Donor-specific HLA antibodies and graft function in children after renal transplantation

Incidence, risk factors, management strategies, and outcomes of antibody-mediated rejection in pediatric kidney transplant recipients-a multicenter analysis of the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN)

BACKGROUND

This study by the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) was designed to determine the incidence, risk factors, current management strategies, and outcomes of antibody-mediated rejection (ABMR) in pediatric kidney transplant recipients (pKTR).

METHODS

We performed an international, multicenter, longitudinal cohort study of data reported to the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) registry. Three hundred thirty-seven pKTR from 21 European centers were analyzed. Clinical outcomes, including kidney dysfunction, rejection, HLA donor-specific antibodies, BK polyomavirus-associated (BKPyV) nephropathy, and allograft loss, were assessed through 5 years post-transplant.

RESULTS

The cumulative incidence of de novo donor-specific class I HLA antibodies (HLA-DSA) post-transplant was 4.5% in year 1, 8.3% in year 3, and 13% in year 5; the corresponding data for de novo class II HLA-DSA were 10%, 22.5%, and 30.6%, respectively. For 5 years post-transplant, the cumulative incidence of acute ABMR was 10% and that of chronic active ABMR was 5.9%. HLA-DR mismatch and de novo HLA-DSA, especially double positivity for class I and class II HLA-DSA, were significant risk factors for ABMR, whereas cytomegalovirus (CMV) IgG negative recipient and CMV IgG negative donor were associated with a lower risk. BKPyV nephropathy was associated with the highest risk of graft dysfunction, followed by ABMR, T-cell mediated rejection, and older donor age.

CONCLUSIONS

This study provides an estimate of the incidence of de novo HLA-DSA and ABMR in pKTR and highlights the importance of BKPyV nephropathy as a strong risk factor for allograft dysfunction.

Donor specific antibody surveillance among pediatric kidney transplant programs: A report from the improving renal outcome collaborative

BACKGROUND

Kidney transplantation (KT) is the preferred treatment for children with end-stage kidney disease. Recent advances in immunosuppression and advances in donor specific antibody (DSA) testing have resulted in prolonged allograft survival; however, standardized approaches for surveillance DSA monitoring and management of de novo (dn) DSA are widely variable among pediatric KT programs.

METHODS

Pediatric transplant nephrologists in the multi-center Improving Renal Outcomes Collaborative (IROC) participated in a voluntary, web-based survey between 2019 and 2020. Centers provided information pertaining to frequency and timing of routine DSA surveillance and theoretical management of dnDSA development in the setting of stable graft function.

RESULTS

29/30 IROC centers responded to the survey. Among the participating centers, screening for DSA occurs, on average, every 3 months for the first 12 months post-transplant. Antibody mean fluorescent intensity and trend most frequently directed changes in patient management. Increased creatinine above baseline was reported by all centers as an indication for DSA assessment outside of routine surveillance testing. 24/29 centers would continue to monitor DSA and/or intensify immunosuppression after detection of antibodies in the setting of stable graft function. In addition to enhanced monitoring, 10/29 centers reported performing an allograft biopsy upon detection of dnDSA, even in the setting of stable graft function.

CONCLUSIONS

This descriptive report is the largest reported survey of pediatric transplant nephrologist practice patterns on this topic and provides a reference for monitoring dnDSA in the pediatric kidney transplant population.

Impact of de novo donor-specific HLA antibodies on pediatric kidney transplant prognosis in patients with acute declined or stable allograft function

BACKGROUND

This retrospective multicenter long-term cohort study investigates de novo donor-specific HLA antibodies (dnDSA) impact on allograft survival in pediatric kidney transplantation (KTx), depending on allograft function at dnDSA detection.

METHODS

Seventy patients with dnDSA screening in the context of acute allograft dysfunction (AAD) (>50% serum creatinine increase) or routine follow-up were included during a 20-year period. Number of dnDSA specificities and HLA total mean fluorescence intensity (MFI-sum) were collected.

