Beyond Histology: Lowering Human Leukocyte Antigen Antibody to Improve Renal Allograft Survival in Acute Rejection

The Clinical Impact of Anti-HLA Donor Specific Antibody Detection Through First Year Screening on Stable Kidney Transplant Recipients

Anti-HLA Donor Specific Antibody (DSA) detection post kidney transplant has been associated with adverse outcomes, though the impact of early DSA screening on stable patients remain unclear. We analyzed impact of DSA detection through screening in 1st year stable patients (n = 736) on subsequent estimated glomerular filtration rate (eGFR), death censored graft survival (DCGS), and graft failure (graft loss including return to dialysis or re-transplant, patient death, or eGFR < 20 ml/min at last follow up). Patients were grouped using 1st year screening into DSA+ (Class I, II; n = 131) or DSA- (n = 605). DSA+ group were more DR mismatched (p = 0.02), more sensitized (cPRA ≥90%, p = 0.002), less Caucasian (p = 0.04), and had less pre-emptive (p = 0.04) and more deceased donor transplants (p = 0.03). DSA+ patients had similar eGFR (54.8 vs. 53.8 ml/min/1.73 m², p = 0.56), DCGS (91% vs. 94%, p = 0.30), and graft failure free survival (76% vs. 82%, p = 0.11). DSA timing and type did not impact survival. Among those with a protocol biopsy (n = 515), DSA detected on 1st year screening was a predictor for graft failure on multivariate analysis (1.91, 95% CI 1.03-3.55, p = 0.04). Overall, early DSA detection in stable patients was an independent risk factor for graft failure, though only among those who underwent a protocol biopsy.

Preformed Donor-specific Antibodies Against HLA Class II and Graft Outcomes in Deceased-donor Kidney Transplantation

Background

Many kidney transplant centers in the United States report both HLA class I and II antibodies detected by sensitive solid-phase assays (SPAs) to United Network for Organ Sharing as unacceptable antigens, significantly reducing the compatible donor organ pool and prolonging waiting time for highly sensitized patients. However, the clinical relevance of all detected donor-specific antibodies (DSAs) by SPA is not unequivocal, because fluorescence intensity does not always accurately reflect antibody pathogenicity. Our center does not exclude patients from transplantation based on DSA class II.

Methods

We performed a retrospective analysis in 179 deceased-donor kidney transplant recipients with solely DSA class II before transplant and patients without DSA and compared graft survival, rejection, and clinical outcomes. Patient survival was also compared with matched controls on the waiting list.

Results

Patients transplanted with DSA class II showed a clear survival benefit compared with matched patients who remained on dialysis or were waitlisted on dialysis/transplanted at 5 years (100%, 34%, and 73%, respectively). After a mean follow-up of 5.5 years, there was no significant difference in death-censored graft survival between transplanted patients without DSA and those with preformed DSA class II (adjusted HR 1.10; 95% confidence interval, 0.41-2.97), although the incidence of rejection was higher in recipients with DSA class II (adjusted HR 5.84; 95% confidence interval, 2.58-13.23; P < 0.001). Serum creatinine levels at 1, 3, and 5 years posttransplant did not differ between groups. No predictors of rejection were found, although patients who received basiliximab induction therapy had higher incidence of rejection (100%) compared with those who received antithymocyte globulin (52%).

Conclusions

We conclude that for highly sensitized patients, deceased-donor kidney transplantation with DSA class II yields a survival benefit over prolonged waiting time on dialysis. Instead of listing DSA class II as unacceptable antigens, an individual approach with further immunologic risk assessment is recommended.

Failure to remove de novo donor-specific HLA antibodies is influenced by antibody properties and identifies kidney recipients with late antibody-mediated rejection destined to graft loss - a retrospective study

Current research is focusing on identifying bioclinical parameters for risk stratification of renal allograft loss, largely due to antibody-mediated rejection (AMR). We retrospectively investigated graft outcome predictors in 24 unsensitized pediatric kidney recipients developing HLA de novo donor-specific antibodies (dnDSAs), and treated for late AMR with plasmapheresis + low-dose IVIG + Rituximab or high-dose IVIG + Rituximab. Renal function and DSA properties were assessed before and longitudinally post treatment. The estimated GFR (eGFR) decline after treatment was dependent on a negative % eGFR variation in the year preceding treatment (P = 0.021) but not on eGFR at treatment (P = 0.74). At a median follow-up of 36 months from AMR diagnosis, 10 patients lost their graft. Altered eGFR (P < 0.001) and presence of C3d-binding DSAs (P = 0.005) at treatment, and failure to remove DSAs (P = 0.01) were negatively associated with graft survival in the univariable analysis. Given the relevance of DSA removal for therapeutic success, we analyzed antibody properties dictating resistance to anti-humoral treatment. In the multivariable analysis, C3d-binding ability (P < 0.05), but not C1q-binding, and high mean fluorescence intensity (P < 0.05) were independent factors characterizing DSAs scarcely susceptible to removal. The poor prognosis of late AMR is related to deterioration of graft function prior to treatment and failure to remove C3d binding and/or high-MFI DSAs.

Complement-binding anti-HLA antibodies are independent predictors of response to treatment in kidney recipients with antibody-mediated rejection

A major hurdle to improving clinical care in the field of kidney transplantation is the lack of biomarkers of the response to antibody-mediated rejection (ABMR) treatment. To discover these we investigated the value of complement-binding donor-specific anti-HLA antibodies (DSAs) for evaluating the response to treatment. The study encompassed a prospective cohort of 139 kidney recipients with ABMR receiving the standard of care treatment, including plasma exchange, intravenous immunoglobulin and rituximab. Patients were systematically assessed at the time of diagnosis and three months after treatment initiation for clinical and allograft histological characteristics and anti-HLA DSAs, including their C1q-binding ability. After adjusting for clinical and histological parameters, post-treatment C1q-binding anti-HLA DSA was an independent and significant determinant of allograft loss (adjusted hazard ratio 2.57 (95% confidence interval 1.29-5.12). In 101 patients without post-treatment C1q-binding anti-HLA DSA there was a significantly improved glomerular filtration rate with significantly reduced glomerulitis, peritubular capillaritis, interstitial inflammation, tubulitis, C4d deposition, and endarteritis compared with 38 patients with posttreatment C1q-binding anti-HLA DSA. A conditional inference tree model identified five prognostic groups at the time of post-treatment evaluation based on glomerular filtration rate, presence of cg lesion and C1q-binding anti-HLA DSA (cross-validated accuracy: 0.77). Thus, circulating complement-binding anti-HLA DSAs are strong and independent predictors of allograft outcome after standard of care treatment in kidney recipients with ABMR.

