell transplantation

Desensitization protocols are being used worldwide to enable kidney transplantation across immunologic barriers, i.e. antibody to donor HLA or ABO antigens, which were once thought to be absolute contraindications to transplantation. Desensitization protocols are also being applied to permit transplantation of HLA mismatched hematopoietic stem cells to patients with antibody to donor HLA, to enhance the opportunity for transplantation of non-renal organs, and to treat antibody-mediated rejection. Although desensitization for organ transplantation carries an increased risk of antibody-mediated rejection, ultimately these transplants extend and enhance the quality of life for solid organ recipients, and desensitization that permits transplantation of hematopoietic stem cells is life saving for patients with limited donor options. Complex patient factors and variability in treatment protocols have made it difficult to identify, precisely, the mechanisms underlying the downregulation of donor-specific antibodies. The mechanisms underlying desensitization may differ among the various protocols in use, although there are likely to be some common features. However, it is likely that desensitization achieves a sort of immune detente by first reducing the immunologic barrier and then by creating an environment in which an autoregulatory process restricts the immune response to the allograft.

Superiority of AbCross enzyme-linked immunosorbent assay cross-match over the B-cell complement-dependent lymphocytotoxicity cross-match

BACKGROUND

The AbCross enzyme-linked immunosorbent assay (ELISA) cross-match is a recently introduced solid phase cross-match technique with several technical advantages over the currently available Antibody Monitoring System ELISA cross-match.

METHODS

In the present study, we investigated the potential superiority of AbCross over the traditional complement-dependent lymphocytotoxicity (CDC) B-cell cross-match (BXM). Pretransplant sera of 271 kidney transplant recipients who were transplanted at our center between 1998 and 2010 were tested in ELISA screening for the presence of human leukocyte antigen (HLA) antibodies and in AbCross and CDC for antibody reactivity against solubilized donor HLA class I and II antigens and donor B cells, respectively.

RESULTS

Patients positive for HLA class I or II antibodies on ELISA screening had a significantly poorer graft outcome 2 years after transplantation than recipients who were negative for HLA antibodies (21% vs 6% graft loss; P = .002). Corresponding with this finding, 37 recipients positive for HLA antibodies in AbCross against donor HLA class I or II antigens had a 2-year post-transplant graft loss rate of 19%, which is significantly higher than the 8% rate in 186 recipients who were negative for both antibody classes in AbCross (P = .043). The 2-year graft loss rate in 34 AbCross positive but BXM negative patients was 21%, compared with 7% in 172 AbCross and BXM negative patients (P = .012) and 9% in 11 AbCross negative but BXM positive patients (P = .39).

CONCLUSIONS

Our data indicate that the AbCross ELISA cross-match is superior to the CDC BXM, most likely because it detects antibodies against donor HLA antigens at a higher sensitivity.

Significance of pre-transplant anti-HLA antibodies detected on an ELISA mixed antigen tray platform

This study aims at examining the clinical impact, of antibodies detected on an ELISA mixed antigen tray format (LATM, One Lambda) in the absence of complement dependent cytotoxicity (CDC) positivity. All patients who underwent renal transplantation in 2007 and 2008 had their final pre-transplant sera retrospectively analyzed by the LATM assay. These patients were then followed-up with clinical, biochemical, and histopathological end points defined by elevation of serum creatinine and/or histopathological criteria. Among 164 patients who were studied, 149 received grafts from live related donors and 15, from deceased donors. 31 (19%) of the transplanted patients demonstrated pre-transplant anti-HLA IgG antibodies on the assay. Totally, 15 were positive for class I antibodies, 4 for class II antibodies, and 12 for both class I and class II antibodies. 44 patients (36%) experienced rejection. 8 out of 31 (26%) ELISA positive patients and 36 out of 133 (27%) ELISA negative patients experienced rejection. Among 15 patients who received deceased donor transplants, 4 were positive for ELISA, and 11 were negative. All 4 (100%) of the ELISA positive patients experienced rejection as compared to 3 out of 11 (27%) ELISA negative patients (P = 0.01). The ELISA LATM assay did not show any predictive value for rejection in our overall patient population; however, results in the specific setting of deceased donor transplants merit further exploration.