RESULTS

Median follow-up time was 8.6 years. Among the 22 dnDSA+ patients, 8 patients presented AAD. Compared with dnDSA- patients, allograft survival was shorter only in dnDSA+/AAD+ patients, regardless of dnDSA detection during the 5-year post-transplant period (9 patients) or later (13 patients) (log rank p < .001 and p < .001, respectively). One dnDSA+/AAD-, 7 dnDSA+/AAD+, and 5 dnDSA- patients lost their allograft. Allograft survival was shorter in dnDSA+/AAD+ patients compared with the 16 dnDSA-/AAD+ patients (log rank p < .001) but did not differ between dnDSA+/AAD- and dnDSA-/AAD- patients (log rank p = .157). dnDSA+/AAD+ and dnDSA-/AAD+ patients presented higher risk of allograft failure compared with the other patient groups after adjustment for recipient age at KTx, donor type, and incidence of delayed graft function (HR 11.322, 95% CI 3.094-41.429, p < .001). Concurrent MFI-sum >10 000 and multiple dnDSA specificities were more significantly associated with AAD, compared with each factor separately (p < .001).

CONCLUSIONS

In pediatric KTx, AAD shortens allograft survival in dnDSA+ patients, regardless of dnDSA time detection, and is commonly observed when high MFI-sum concurs with multiple dnDSA specificities. dnDSA without AAD incidence does not determinately affect allograft survival.

Outcomes of paediatric kidney transplant recipients using the updated 2013/2017 Banff histopathological classification for antibody-mediated rejection

BACKGROUND

After the major changes with regard to acute and chronic ABMR in the Banff classification initiated in 2013, there has been an improvement in diagnosing antibody-mediated rejection (ABMR) in adult studies but no data have been published in the paediatric population.

METHODS

We assessed 56 paediatric kidney transplant biopsies due to kidney dysfunction in patients with donor-specific antibodies (DSA) in a retrospective single-centre study between January 2006 and March 2012. The results were compared with 2003/2007 Banff classification noting the subsequent 2017 and 2019 modifications do not change the 2013 Banff classification with regard to acute antibody-mediated rejection (apart from the addition of gene transcripts/classifiers that do not affect our analysis).

RESULTS

Following the 2013 Banff classification, there were seven cases (12.5%) diagnosed with ABMR that would have been misclassified when applying the 2003/2007 classification. Evaluating the histological features of all ABMR-related cases, we report the importance of v- (intimal arteritis) and t- (tubulitis) lesions: absence of v- and t- lesions in the biopsy is related to significantly higher kidney allograft survival (OR 7.3, 95%CI 1.1-48.8, p = 0.03 and OR 5.3, 95%CI 1.2-25.5, p = 0.04 respectively). Moreover, absence of t- lesions was associated with significantly fewer rejection episodes the year after the initial biopsy (OR 5.1, 95%CI 1.4-19.8, p = 0.01).

CONCLUSIONS

Our study supports that the updated 2013 Banff classification shows superior clinicopathological correlation in identifying ABMR in paediatric kidney transplant recipients. Our results can be extrapolated to the recently updated 2019 Banff classification.

Pretransplant Donor-Specific Anti-HLA Antibodies and the Risk for Rejection-Related Graft Failure of Kidney Allografts

Background

The presence of donor-specific antibodies (DSAs) against HLA before kidney transplantation has been variably associated with decreased long-term graft survival. Data on the relation of pretransplant DSA with rejection and cause of graft failure in recipients of donor kidneys are scarce.

Methods

Patients transplanted between 1995 and 2005 were included and followed until 2016. Donor-specific antibodies before transplantation were determined retrospectively. For cause, renal transplant biopsies were reviewed.

Results

Pretransplant DSAs were found in 160 cases on a total of 734 transplantations (21.8%). In 80.5% of graft failures, a diagnostic renal biopsy was performed. The presence of pretransplant DSA (DSApos) increased the risk of graft failure within the first 3 months after transplantation (5.2% vs. 9.4%) because of rejection with intragraft thrombosis (p < 0.01). One year after transplantation, DSApos recipients had an increased hazard for antibody-mediated rejection at 10 years (9% DSAneg vs. 15% DSApos, p < 0.01). One year after transplantation, DSApos recipients had an increased hazard for antibody-mediated rejection at 10 years (9% DSAneg vs. 15% DSApos, p < 0.01). One year after transplantation, DSApos recipients had an increased hazard for antibody-mediated rejection at 10 years (9% DSAneg vs. 15% DSApos.

Conclusions

Pretransplant DSAs are a risk factor for early graft loss and increase the incidence for humoral rejection and graft loss but do not affect the risk for T cell-mediated rejection.