Outcomes of Prolonged Treatment With Intravenous Immunoglobulin Infusions for Acute Antibody-mediated Rejection in Kidney Transplant Recipients

BACKGROUND

Treatment of antibody-mediated rejection (AMR) is one of the main problems after kidney transplantation (KTx). The results of intensive AMR treatment with plasmapheresis (PF) and repeated infusions of intravenous immunoglobulin (IVIg) are presented.

METHODS

Diagnosis of AMR was based on graft biopsy and the presence of donor-specific antibodies (DSAs). AMR therapy consisted of 5 PF and IVIg infusions given after the last PF. Subsequent IVIg doses were given every 4 weeks for 6 months. Graft biopsy and DSA assessment were repeated at the end of the treatment (ET).

RESULTS

Four women and 10 men were included in our study; mean time from KTx to AMR was 79 (range, 3-193) months. During the treatment, 4 patients had graft failure. Graft function at baseline was significantly worse (P = .02) in this group compared with patients who completed the therapy. At baseline, mean flourescence intensity (MFI) was 6574 (range, 852-15,917) in the whole group, 7088 (range, 1054-15,917) in patients who completed treatment, and 4828 (range, 852-11,797) in patients who restarted hemodialysis. At ET, DSA MFI decreased in 8 of 10 patients (80%) who completed the therapy. The MFI decrease was 3946 (range, 959-11,203). Control graft biopsies revealed decreased intensity of C4d deposits in peritubular capillaries in 7 patients (78%) and decreased peritubular capillaritis in 2 patients (22%).

CONCLUSION

Intensive, prolonged AMR therapy with PF and IVIg resulted in a decrease in DSA titer and intensity of C4d deposits, but was not associated with reduction of microcirculation inflammation. Treatment was ineffective in patients with baseline advanced graft insufficiency.

Dynamic Prognostic Score to Predict Kidney Allograft Survival in Patients with Antibody-Mediated Rejection

No tool is available for the early assessment of response to antibody-mediated rejection (ABMR) therapies in kidney allograft recipients. This study was designed to define a dynamic composite prognostic ABMR score to predict kidney allograft survival, integrating the disease characteristics at diagnosis and the response to treatment. Among 1978 kidney recipients who underwent transplant between 2008 and 2014, we included 278 patients diagnosed with active ABMR and receiving standard treatment, including plasma exchange, intravenous Ig, and rituximab. Patients were prospectively assessed at diagnosis and after treatment for clinical data, histologic characteristics (allograft biopsy specimen), and donor-specific anti-HLA antibodies (DSA). The dynamic ABMR prediction model included GFR (P<0.001) and presence of interstitial fibrosis/tubular atrophy (P=0.003) at diagnosis and changes in GFR (P<0.001), peritubular capillaritis Banff score (P=0.002), and DSA mean fluorescence intensity (P<0.001) after treatment. Overall, this model showed good calibration and discrimination (C-statistic=0.84). The ABMR prognostic score derived from the prediction model identified three risk strata with 6-year kidney allograft survival rates of 6.0% (high-risk group, n=40), 44.9% (intermediate-risk group, n=36), and 84.4% (low-risk group, n=202), and it provided greater net clinical benefit to patients than did considering them all to have the same level of risk of allograft loss. The performance of the ABMR prognostic score was validated in an independent cohort of 202 kidney recipients with ABMR (C-statistic=0.79). The ABMR prognostic score could be used to inform therapeutic decisions in clinical practice and for the design of clinical trials.

Histocompatibility and management of the highly sensitized kidney transplant candidate

PURPOSE OF REVIEW

Increasing national participation in kidney paired donation and implementation of new sharing policies via the current kidney allocation system have brought about greater opportunities for the most highly sensitized patients awaiting a kidney transplant. The purpose of this review is to discuss the application of histocompatibility data in the context of the clinical practice of kidney transplantation as pertains to the sensitized candidate.

RECENT FINDINGS

With desensitization techniques, transplantation across virtually any antibody barrier is technically feasible, but long-term outcomes after transplantation are improved when the immunologic match between donor and recipient is optimized. Solid-phase immunoassays have changed the landscape of histocompatibility testing. These sensitive and specific assays for identifying donor-specific antibody not only help determine feasibility of transplantation but have enabled outcomes studies aimed at understanding the spectrum of risk posed by different antibody profiles. This, in turn, has helped guide decision-making in donor selection, in particular for sensitized patients.

SUMMARY

Careful evaluation of donor-specific antibody profiles with individualized, patient-specific determination of unacceptable antigens is necessary to ensure that highly sensitized patients receive every opportunity for transplantation.

Prevalence and Clinical Impact of Donor-Specific Alloantibody Among Intestinal Transplant Recipients

BACKGROUND

Rejection remains the leading cause of allograft loss, and a major barrier to improving long-term outcomes after intestinal transplantation. Our aim is to define the prevalence and investigate the role of donor-specific antibody (DSA) on intestinal graft outcomes.

METHODS

The study includes 109 transplants performed in 95 recipients at a single center. Patients were screened for DSA pretransplant, monitored regularly posttransplant and when clinically indicated using the single-antigen bead Luminex assay. Standard induction immunosuppression was with interleukin-2 receptor antagonists, and antithymocyte globulin in high-risk recipients. Maintenance regimens were tacrolimus-based.

RESULTS

Pretransplant DSA was detected in 12 (11%) recipients with 50% continuing to have circulating antibodies posttransplant. An additional 24 (25%) patients developed de novo DSA, and of these, 71% had persistent antibodies. Recipients with preformed DSA demonstrated elevated risks of early graft failure, whereas those with de novo DSA experienced accelerated graft loss once DSA was detected, reaching a 28% failure rate within 2 years. HLA-DQ mismatch is a significant risk factor for de novo DSA emergence, whereas the persistence of antibodies is predicted by DSA strength and specificity. Although inclusion of the liver in the intestinal allograft imparts an immunological advantage against rejection-related graft loss, this protective effect was lost among recipients with persistent DSA.