Technical aspects of HLA antibody testing

PURPOSE OF REVIEW

Since the landmark studies of Patel and Terasaki, pretransplant identification of donor-directed HLA alloantibodies (DSAs) has been a critical prelude to renal allograft transplantation. Pretransplant, DSAs may be an acceptable risk or an unconditional contraindication to transplantation depending on the particular donor : recipient combination. Posttransplant, DSAs are associated with episodes of acute rejection, chronic rejection, and graft loss. Thus, monitoring for such antibodies is an important aspect of patient care.

RECENT FINDINGS

The development of solid-phase antibody detection assays significantly enhanced our ability to identify HLA antibodies, taking virtual crossmatching from concept to reality. At the root of these detection assays are two questions that have been asked for almost 50 years: are donor-directed HLA antibodies present and, if so, are they clinically relevant? While the technology related to solid-phase antibody detection has seemingly allowed the first question to be answered with exquisite sensitivity and specificity, can the same be said for question 2?

SUMMARY

Solid-phase antibody detection assays have clear benefits over historical approaches to antibody identification, but are not flawless. In fact, the limitations of these assays are frequently ignored. Herein, the strengths and weaknesses of solid-phase antibody detection are highlighted.

Early post-transplant immune monitoring can predict long-term kidney graft survival: soluble CD30 levels, anti-HLA antibodies and IgA-anti-Fab autoantibodies

This study aimed to investigate the predictive power of anti-HLA antibodies, sCD30 levels and IgA-anti-Fab autoantibody before and early after transplantation in relation to long-term kidney allograft survival. Pre- and post-transplant sera samples of 59 living-unrelated donor kidney recipients were tested for above risk factors by enzyme-linked immunoabsorbent assay. 15 out of 59 cases experienced rejection episodes (failure group). Pre- and post-transplant high sCD30 levels were significantly associated with graft failure (P=0.02 and P=0.004) and decreased 4 year graft survival (P = 0.009 and P = 0.001). Higher frequency of post-transplant HLA class-II antibody in the absence of class-I antibody was observed in failure group (P=0.007). Patients with post-transplant HLA class-I and class-II antibodies either alone or in combination showed significant lower 4 year graft survival. Recipients with high sCD30 levels in the presence of HLA class-I or class-II antibodies within 2 weeks post-transplant had poor graft survival (P = 0.004 and P = 0.002, respectively). High levels of post-transplant IgA-anti-Fab antibody was more frequent in functioning-graft patients (P = 0.00001), correlated with decreased serum creatinine levels (P = 0.01) and associated with improved graft survival (P = 0.008). Our findings indicate the deleterious effect of early post-transplant HLA antibodies and increased sCD30 levels dependently and protective effect of IgA-anti-Fab antibodies on long-term renal graft outcomes.

Influence of test technique on sensitization status of patients on the kidney transplant waiting list

The exquisitely sensitive single antigen bead (SAB) technique was shown to detect human leukocyte antigen (HLA) antibodies in sera of healthy male blood donors. Such false reactions can have an impact on critical decisions, especially with respect to the determination of unacceptable HLA-antigen mismatches in patients awaiting a kidney transplant. We tested pretransplant sera of 534 patients on the kidney waiting list using complement-dependent cytotoxicity (CDC), enzyme-linked immunosorbent assay (ELISA) and SAB in parallel. Evidence of HLA antibodies was obtained in 5% of patients using CDC, 14% using ELISA, and 81% using SAB. Among patients without history of an immunizing event, 77% showed evidence of HLA antibodies in SAB. In contrast 98% of these patients were negative in ELISA and CDC. In patients without an immunizing event, SAB-detected antibodies reacted not always weakly but with mean fluorescence intensity (MFI) values as high as 14 440. High-MFI-value antibodies were found in some of these patients with HLA specificities that are rather common in general population, consideration of which would lead to unjustified exclusion of potential kidney donors. False SAB reactions can be unveiled by testing with additional antibody assays. Denial of donor kidneys to recipients based on HLA-antibody specificities detected exclusively in the SAB assay is not advisable.

Algorithms for the determination of unacceptable HLA antigen mismatches in kidney transplant recipients

One of the major tasks of human leukocyte antigen (HLA) laboratories is the pretransplant determination of unacceptable HLA antigen mismatches (UAM) in organ transplant recipients. HLA antigen specificities are determined against which the patient has circulating alloantibodies that are expected to harm the transplanted organ. Using the information on UAM, negative crossmatch (XM) prediction or 'virtual XM' is possible when a potential donor's complete HLA typing is available. Before the introduction of solid-phase antibody detection assays, UAM were determined using the complement-dependent cytotoxicity methodology. After the introduction of the single antigen bead technique, however, various UAM determination algorithms have emerged. In this report, six different laboratories worldwide present how they determine UAM in their collective of kidney transplant recipients in the pretransplant phase and proceed thereafter to transplantation.