Age-associated decrease in de novo donor-specific antibodies in renal transplant recipients reflects changing humoral immunity

Background

Older age at organ transplantation is associated with increased risk of infection and malignancy but reduced risk of cellular rejection. De novo donor-specific anti-HLA antibodies (dnDSA), are key biomarkers associated with reduced long-term allograft survival, yet there is a lack of data focusing on age-associated changes.

Methods

Development of dnDSA was restrospectively analyzed in all subjects who received a kidney transplant at the University Hospital Zurich between 01/2006 and 02/2015. Follow up continued until 03/2016. The incidence of dnDSA in different age categories was compared with special focus on the extremes of age: children < 10 years (n = 19) and adults ≥60 years of age (n = 110).

Results

Incidence of dnDSA gradually decreased with age, with older recipients having a significantly lower risk (HR 0.21, p = 0.0224) compared to pediatric recipients. Cumulative incidence of dnDSA at 2, 5 and 10 years was 6.2, 9.1 and 36% in the older recipients versus 5.3, 29.5 and 47.1% in pediatric recipients. Median time to development of dnDSA was similar (older 720 days, min 356, max 3646 days; children 1086 days, min 42, max 2474 days). Annual incidence was highest within the first two years after transplantation in the older recipients and peaked in years two to four in pediatric recipients. DnDSA were predominantly class II. More dnDSA were observed with cyclosporine as compared to tacrolimus.

Conclusion

Older kidney transplant recipients have a lower risk of developing dnDSA than pediatric recipients, pointing towards reduced humoral immune reactivity with increasing age. This observation raises the question of adjustment in immunosuppression.

Evaluation of the current post-transplantation Human Leukocyte Antigen antibody screening in pediatric renal transplant recipients

The necessity of post-transplant monitoring for donor-specific antibodies (DSAs) is unclear. This study evaluates the clinical relevance of post-transplantation donor-specific HLA antibodies in pediatric renal transplant recipients, aiming at better stratification of patients at risk of graft dysfunction and better recommendations for post-transplant monitoring. A cohort of 68 pediatric kidney recipients, involving 76 transplantations between 2004 and 2014, was studied retrospectively. All patients were screened for HLA antibodies at 1, 3, 6, and 12 months after transplantation and yearly thereafter. Samples testing positive were further analyzed to detect DSA. A biopsy was performed on clinical indication. We studied the baseline characteristics of the patients with biopsy, with DSA, and with rejection. We assessed the effect of post-transplant DSA on clinical outcome, including antibody-mediated acute rejection and GFR decrease. In our cohort, the prevalence of DSA was 19% (13/68 transplantations). Most patients with HLA antibodies after transplantation were DSA-positive (76%; 13/17). A clear association between DSA and subsequent rejection was found. At the end of the study period, a significantly lower GFR was found in patients with biopsy, DSA, or rejection. Based on our observations, we recommend routine post-transplantation screening for HLA and DSA. The presence of DSA justifies a renal biopsy even in the absence of clinical signs of rejection.

Results of early treatment for de novo donor-specific antibodies in pediatric kidney transplant recipients in a cross-sectional and longitudinal cohort

The development of dnDSA anti-HLA antibodies has been shown to be a significant risk factor for graft failure. In 2008, we instituted a routine protocol of standardized monitoring and treatment of dnDSA in pediatric kidney transplant recipients. Of 67 first-time pediatric kidney transplant recipients, 26 (38%) developed dnDSA after 1.36 (IQ 1-2.14) years. Coefficient of variance of tacrolimus, a surrogate marker of non-adherence, was found to be the single most important risk factor for dnDSA development. Overall, there was a significant reduction in dnDSA with treatment in 19 (76%) children. No difference in graft survival and estimated glomerular filtration rate was noted between dnDSA negative and those treated for dnDSA. There was an increased risk of hospitalization in those treated for dnDSA. This study suggests that early detection and treatment of dnDSA can help to prevent graft failure and preserve graft function in the short term. Future studies and longer follow-up are needed to fully elucidate the effect of early detection and treatment of dnDSA in pediatric kidney transplant recipients.