CONCLUSIONS

The presence of DSA is associated with inferior graft outcomes among intestinal transplant recipients. An enhanced understanding of the mechanisms by which DSA causes allograft injury, and effective strategies targeting humoral immune reactivity are needed to improve long-term intestinal graft outcomes.

Luminex Solid-Phase Crossmatch for De Novo Donor-Specific Antibodies in Living-Donor Related Transplants

OBJECTIVES

There are no reports of de novo donor-specific antibody monitoring by a low-cost solid-phase crossmatch assay using donor lysate after renal transplant.

MATERIALS AND METHODS

We prospectively evaluated 121 complement-dependant cytotoxicity crossmatch-negative living-donor kidney transplant recipients for development of de novo donor-specific antibodies (class I and II HLA) by solid-phase crossmatch Luminex assay after transplant.

RESULTS

Of 121 recipients in our study group, 26 (21.5%) developed de novo donor-specific antibody within 3 months after transplant. Fifteen (58%) of these 26 recipients developed class II de novo donor-specific antibody, 8 patients (30%) developed class I, and 3 (12%) developed both class I and class II. Of the remaining 95 patients (79%) who did not develop de novo donor-specific antibody, 6 (33.3%) had antibody-mediated rejection with glomerulitis (2 with C4d-positive disease). Donor-specific antibody was detected by Luminex solid-phase crossmatch in 18 patients (5 with class I, 11 with class II, and 2 with both class I and II), all with no evidence of clinical rejection. Development of de novo donor-specific antibody detected by solid-phase crossmatch was associated with more acute rejection (31% in de novo donor-specific antibody-positive group versus 19% in the negative group). The positive group had more antibody-mediated rejection (75% of acute rejections), whereas only 33.3% of acute rejections in the negative group were antibody-mediated rejection. Of 12 patients with antibody-mediated rejection, 9 were C4d negative (75%) and were diagnosed by donor-specific antibody positivity detected by solid-phase cros?match testing and histologic findings. The use of donor lysate in solid-phase crossmatch assays is more economical than the single-antigen bead Luminex assay (per test cost of US $45.20 vs $403.20).

Treatment of Antibody-Mediated Renal Allograft Rejection: Improving Step by Step

Throughout the past years we stepwise modified our immunosuppressive treatment regimen for patients with antibody-mediated rejection (ABMR). Here, we describe three consecutive groups treated with different regimens. From 2005 until 2008, we treated all patients with biopsy-proven ABMR with rituximab (500 mg), low-dose (30 g) intravenous immunoglobulins (IVIG), and plasmapheresis (PPH, 6x) (group RLP, n = 12). Between 2009 and June 2010, patients received bortezomib (1.3 mg/m², 4x) together with low-dose IVIG and PPH (group BLP, n = 11). In July 2010, we increased the IVIG dose and treated all subsequent patients with bortezomib, high-dose IVIG (1.5 g/kg), and PPH (group BHP, n = 11). Graft survival at three years after treatment was 73% in group BHP as compared to 45% in group BLP and 25% in group RLP. At six months after treatment median serum creatinine was 2.1 mg/dL, 2.9 mg/dL, and 4.2 mg/dL in groups BHP, BLP, and RLP, respectively (p = 0.02). Following treatment, a significant decrease of donor-specific HLA antibody (DSA) mean fluorescence intensity from 8467 ± 6876 to 5221 ± 4711 (p = 0.01) was observed in group BHP, but not in the other groups. Our results indicate that graft survival, graft function, and DSA levels could be improved along with stepwise modifications to our treatment regimen, that is, the introduction of bortezomib and high-dose IVIG treatment.

Use of complement binding assays to assess the efficacy of antibody mediated rejection therapy and prediction of graft survival in kidney transplantation

BACKGROUND

The Luminex® single antigen bead assay (SAB) is the method of choice for monitoring the treatment for antibody-mediated rejection (AMR). A ⩾50% reduction of the dominant donor-specific antibody (IgG-DSA) mean fluorescence intensity (MFI) has been associated with improved kidney allograft survival, and C1q-fixing DSA activity is associated with poor outcomes in patients with AMR. We aimed to investigate if C1q-DSA can be used as a reliable predictor of response to therapy and allograft survival in patients with biopsy-proven AMR.

METHODS

We tested pre- and post-treatment sera of 30 kidney transplant patients receiving plasmapheresis and low-dose IVIG for biopsy-proven AMR. IgG-DSA and C1q-DSA MFI were measured and correlated with graft loss or survival. Patients were classified as nonresponders (NR) when treatment resulted in <50% reduction in MFI of IgG-DSA and/or C1q-DSA was detectable following therapy.

RESULTS

Differences in the percentage of patients deemed NR depended upon the end-point criterion (73% by reduction in IgG-DSA MFI vs. 50% by persistent C1q-DSA activity). None of the seven patients with <50% reduction of IgG-DSA but non-detectable C1q-DSA-fixing activity after therapy experienced graft loss, suggesting that C1q-DSA activity may better correlate with response. Reduction of C1q-DSA activity predicted graft survival better than IgG-DSA in the univariate Cox analysis (20.1% vs. 5.9% in NR; log-rank P-value=0.0147).

CONCLUSIONS

A rapid reduction of DSA concentration below the threshold required for complement activation is associated with better graft survival, and C1q-DSA is a better predictor of outcomes than IgG-DSA MFI reduction.

Donor-Specific Antibody Monitoring: Where Is the Beef?

This review paper discusses the impact of de novo donor-specific antibodies (DSA) to donor HLA antigens in kidney transplantation and summarizes the benefits and challenges that exist with DSA monitoring. Post-transplant DSA is associated with worse allograft outcomes and its detection may precede or coincide with clinical, biochemical, and histologic allograft dysfunction. There are no absolute features of DSA testing results that perfectly discriminate between states of disease and health. In a state of antibody-associated graft dysfunction, removal or reduction in DSA may only provide clinical benefit for some. Furthermore, various factors influence test results, and detection of HLA antibodies must be interpreted within the appropriate clinical and laboratory context. The utility of DSA monitoring is further affected by the limited effectiveness of treatment for antibody-mediated rejection. Although DSA monitoring is potentially beneficial in some circumstances, the optimal screening and treatment strategies are still to be defined.

Repeated cycles of high-dose intravenous immunoglobulin and plasmapheresis for treatment of late antibody-mediated rejection of renal transplants

BACKGROUND/PURPOSE

Intravenous immunoglobulin (IVIG) plays a central role in the treatment of antibody-mediated rejection (AMR) of renal allografts, but the treatment outcomes for late AMR (>6 months after transplantation) are poor.