Four-year allograft survival in a highly sensitized combined liver-kidney transplant patient despite unsuccessful anti-HLA antibody reduction with rituximab, splenectomy, and bortezomib

Although donor-specific lymphocytotoxic antibodies are regarded as a contraindication for kidney transplantation (KTx), the data available for liver or combined liver or kidney transplantation (cLKTx) are scarce. Here, we report a case of a highly sensitized young man receiving his sixth liver and second kidney graft. Multiple anti-HLA antibodies were present at the time of transplantation. As a result of suspected antibody-mediated graft damage, the patient was treated with rituximab, plasmapheresis, intravenous immunoglobulins, splenectomy, and bortezomib to decrease the antibody production. So far, patient and allograft survival has reached 4 years despite failure to achieve a permanent reduction of anti-HLA antibodies, and particularly nondonor directed antibodies.

Role and Value of Luminex(®)-Detected HLA Antibodies before and after Kidney Transplantation

SUMMARY

The complement-dependent lymphocytotoxicity (CDC) method has been the classical technique to detect human leukocyte antigen (HLA) antibodies in sera of patients who are listed for kidney transplantation. Because of the drawbacks of CDC, such as low sensitivity and low resolution in characterizing antibody specificities, the more specific ELISA technology was introduced in the 1990s which utilizes solubilized HLA molecules instead of lymphocytes. During the last 10 years, the introduction of the Luminex-based single antigen bead (L-SAB) technology, which uses recombinant single HLA molecules, allows detection and characterization of HLA antibodies at greater sensitivity than CDC and ELISA. A drawback associated with this technique is that the interpretation of results is demanding and requires comprehensive experience in HLA antibody diagnostics. Herein we discuss the current role and value of L-SAB technology in the clinical management of sensitized kidney transplant recipients.

Immune reactivity of renal transplant recipients receiving interleukin-2 receptor antagonists during the early posttransplant period

PURPOSE

There is a need for methods that would enable monitoring of the effects of immunosuppression on the recipient's immune system to avoid rejection, immunodeficiency-related complications and non-immune toxicities of the drugs used in therapy.

METHODS

This prospective trial included thirty patients who underwent renal transplantation in our center. All patients received an interleukin-2 receptor (IL-2R) antagonist in combination with mycophenolate, corticosteroid and calcineurin inhibitor. During the first 6 weeks after transplantation, the anti-CD3-stimulated proliferative response of peripheral blood T lymphocytes (PBTL) was studied by cell cycle analysis. The proportion of PBTL in different phases of the cell cycle and expression of IL-2R were determined by flow cytometry.

RESULTS

As an effect of quadruple immunosuppressive therapy including IL-2R antagonists, cell cycle analysis showed an incremental decrease in the proliferative response of PBTL during the first 6 weeks after renal transplantation. A sudden drop in the proportion of IL-2R-positive cells was observed immediately after the first dose of the IL-2R antagonist and a significant antiproliferative effect on PBTL after the second dose. In vitro, IL-2R antagonists showed a dose-dependent inhibition of the anti-CD3-stimulated proliferation of PBTL of healthy blood donors.

CONCLUSIONS

Cell cycle analysis of the immune reactivity of renal allograft recipients may represent a valuable tool for the immunological posttransplant follow-up and optimization of the immunosuppressive therapy.

Peritubular capillaritis in early renal allograft dysfunction is an indicator of acute rejection

BACKGROUND

Kidneys showing acute rejection (AR) processes often are accompanied by various levels of peritubular capillaritis (Ptc), especially cases of acute humoral rejection (AHR). However, it is not known whether the presence of Ptc alone is sufficient evidence of allograft rejection. This study was performed to determine the diagnostic value of Ptc as a marker for AR among cases of early renal allograft dysfunction.

METHODS

Fifty-three AR showed C4d deposition in the peritubular capillaries (PTCs; C4d+AR group), 50 AR were without C4d deposition (C4d-AR group), 30 had Ptc alone (Ptc group), 28 had acute tubular necrosis (ATN group), and 78 were surveillance biopsies (control group).