Donor-specific HLA antibodies and graft function in kidney-transplanted children - the Vienna cohort

In the pediatric population, little is known on de novo DSA development, its impact on graft function, and association with suboptimal IS. We assessed the prevalence of de novo DSA in the Vienna cohort of 40 renal transplanted children and adolescents and prospectively followed its association with clinical parameters, graft function, and proteinuria for one yr. At the cross-sectional analysis (median post-transplant time of five yr), 17% of the patients had developed de novo DSA. All HLA-Ab were anti-HLA class II antibodies and persisted in 85% of the cases until the follow-up screening performed within one yr. Basic clinical and laboratory parameters did not differ between DSA-negative and DSA-positive patients at the time of HLA-Ab screening. Suboptimal IS due to reduced medication or non-adherence could not be proven in DSA-positive patients. The changes in eGFR did not differ during the prospective study period, but there was a significantly higher proteinuria in the DSA-positive patients during the follow-up. Our data demonstrate an overall prevalence of 17% of de novo DSA in a pediatric renal transplant cohort. During 12 months of prospective follow-up time, we could demonstrate a significant impact of de novo DSA presence on proteinuria.

Renal transplantation in infants

Renal transplantation (RTx) has become an accepted mode of therapy in infants with severe renal failure. The major indications are structural abnormalities of the urinary tract, congenital nephrotic syndrome, polycystic diseases, and neonatal kidney injury. Assessment of these infants needs expertise and time as well as active treatment before RTx to ensure optimal growth and development, and to avoid complications that could lead to permanent neurological defects. RTx can be performed already in infants weighing around 5 kg, but most operations occur in infants with a weight of 10 kg or more. Perioperative management focuses on adequate perfusion of the allograft and avoidance of thrombotic and other surgical complications. Important long-term issues include rejections, infections, graft function, growth, bone health, metabolic problems, neurocognitive development, adherence to medication, pubertal maturation, and quality of life. The overall outcome of infant RTx has dramatically improved, with long-term patient and graft survivals of over 90 and 80 %, respectively.

Donor-specific antibodies after pediatric liver transplantation: a cross-sectional study of 50 patients

The role of donor-specific HLA antibodies (DSAs) after pediatric liver transplantation (LT) is inadequately established. We conducted a cross-sectional study on the prevalence of DSAs and their association with liver histology and biochemical variables after pediatric LT. Serum samples were drawn for HLA antibody analyses from 50 patients (76% of 66 eligible patients) operated on at age <18 years between 1987 and 2007 with a median of 10.0 (interquartile range 4.0-16.4) years after deceased donor LT. Mixed and single-antigen beads with Luminex were used for HLA antibody screening and detection. A mean fluorescence intensity (MFI) value of 1000 was used for positive cutoff. Twenty-six patients (52%; 95% confidence interval (CI) 39% to 65%) had DSAs. In 22 (85%) patients, DSAs were against class II HLA antigens with a mean (standard deviation) MFI of 13,481 (4727). The unadjusted prevalence ratio for portal inflammation in DSA-positive compared to DSA-negative patients (n = 47; 9/24 vs. 1/23) was 8.6 (95% CI 1.6 to 50.9). Laboratory values at the time of study were comparable between DSA-positive and DSA-negative patients. In conclusion, approximately half of patients studied had DSAs after pediatric LT. Portal inflammation was associated with DSA positivity although the wide confidence interval around the ratio estimate warrants cautious interpretation.

Minimum mycophenolic acid levels are associated with donor-specific antibody formation

Although de novo DSA are associated with inferior graft survival, there are no effective strategies to prevent their formation. Underexposure to MPA (prodrug: MMF) also contributes to rejection rates early after transplantation, but the effect of this phenomenon on the formation of DSA long-term post-transplantation is unknown. Data are expressed as mean (standard deviation). All available data from 32 renal transplant recipients (age at transplantation 7.5 [4.5] yr) on tacrolimus and MPA immunosuppression with an average follow-up of 9.4 (s.d. 4.6) yr were analyzed. DSA were measured using the Luminex assay (>500 MFI was considered DSA-positive). Tacrolimus and MPA levels were measured with the Abbot Tacro II and EMIT assay, respectively. Among 1964 MPA and 3462 tacrolimus trough levels, the average MPA trough level was 3.2 (1.5) mg/L and the average tacrolimus level was 6.7 (2.8) ng/mL. At last follow-up, only 5/32 patients had undetectable DSA, with 5/32 having no class I antibodies and 6/32 having no class II antibodies. DSA formation was associated with a lower minimum MPA trough level (0.27 [0.23] vs. 0.47 [0.18] mg) and cystatin C eGFR (48 [21] vs. 70 [23] mL/min/1.73 m(2)) for class I DSA formers. The average eGFR of patients without class I DSA was 70 (23) mL/min/1.73 m(2), whereas the average eGFR of patients with class I DSA was 48 (21) mL/min/1.73 m(2) (p = 0.0071). MPA trough levels <1.3 mg/L long-term post-transplantation are associated with the formation of DSA. The association between the formation of DSA and minimum MPA exposure may support a strategy for preventing the formation of DSA.