METHODS

We performed a retrospective study to assess the response patterns of IVIG-based (2 g/kg) desensitization for late AMR. Patients who received desensitization after the pathological diagnosis of late AMR positive for complement component C4d were grouped as the Desensitized Group and compared to a historical Control Group with complement component C4d positivity in retrospective stainings.

RESULTS

The 10-year graft survival of the Desensitized Group (73.9%, n = 35) was significantly better than that of the historical Control Group (35.0%, n = 40) without desensitization. In the Desensitized Group, a subgroup of patients (D2 Subgroup, n = 11), who responded to desensitization initially but deteriorated later, was identified to benefit from repeated cycles of desensitization at 31.1 ± 20.9 months. Patients receiving only one cycle of desensitization were further grouped into D1-good (n = 10) and D1-poor (n = 14) based on their long-term renal function. The D2 Subgroup patients did not exhibit significant improvements in renal function compared to the D1-poor patients, until 30 months after IVIG-based desensitization, suggesting desensitization therapy has a working window of approximately 24 months.

CONCLUSION

Repeated cycles of IVIG-based desensitization help stabilize long-term renal function in patients with persistent AMR.

New insights in antibody-mediated rejection

PURPOSE OF REVIEW

In the present review, we aim to describe the state of knowledge concerning antibody-mediated rejection (ABMR) spectrum and diagnosis criteria before analyzing the present and future promising leads regarding ABMR prognosis markers and treatment.

RECENT FINDINGS

Recent studies regarding complement-binding donor-specific antibodies and the molecular approach highlighted the unmet need for stratification tools for prognosis and treatment inside ABMR disease.

SUMMARY

ABMR is the leading cause of kidney allograft failure. The recent expansion of its spectrum is related to the paradigm of a continuous process, leading insidiously to a chronic form of ABMR and to the progressive acknowledgement of new entities (such as vascular ABMR, subclinical ABMR, C4d-negative ABMR). Considering the global picture of ABMR, the Banff classification gradually refined the diagnosis criteria so that it now describes a clinically relevant and coherent entity. Nevertheless, if the diagnosis mainly relies on conventional assessment, such as histological findings and circulating donor-specific antibodies, these criteria face serious limitations in terms of stratification of patients at risk of graft loss inside ABMR disease. Recently, new promising tools have emerged in order to identify long-term outcomes at the time of the diagnosis of rejection. In this regard, donor-specific antibodies' complement-fixing ability and the molecular approach contributed significantly. Currently, however, no clinically relevant surrogate marker of treatment efficiency is currently available.

Utility of HLA Antibody Testing in Kidney Transplantation

HLA antigens are polymorphic proteins expressed on donor kidney allograft endothelium and are critical targets for recipient immune recognition. HLA antibodies are risk factors for acute and chronic rejection and allograft loss. Solid-phase immunoassays for HLA antibody detection represent a major advance in sensitivity and specificity over cell-based methods and are widely used in organ allocation and pretransplant risk assessment. Post-transplant, development of de novo donor-specific HLA antibodies and/or increase in donor-specific antibodies from pretransplant levels are associated with adverse outcomes. Although single antigen bead assays have allowed sensitive detection of recipient HLA antibodies and their specificities, a number of interpretive considerations must be appreciated to understand test results in clinical and research contexts. This review, which is especially relevant for clinicians caring for transplant patients, discusses the technical aspects of single antigen bead assays, emphasizes their quantitative limitations, and explores the utility of HLA antibody testing in identifying and managing important pre- and post-transplant clinical outcomes.

Acute and chronic antibody-mediated rejection in pediatric kidney transplantation

Acute antibody-mediated rejection is a diagnostic challenge in renal transplantation medicine. However, it is an important diagnosis to make, since chronic antibody-mediated rejection (CAMR) is the main cause of long-term graft loss. Antibody-mediated rejection is diagnosed by detecting donor-specific antibodies (DSAs) in the blood in combination with observing typical histomorphological signs in kidney biopsy, as described in the Banff classification. Therapy is based on the removal of DSAs by administering intravenous immunoglobulins (IVIGs), plasmapheresis, or immunoadsorption. Reoccurrence of antibodies is diminished by the use of rituximab, increased immunosuppression, and in some cases additional experimental substances. A combination of these techniques has been shown to be successful in the majority of cases of acute and chronic antibody-mediated rejection. Routine DSA monitoring is warranted for early detection of antibody-mediated rejection.

High dose intravenous immunoglobulin therapy for donor-specific antibodies in kidney transplant recipients with acute and chronic graft dysfunction

BACKGROUND

Postkidney transplant donor-specific antibodies (DSA) have been identified as important contributors to graft loss. Few therapeutic options exist and have been met with limited success. We report outcomes in patients with de novo DSA and graft damage treated with a protocol of high-dose intravenous immunoglobulin (IVIG).

METHODS

Retrospective analysis of 28 kidney transplant recipients with de novo DSA and graft damage in the form of either chronic graft dysfunction (group 1, n=20) or a recent previous acute antibody-mediated rejection (AMR) episode (group 2, n=8) prescribed a standard regimen of high-dose (5 g/kg) IVIG dosed over 6 months.

RESULTS

Mean fluorescence intensity (MFI) of 70 total DSA decreased by 12%at the end of treatment (T1, P=0.14) and by 18%at last follow up (T2, P=0.035) compared with treatment initiation (T0) MFI. The most robust effect was seen in class I DSA (37% decrease at T2 versus T0, P=0.05) and in DSA from patients in group 2 (52% decrease at T2 versus T0, P=0.008). Graft function stabilized in patients in group 2 but continued to decline in those in group 1.

CONCLUSION

High-dose IVIG resulted in modest DSA MFI reductions in patients with previous graft damage, with a larger effect occurring in class I DSA in patients with a previous acute AMR. There was no clinical treatment benefit in patients with ongoing chronic graft damage, whereas high-dose IVIG may reduce the risk of chronic graft dysfunction in those with an acute AMR event.

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.