RESULTS

Analyzing the immunophenotype of infiltrating T lymphocytes and serum antibodies, discovered that 85.9% of control biopsies presented with a regulatory phenotype. Among the Ptc cohort, 93.3% of biopsies showed the cytotoxic phenotype with no significant different between C4d+AR and C4d-AR (96.2% vs 92.0%). We also observed the prevalence of panel-reactive antibody (PRA) and major-histocompatibility-complex class I chain-related gene A (MICA) antibodies to be increased among Ptc (30.0% and 43.3%, respectively), albeit not significantly different from C4d+AR (49.1% and 39.6%, respectively). The prevalences were low in other groups.

CONCLUSIONS

These results implied that Ptc in biopsy specimens from patients with early renal allograft dysfunction was an indicator of AR, especially AHR.

Study of the allogeneic response induced by endothelial cells expressing HLA class II after lentiviral transduction

Rejection is still the major cause of allograft loss following organ transplantation and a more complete comprehension of the alloimmune response is required in order to develop new therapeutic approaches. Allogenicity is primarily generated by the expression of major histocompatibility complex (MHC) molecules in the donor organ. Graft microvascular endothelial cells express both HLA class I and class II molecules. They are the first target of the allogeneic response because of their vascular localization and are also able to present antigen to recipient T cells. The endothelium can therefore be considered as both a stimulator of and a target for alloimmune responses and both aspects require further study. We have established a model of constitutive expression of HLA-DR by human microvascular endothelial cells following transduction with a lentiviral vector. This model was employed in a study demonstrating that endothelial cells can induce allogeneic expansion of regulatory and pro-inflammatory CD4(+) T lymphocyte subsets. Because microvascular endothelial cells rapidly lose their expression of HLA-DR ex vivo, this experimental system of lentiviral-mediated expression of HLA-DR allows the study of alloantigen presentation without requiring addition of inflammatory cytokines and thus provides a model for the study of the intra-graft allogeneic CD4(+) T cell response at the single-cell level.

Prevention of antibody-mediated kidney transplant rejection

There is increasing evidence that antibody-mediated rejection is the major cause of late kidney graft failure. Prevention of antibody-mediated allograft damage has therefore become an important issue in kidney transplantation. Such prevention starts already before transplantation with the avoidance of sensitizing events. When a patient is already sensitized, precise characterization of alloantibodies and exact HLA typing of the donor at the time of transplantation are mandatory. To ensure timely and successful transplantation of highly sensitized patients, desensitization, and inclusion in special programs such as the Eurotransplant Acceptable Mismatch Program should be considered. After transplantation, close monitoring of kidney function, testing for the de novo development or changing characteristics of alloantibodies, and attention to non-adherence to immunosuppression is obligatory. In the current overview, we discuss the currently available measures for the prevention of antibody-mediated kidney graft rejection.

Allosensitization rate of male patients awaiting first kidney grafts after leuko-depleted blood transfusion

BACKGROUND

Blood transfusions are generally avoided for potential renal transplant recipients due to risk of human leukocyte antigen (HLA) allosensitization. Despite the near universal use of erythropoiesis-stimulating agents, there are still occasions when patients require blood transfusions for reasons such as resistance to erythropoiesis-stimulating agents or cardiovascular instability. The risk of allosensitization in renal patients is believed to be lower with leuko-depleted blood. We sought to quantify the risk of blood transfusion per se in male renal patients on the transplant waiting list for their first kidney graft, using sensitive solid phase antibody detection.

METHOD

Cross-sectional survey looking at the prevalence of HLA antibody detected using single antigen Luminex beads in male patients awaiting first renal transplantation.

RESULTS

One hundred sixteen male patients awaiting their first kidney transplant were identified on our waiting list. Seven of the 42 patients (16.7%) who received at least one unit of leuko-depleted blood developed HLA antibody (HLAab). Of the remaining 74 patients without a history of transfusion, 3 (4.1%) were found to have HLAab. All the antibodies identified were directed against class I antigens. A history of blood transfusion gave a relative risk of 4.1 of developing HLAab (P=0.02).

CONCLUSION

Male patients awaiting their first organ transplant had a fourfold increased risk of developing HLA antibody if they had been previously transfused when compared with those who did not have a history of a transfusion. Transfusion even in the postleukodepletion era continues to pose a significant risk of sensitization.