Donor-specific anti-HLA antibodies in pediatric renal transplant recipients with creeping creatinine: Prevalence, histological correlations, and impact on patient and graft survival

Donor-specific anti-HLA antibodies (DSA) causing CAMR are responsible for a high proportion of long-term graft failures after RTX. We studied the prevalence of DSA in RTX children biopsied for creeping Cr, its relationship with NA, and patient and graft survival according to histopathology. Between 2008 and 2013, 92 children were biopsied at a median of 38 months post-RTX. At biopsy, the prevalence of DSA was 49% and C4d 70%. NA rate was 45%, higher in adolescents (60%). Most frequent diagnoses were CAMR (72%) and interstitial fibrosis with tubular atrophy (IFTA) (28%). Forty-five of 66 patients with CAMR (68%) had detectable DSA. Twenty-one DSA-negative patients with CAMR had histological damage (IFTA + C4d positivity). C4d was detected in 64 of 66 biopsies with CAMR. Recipients with IFTA alone had neither C4d, nor detectable DSA, and were adherent. Graft survival at five yr was 89% in patients with CAMR, 79% in those with CAMR + TCMR Banff I, 33% in those with CAMR + TCMR Banff II, and 96% in those with IFTA. ABMR and complement activation were frequent in children biopsied for creeping Cr. Recipients with DSA were more likely to be non-adherent and have CAMR or CAMR + TCMR and worse graft survival.

The clinical spectrum of de novo donor-specific antibodies in pediatric renal transplant recipients

The development of donor-specific HLA antibodies (DSA) is associated with worse renal allograft survival in adult patients. This study assessed the natural history of de novo DSA, and its impact on renal function in pediatric renal transplant recipients (RTR). HLA antibodies were measured prospectively using single-antigen-bead assays at 1, 3, 6 and 12 months posttransplant followed by 12-monthly intervals and during episodes of allograft dysfunction. Of 215 patients with HLA antibody monitoring, 75 (35%) developed DSA at median of 0.25 years posttransplant with a high prevalence of Class II (70%) and HLA-DQ (45%) DSA. DSA resolved in 35 (47%) patients and was associated with earlier detection (median, inter-quartile range 0.14, 0.09-0.33 vs. 0.84, 0.15-2.37 years) and lower mean fluorescence intensity (MFI) (2658, 1573-3819 vs. 7820, 5166-11 990). Overall, DSA positive patients had more rapid GFR decline with a 50% reduction in GFR at mean 5.3 (CI: 4.7-5.8) years versus 6.1 (5.7-6.4) years in DSA negative patients (p = 0.02). GFR decreased by a magnitude of 1 mL/min/1.73 m(2) per log10 increase in Class II DSA MFI (p < 0.01). Using Cox regression, independent factors predicting poorer renal allograft outcome were older age at transplant (hazard ratio 1.1, CI: 1.0-1.2 per year), tubulitis (1.5, 1.3-1.8) and microvasculature injury (2.9, 1.4-5.7). In conclusion, pediatric RTR with de novo DSA and microvasculature injury were at risk of allograft failure.

Recent developments in kidney transplantation in children

PURPOSE OF REVIEW

Renal transplantation in childhood is a well established procedure with excellent short-term outcomes. However, waiting times for transplantation are still relatively long if living donation cannot be performed, and long-term outcomes after transplantation have not significantly improved during the last decade.

RECENT FINDINGS

This review describes alternative modalities to improve donation rates such as en bloc kidney transplantation from young donors, ABO-incompatible transplantation and kidney paired donation. This review also deals with long-term post-transplant morbidities, such as follows: first, medication side-effects (metabolic syndrome, cardiovascular disease) and with the benefits of steroid and calcineurin inhibitor drug minimization; second, the deleterious impact of viral infections and their management and third, chronic antibody-mediated rejection, its therapeutic and prevention possibilities.