Use of bortezomib as anti-humoral therapy in kidney transplantation

This study aimed to investigate the effect of bortezomib in the desensitization and treatment of acute antibody mediated rejection (AAMR) in kidney transplantation. Nine patients who received bortezomib therapy for desensitization (DSZ group, n = 3) or treatment of AAMR (AAMR group, n = 6) were included in this study. In the DSZ group, 2 patients required DSZ owing to positive cross match and 1 owing to ABO mismatch with high baseline anti-ABO antibody titer (1:1,024). Bortezomib was used at 1, 3, 8, and 11 days from the start of the treatment. In the AAMR group, 3 patients showed full recovery of allograft function after bortezomib use and decrease in donor specific anti-HLA antibody (HLA-DSA). However, 3 patients did not respond to bortezomib and experienced allograft failure. In the DSZ group, negative conversion of T-CDC (complement-dependent cytotoxicity) was achieved, and HLA-DSA was decreased to lower than a weak level (median fluorescence intensity [MFI] < 5,000) in 2 patients. In the case of ABO mismatch kidney transplantation, the anti-A/B antibody titer decreased to below the target (≤ 1:16) after bortezomib therapy. Therefore, bortezomib could be an alternative therapeutic option for desensitization and treatment of AAMR that is unresponsive to conventional therapies.

Antibody-mediated rejection in liver transplantation: current controversies and future directions

Interest in the role of donor-specific human leukocyte antibodies in liver transplantation has been rekindled recently. Emerging evidence suggests that these antibodies may cause injury to the liver allograft. Here we review the clinical literature, highlight controversial results, and propose a path forward for the definition and better understanding of antibody-mediated injury to the liver.

Trends and characteristics in early glomerular filtration rate decline after posttransplantation alloantibody appearance

BACKGROUND

Approximately 7% to 9% of patients with donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA) fail within 1 year post-DSA onset. However, little is known as to how this DSA-associated failure temporally progresses. This longitudinal study investigates DSA's temporal relationship to allograft dysfunction and identifies predictors of allograft function's progressive deterioration post-DSA.

METHODS

A cohort of 175 non-HLA identical patients receiving their first transplant between March 1999 and March 2006 were analyzed. Protocol testing for DSA via single antigen beads was done before transplantation and at 1, 3, 6, 9, and 12 months after transplantation then annually. Estimated glomerular filtration rate (eGFR) was analyzed before and after DSA onset.

RESULTS

Forty-two patients developed DSA and had adequate eGFR information for analysis. Before DSA onset, the 42 patients had stable eGFR. By 1 year post-DSA, the cohort's eGFR was significantly lower (P<0.001); however, 30 of 42 had stable function. Twelve patients had failure or early allograft dysfunction (eGFR decline >25% from DSA onset). Those who failed early (by 1 year post-DSA) had more antibody-mediated rejection than stable patients (P=0.03). Late failures (after 1 year post-DSA) were predictable with evidence of early allograft dysfunction (eGFR decline >25% by 1 year post-DSA; P<0.001). Early allograft dysfunction preceded late failure by nearly 1 year.

CONCLUSIONS

DSA is temporally related to allograft function deterioration. However, in many cases, late allograft failures are preceded by early allograft dysfunction. Therefore, monitoring for early allograft dysfunction provides treating physicians with a window of opportunity for treatment or continued monitoring.

Impact of alloantibody strength in crossmatch negative DSA positive kidney transplantation

OBJECTIVES

The clinical relevance of pre-transplant "low-level" donor specific anti-HLA antibodies (DSAs) in crossmatch negative kidney transplant recipients remains unclear. To determine what level of DSA associates with antibody mediated rejection (AMR) could be the way to measure the clinical relevance of pre-transplant "low-level" donor specific anti-HLA antibodies (DSAs) in crossmatch negative kidney transplant recipients.

DESIGN AND METHODS

A retrospective analysis of 221 patients from October 2008 to December 2009 was included in this study. Sera were obtained pre-transplant and two weeks post-transplant and tested for DSA using LABScreen single antigen beads.

RESULTS

Among the 221 patients, 11 experienced AMR within 200days after transplant (5%). Pre-transplant DSA was associated with AMR at multiple mean fluorescence intensity (MFI) cutoffs (500, 1000, 2000, 3000, 5000; p=0.003, 0.001, 0.007, 0.003, and 0.003, respectively). No correlation was seen between acute T-cell mediated rejection (CMR) and pre-transplant DSA at any of the same MFI cutoffs. There was an increased risk of AMR with higher levels of pre-transplant DSA. Finally, an increase in DSA MFI from pre- to two weeks post-transplant was indicative of a higher probability of AMR.

CONCLUSION

Overall, this data supports using the single antigen bead to detect "low-level" DSA both pre- and post- as having a positive and persistent DSA may be predictive of higher AMR rates and poorer graft survival.

Consensus guidelines on the testing and clinical management issues associated with HLA and non-HLA antibodies in transplantation

BACKGROUND

The introduction of solid-phase immunoassay (SPI) technology for the detection and characterization of human leukocyte antigen (HLA) antibodies in transplantation while providing greater sensitivity than was obtainable by complement-dependent lymphocytotoxicity (CDC) assays has resulted in a new paradigm with respect to the interpretation of donor-specific antibodies (DSA). Although the SPI assay performed on the Luminex instrument (hereafter referred to as the Luminex assay), in particular, has permitted the detection of antibodies not detectable by CDC, the clinical significance of these antibodies is incompletely understood. Nevertheless, the detection of these antibodies has led to changes in the clinical management of sensitized patients. In addition, SPI testing raises technical issues that require resolution and careful consideration when interpreting antibody results.

METHODS

With this background, The Transplantation Society convened a group of laboratory and clinical experts in the field of transplantation to prepare a consensus report and make recommendations on the use of this new technology based on both published evidence and expert opinion. Three working groups were formed to address (a) the technical issues with respect to the use of this technology, (b) the interpretation of pretransplantation antibody testing in the context of various clinical settings and organ transplant types (kidney, heart, lung, liver, pancreas, intestinal, and islet cells), and (c) the application of antibody testing in the posttransplantation setting. The three groups were established in November 2011 and convened for a "Consensus Conference on Antibodies in Transplantation" in Rome, Italy, in May 2012. The deliberations of the three groups meeting independently and then together are the bases for this report.

RESULTS

A comprehensive list of recommendations was prepared by each group. A summary of the key recommendations follows. Technical Group: (a) SPI must be used for the detection of pretransplantation HLA antibodies in solid organ transplant recipients and, in particular, the use of the single-antigen bead assay to detect antibodies to HLA loci, such as Cw, DQA, DPA, and DPB, which are not readily detected by other methods. (b) The use of SPI for antibody detection should be supplemented with cell-based assays to examine the correlations between the two types of assays and to establish the likelihood of a positive crossmatch (XM). (c) There must be an awareness of the technical factors that can influence the results and their clinical interpretation when using the Luminex bead technology, such as variation in antigen density and the presence of denatured antigen on the beads. Pretransplantation Group: (a) Risk categories should be established based on the antibody and the XM results obtained. (b) DSA detected by CDC and a positive XM should be avoided due to their strong association with antibody-mediated rejection and graft loss. (c) A renal transplantation can be performed in the absence of a prospective XM if single-antigen bead screening for antibodies to all class I and II HLA loci is negative. This decision, however, needs to be taken in agreement with local clinical programs and the relevant regulatory bodies. (d) The presence of DSA HLA antibodies should be avoided in heart and lung transplantation and considered a risk factor for liver, intestinal, and islet cell transplantation. Posttransplantation Group: (a) High-risk patients (i.e., desensitized or DSA positive/XM negative) should be monitored by measurement of DSA and protocol biopsies in the first 3 months after transplantation. (b) Intermediate-risk patients (history of DSA but currently negative) should be monitored for DSA within the first month. If DSA is present, a biopsy should be performed. (c) Low-risk patients (nonsensitized first transplantation) should be screened for DSA at least once 3 to 12 months after transplantation. If DSA is detected, a biopsy should be performed. In all three categories, the recommendations for subsequent treatment are based on the biopsy results.

CONCLUSIONS

A comprehensive list of recommendations is provided covering the technical and pretransplantation and posttransplantation monitoring of HLA antibodies in solid organ transplantation. The recommendations are intended to provide state-of-the-art guidance in the use and clinical application of recently developed methods for HLA antibody detection when used in conjunction with traditional methods.

Concurrent acute cellular rejection is an independent risk factor for renal allograft failure in patients with C4d-positive antibody-mediated rejection

BACKGROUND

Identification of risk factors for renal allograft failure after an episode of acute antibody-mediated rejection (AMR) may help the outcome of this difficult-to-treat complication.

METHODS

During December 2003 to February 2011, 833 kidney graft recipients underwent 1120 clinically indicated biopsies at our center. We reviewed the biopsy results and identified 87 biopsy specimens from 87 patients positive for the degradation product of complement component 4 (C4d) and acute AMR. We generated Kaplan-Meier survival curves and performed a multivariable analysis using the Cox proportional hazards regression model to identify risk factors for allograft failure after C4d+ acute AMR.

RESULTS

Among the 87 patients, 26 had a diagnosis of acute AMR according to the Banff '09 classification schema, 29 had acute AMR and chronic active AMR, 18 had acute AMR and acute T-cell mediated rejection (TCMR), and 14 had acute AMR, chronic active AMR, and acute TCMR. Kaplan-Meier survival estimates showed that concurrent acute TCMR (P=0.001, Mantel-Cox log-rank test), concurrent chronic active AMR (P=0.03), and time to biopsy (P=0.04) are associated with graft survival. The Cox proportional hazards regression analysis identified that concurrent acute TCMR (hazard ratio, 2.59 [95% confidence interval, 1.21-5.55]; P=0.01) and estimated glomerular filtration rate (hazard ratio, 0.65 [95% confidence interval, 0.48-0.88]; P=0.01) are independent risk factors for allograft loss. Concurrent chronic active AMR or time to biopsy was not associated with graft failure by the multivariable Cox analysis.

CONCLUSIONS

Our single-center study has elucidated that concurrent acute TCMR in kidney transplant recipients with C4d+ acute AMR is an independent risk factor for graft failure. Level of allograft function at the time of diagnosis was also an independent predictor of graft loss.

Using donor-specific antibodies to monitor the need for immunosuppression

BACKGROUND

Experience with tolerance protocols has shown that none is perfect and that each escape from tolerance must be identified early to prevent graft failure. In addition, some test is needed for patients who are weaned off immunosuppression (IS) to forewarn of weaning failure. The usual measures of function--such as serum creatinine levels--are not sensitive enough to detect rejection in a timely manner.

METHODS

A study was carried out on 72 patients who received living-donor kidney transplants with clonal deletion protocol (total lymphoid irradiation or bortezomib), and followed with reduced doses of maintenance IS. Every month or every 2 months, a test was performed for donor-specific antibodies (DSA) using Luminex mixed and/or single antigen beads.

RESULTS

After transplantation, DSA developed in 17% of the patients at 6 months, 41% at 1 year, and 57% at 2 years, with 95% confidence limits of 10%, 28%; 30%, 55%; and 44%, 71%, respectively. Fifty-three percent of patients weaned IS to less than 10 mg prednisone daily experienced DSA within 3 months. Furthermore, prednisone dose (per 2.5 mg) and years after transplantation were inversely associated with DSA production (risk ratio 0.92 [95% confidence limits: 0.85, 0.99], and 0.70 [0.49, 1.00]).

CONCLUSIONS

DSA monitoring is highly effective for detecting escape from tolerance and reemergence of the immune response in weaned patients. DSA appearance was inversely proportional to the level of maintenance drugs in the weaning process. Measurement of DSA on a monthly basis is adequate for detection of the change in immune reactivity.

The immune-modulator AS101 reduces anti-HLA antibodies in sera of sensitized patients: a structural approach

BACKGROUND

Significant efforts are dedicated to identification of agents that eliminate anti-HLA antibodies (Ab) from sera of transplant candidates. Antibody titer following in vitro incubation of sera with desensitizing agents has shown to reflect the probability that a patient would benefit from clinical de-sensitization protocols. AS101 is a non-toxic, synthetic, organic tellurium compound. The aim of this research was to assess the ability of AS101 to reduce anti-HLA Abs and to identify patients likely to benefit from this effect.

METHODS

Sera of sensitized patients awaiting transplant were incubated in the presence of AS101. Measured mean fluorescence intensity (MFI) represents reactivity of anti HLA Abs in the serum, as detected by the Luminex platform. The repertoire of HLA antigen epitopes was recognized using HLA Matchmaker software.

RESULTS

AS101 Incubation caused a significant Ab titer decrease in approximately two thirds of the samples. The median Class I and II MFI decrease among the responding samples was 16.7% and 14%, respectively (p<0.05). HLA Matchmaker analysis of the patients' class I epitope sequences revealed apparent amino-acid differences between the patterns of the responding and non-responding patients.