SUMMARY

Donor shortage and long-term morbidities, after transplantation, are still relevant issues in paediatric renal transplantation medicine. Significant research and efforts have been made to advance the field and create novel approaches for improvement of transplantation rates and post-transplant graft or patient survival. These modalities are to be established in the routine setting.

Pediatric kidney recipients may benefit from monitoring for donor-specific antibodies

There are limited data regarding the presence of DSAs and their effect on graft function in pediatric renal transplantation. The role for serial DSA monitoring in routine clinical practice is unclear. All patients attending a regional transplant clinic were tested for DSAs, measured using Luminex single/mixed antigen beads. Any patient having a positive result subsequently underwent historic testing on samples previously obtained. DSA-positive patients underwent prospective monitoring of DSAs, and correlation with clinical events was studied. Nine of a total of 50 patients (18%) were DSA-positive, of whom six had graft dysfunction. The DSA-positive cohort had significantly increased episodes of AR (p = 0.01). There were two graft losses in the DSA-positive group and none in the DSA-negative group. Eight of the DSA-positive group had potentially reduced exposure to IS because of either adherence issues or clinical indications. DSAs were associated with increased risk of rejection. There appears to be a role for serial monitoring of DSAs in patients where there has been a reduced exposure to IS so that early intervention with optimized IS can be considered.

Long-term outcomes of children after solid organ transplantation

Solid organ transplantation has transformed the lives of many children and adults by providing treatment for patients with organ failure who would have otherwise succumbed to their disease. The first successful transplant in 1954 was a kidney transplant between identical twins, which circumvented the problem of rejection from MHC incompatibility. Further progress in solid organ transplantation was enabled by the discovery of immunosuppressive agents such as corticosteroids and azathioprine in the 1950s and ciclosporin in 1970. Today, solid organ transplantation is a conventional treatment with improved patient and allograft survival rates. However, the challenge that lies ahead is to extend allograft survival time while simultaneously reducing the side effects of immunosuppression. This is particularly important for children who have irreversible organ failure and may require multiple transplants. Pediatric transplant teams also need to improve patient quality of life at a time of physical, emotional and psychosocial development. This review will elaborate on the long-term outcomes of children after kidney, liver, heart, lung and intestinal transplantation. As mortality rates after transplantation have declined, there has emerged an increased focus on reducing longer-term morbidity with improved outcomes in optimizing cardiovascular risk, renal impairment, growth and quality of life. Data were obtained from a review of the literature and particularly from national registries and databases such as the North American Pediatric Renal Trials and Collaborative Studies for the kidney, SPLIT for liver, International Society for Heart and Lung Transplantation and UNOS for intestinal transplantation.

Neither pre-transplant rituximab nor splenectomy affects de novo HLA antibody production after renal transplantation

The long-term effect of rituximab and splenectomy on de novo HLA antibody production and chronic antibody-mediated rejection after renal transplantation is uncertain. In order to gain insight on this, we studied 92 ABO-incompatible and 228 ABO-identical/compatible consecutive renal transplant patients and determined their de novo HLA antibody production and graft outcome. Patients with pretransplant donor-specific antibodies had been excluded. ABO-incompatible transplants included 30 recipients treated with rituximab, 51 by splenectomy, or 11 with neither, due to low anti-A or -B antibody titer. Graft survival in ABO-identical/compatible patients (97.7% at 5 years) was significantly higher than in ABO-incompatible (87.0% at 5 years), rituximab (96.7% at 3 years), or splenectomy (85.7% at 5 years) patients. Only four patients had clinical chronic antibody-mediated rejection (two each identical/compatible and incompatible). There was no significant difference in prevalence of de novo HLA antibody, including donor-specific and nondonor-specific antibodies among ABO-identical/compatible patients (13.9%), patients receiving rituximab (14.3%) or splenectomy (13.2%), or among those receiving cyclosporine, tacrolimus, mycophenolate mofetil, mizoribine, and everolimus. Renal function remained stable in most recipients with de novo HLA antibody. Thus, neither pretransplant splenectomy nor rituximab treatment has an inhibitory effect on de novo HLA antibody production during medium-term follow-up. Further study on long-term effects is needed.

Posttransplant de novo donor-specific hla antibodies identify pediatric kidney recipients at risk for late antibody-mediated rejection

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti-HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor-specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical-pathologic data. At 4.3-year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non-DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA-DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody-mediated rejection (AMR), and four C4d-negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1-year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab-negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.