CONCLUSION

In vitro incubation of sera in the presence of AS101 causes a decrease in the anti-HLA Ab's reactivity in several patient samples. Sera most likely to demonstrate this effect are characterized by a moderate MFI level and a distinct antibody reactivity pattern specific for defined HLA antigen epitopes. These results support further investigation of AS101 as a potential agent for desensitization of humoral reactivity prior to transplantation.

A personal perspective: 100-year history of the humoral theory of transplantation

The humoral theory states that antibodies cause the rejection of allografts. From 1917 to 1929, extensive efforts were made to produce antibodies against tumors. It was finally realized that the antibodies were produced against the transplant antigens present on transplantable tumors, not against the tumor-specific antigens. To get around this problem, inbred mouse strains were developed, leading to identification of the transplant antigens determined by the H-2 locus of mice. The antibodies were hemagglutinating and cytotoxic antibodies. The analogous human leukocyte antigen system was established by analysis of lymphocytotoxic alloantibodies that were made by pregnant women, directed against mismatched antigens of the fetus. The human leukocyte antigen antibodies were then found to cause hyperacute rejection, acute rejection, and chronic rejection of kidneys. Antibodies appeared in almost all patients after rejection of kidneys. With Luminex single antigen bead technology, donor-specific antibodies could be identified before rise in serum creatinine and graft failure. Antibodies were shown to be predictive of subsequent graft failure in kidney, heart, and lung transplants: patients without antibodies had superior 4-year graft survival compared with those who did have antibodies. New evidence that antibodies are also associated with chronic failure has appeared for liver and islet transplants. Four studies have now shown that removal or reduction of antibodies result in higher graft survival. If removal of antibodies prevents chronic graft failure, final validation of the humoral theory can be achieved.

Durability of antibody removal following proteasome inhibitor-based therapy

BACKGROUND

Evidence of the short-term effect of bortezomib on donor-specific human leukocyte antigen (HLA) antibody (DSA) removal capacity has emerged. However, no published data characterize the durability of DSA response. Here, we report the long-term DSA response results on renal transplant patients treated with bortezomib.

METHODS

In this single-center study, 26 living-donor renal transplant patients with a positive level of de novo DSA were preemptively treated with bortezomib (1.3 mg/m × 4 doses). A total of 15 patients received bortezomib as part of a combination regimen; 11 received bortezomib alone. Weekly serial measurements of HLA antibody were noted before, during, and after treatment using single-antigen beads.

RESULTS

At a median follow-up of 25.8 months posttreatment, allograft function remained good in each of the patients. Following treatment, 96% of the patients achieved at least a partial response. Eighteen patients (69%) experienced a complete response followed by a period of DSA remission. Ten patients had DSA relapse after remission, at a median of 3.8 months. The remaining eight patients are still in remission at 14 months posttreatment (median). Patients with remission enjoyed better allograft functional stability than those who relapsed (P=0.023). After bortezomib therapy, the addition of a calcineurin inhibitor or mycophenolate mofetil was predictive for maintaining a DSA remission (hazard ratio 0.09, 95% confidence interval 0.01-0.76).

CONCLUSIONS

Bortezomib therapy consistently provides reduction in DSA and in many a DSA remission may occur. However, sustaining remission is likely necessary to improve allograft stability.

Antibody-mediated kidney allograft rejection: therapeutic options and their experimental rationale

With the advent of novel therapies to directly intervene with B cell immunity and complement activation, antibody-mediated kidney allograft rejection (AMR) has come into the focus of transplant immunologists. Intravenous immunoglobulin, rituximab, bortezomib, and eculizumab have been used to treat patients with acute AMR, apart from the standard treatment of antibody removal with plasma exchange or immunoadsorption and steroid pulses. This article describes the experimental rationale and summarizes the still limited clinical experience with these novel therapies in the transplant setting. Results with the standard treatment for acute AMR, including intense plasmapheresis, intravenous immunoglobulins, and steroids are good with a graft survival of 80% at 18 months. In contrast, patients suffering from chronic AMR have significant irreversible damage in their grafts with substantially impaired graft survival. Thus, the authors propose a step-wise escalation of therapy in refractory cases of acute AMR and advocate an urgent need for controlled therapeutic trials for acute and chronic AMR not to inflict unnecessary harm on our patients by uncontrolled polypragmasy.

The state of therapy for removal of alloantibody producing plasma cells in transplantation

The current evidence clearly points towards donor specific alloantibody as a major cause of allograft loss. In order to mitigate allograft loss due to antibodies, treating the source of antibody production, the plasma cell is essential. Therapies that lack effect on the terminally differentiated (long-lived) plasma cell, such as rituximab, intravenous immune globulin and, plasmapheresis were the therapies used prior to 2007. In studies, their ability to remove antibody was found to be incomplete and/or cost prohibitive. In 2007, a proteasome inhibitor, bortezomib, was used for the first time in transplant due to its ability to deplete plasma cells. Through multiple case reports it has demonstrated consistent success in DSA reduction and removal, with only a few reports of failure to date. This review discusses the plasma cell, the alloantibody, and the current data supporting proteasome inhibitor use in transplant.

Terminal complement inhibition decreases antibody-mediated rejection in sensitized renal transplant recipients

Sensitized renal transplant recipients with high levels of donor-specific alloantibody (DSA) commonly develop antibody-mediated rejection (AMR), which may cause acute graft loss or shorten allograft survival. We examined the efficacy of terminal complement inhibition with the humanized anti-C5 antibody, eculizumab, in the prevention AMR in renal transplant recipients with a positive crossmatch against their living donor. The incidence of biopsy-proven AMR in the first 3 months posttransplant in 26 highly sensitized recipients of living donor renal transplants who received eculizumab posttransplant was compared to a historical control group of 51 sensitized patients treated with a similar plasma exchange (PE)-based protocol without eculizumab. The incidence of AMR was 7.7% (2/26) in the eculizumab group compared to 41.2% (21/51) in the control group (p = 0.0031). Eculizumab also decreased AMR in patients who developed high levels of DSA early after transplantation that caused proximal complement activation. With eculizumab, AMR episodes were easily treated with PE reducing the need for splenectomy. On 1-year protocol biopsy, transplant glomerulopathy was found to be present in 6.7% (1/15) eculizumab-treated recipients and in 35.7% (15/42) of control patients (p = 0.044). Inhibition of terminal complement activation with eculizumab decreases the incidence of early AMR in sensitized renal transplant recipients (ClincalTrials.gov number NCT006707).

Evaluation of the highly sensitized transplant recipient

The immune response against alloantigens involves the production of antibodies and development of T-cell immunity. Recipients sensitized to HLA antigens may have antibodies to almost all donors and may not be able to find a suitable kidney transplant donor. Strategies available to enable these patients to obtain a transplant are to give priority to highly sensitized patients, to perform therapy for antibody reduction or to transplant with existing antibodies and to intervene as needed with post-transplant treatment. While sensitization against HLA antigens is the most important cause of immunological transplant failure, other types of alloantigens, many of them expressed selectively in endothelial cells, and autoantigens may also be involved. Molecular typing and solid-phase antibody testing have markedly changed this field in the last few years. Methods for the analysis of HLA antibodies and for the study of T-cell reactivity and sensitization will also be discussed. Virtual cross-matching can now be performed for many patients, resulting in considerable savings in time and effort. Successful application of this approach requires the intervention of highly trained personnel with a good understanding of the limitations of the procedure and with intimate knowledge of the antibody profiles of the patients on the waiting list.

Guidelines for the diagnosis of antibody-mediated rejection in pancreas allografts-updated Banff grading schema

The first Banff proposal for the diagnosis of pancreas rejection (Am J Transplant 2008; 8: 237) dealt primarily with the diagnosis of acute T-cell-mediated rejection (ACMR), while only tentatively addressing issues pertaining to antibody-mediated rejection (AMR). This document presents comprehensive guidelines for the diagnosis of AMR, first proposed at the 10th Banff Conference on Allograft Pathology and refined by a broad-based multidisciplinary panel. Pancreatic AMR is best identified by a combination of serological and immunohistopathological findings consisting of (i) identification of circulating donor-specific antibodies, and histopathological data including (ii) morphological evidence of microvascular tissue injury and (iii) C4d staining in interacinar capillaries. Acute AMR is diagnosed conclusively if these three elements are present, whereas a diagnosis of suspicious for AMR is rendered if only two elements are identified. The identification of only one diagnostic element is not sufficient for the diagnosis of AMR but should prompt heightened clinical vigilance. AMR and ACMR may coexist, and should be recognized and graded independently. This proposal is based on our current knowledge of the pathogenesis of pancreas rejection and currently available tools for diagnosis. A systematized clinicopathological approach to AMR is essential for the development and assessment of much needed therapeutic interventions.

Inferior kidney allograft outcomes in patients with de novo donor-specific antibodies are due to acute rejection episodes

BACKGROUND

Donor-specific antibodies (DSAs) after kidney transplantation have been associated with poor graft outcomes in multiple studies. However, these studies have generally used stored sera or a single cross sectional screening test to identify patients with DSA. We evaluated the effectiveness of a prospective DSA screening protocol in identifying kidney and kidney/pancreas recipients at risk for poor graft outcomes.

METHODS

From September 2007 through September 2009, 244 consecutively transplanted kidney and kidney/pancreas recipients without pretransplant DSA were screened for de novo DSA at 1, 6, 12, and 24 months and when clinically indicated.

RESULTS

DSA was detected in 27% of all patients by protocol or indication screening. Patients with DSA (DSA+) were significantly more likely to have experienced acute rejection (AR) compared with no DSA (DSA-) (29% vs. 9.5%, P<0.001), and lower estimated 2-year graft survival (83% vs. 98%, P<0.001). Only 3 of 19 DSA (+) patients with AR had DSA detected before the AR episode. When excluding patients with AR, 2-year graft survival was similar between DSA (+) and DSA (-) patients (100% vs. 99%) as was estimated glomerular filtration rate. Patients with DSA detected by protocol screening had similar outcomes compared with DSA (-), whereas those with DSA detected by indication experienced significantly worse outcomes.

CONCLUSIONS

Patients with de novo DSA experience worse graft outcomes due to previous/concurrent episodes of AR. A prospective DSA screening protocol failed to identify patients at risk for AR or poor short-term graft outcomes.

Summary of FDA antibody-mediated rejection workshop

The Food and Drug Administration (FDA) held an open public workshop in June 2010 to discuss the current state of science related to antibody-mediated rejection (AMR) in kidney transplantation. Desensitization, acute AMR and chronic AMR (CAMR) were considered in the context of clinical trial design. Participants discussed experiences with HLA antibody detection and quantitation and the utility of monitoring donor-specific antibodies (DSAs) to inform the management of patients with AMR. The role for animal models was discussed. Diagnostic and prognostic features of histology were presented, followed by discussion of sensitivity and specificity of various criteria. The published literature on treatment of acute AMR was summarized, which consisted of case series and limited data from controlled clinical trials. Considerations for future clinical trials were presented, including endpoints and statistical evaluations of outcome. Although many issues need further consideration, the meeting enabled an important exchange of ideas between experts in the field.

The strength of donor-specific antibody is a more reliable predictor of antibody-mediated rejection than flow cytometry crossmatch analysis in desensitized kidney recipients

The aim of this study was to evaluate the utility of donor-specific antibodies (DSA) and flow cytometry crossmatch (FCCM) as tools for predicting antibody-mediated rejection (AMR) in desensitized kidney recipients. Sera from 44 patients with DSA at the time of transplant were reviewed. Strength of DSA was determined by single antigen Luminex bead assay and expressed as mean fluorescence intensity (MFI). T- and B-cell FCCM results were expressed as mean channel shift (MCS). AMR was diagnosed by C4d deposition on biopsy. Incidence of early AMR was 31%. Significant differences in the number of DSAs (p = 0.0002), cumulative median MFI in DSA class I (p = 0.0004), and total (class I + class II) DSA (p < 0.0001) were found in patients with and without AMR. No significant difference was seen in MCS of T and B FCCM (p = 0.095 and p = 0.307, respectively). The three-yr graft survival in desensitized patients with DSA having total MFI < 9500 was 100% compared to 76% with those having total MFI > 9500 (p = 0.022). Desensitized kidney transplant recipients having higher levels of class I and total DSA MFI are at high risk for AMR and poor graft survival. Recipient DSA MFI appears to be a more reliable predictor of AMR than MCS of FCCM.