Overcoming a Positive Crossmatch in Living-Donor Kidney Transplantation

Many patients who have an otherwise acceptable living-kidney donor do not undergo transplantation because of the presence of antibodies against the donor cells resulting in a positive crossmatch. In the current study, 14 patients with a positive cytotoxic crossmatch (titer 相似文献   

Peritransplant Immunoadsorption for Positive Crossmatch Deceased Donor Kidney Transplantation

Various desensitization protocols were shown to enable successful living donor kidney transplantation across a positive complement‐dependent cytotoxicity crossmatch (CDCXM). Positive crossmatch transplantation, however, is less well established for deceased donor transplantation. We report a cohort of 68 deceased donor renal allograft recipients who, on the basis of broad sensitization (lymphocytotoxic panel reactivity ≥40%), were subjected to a protocol of peritransplant immunoadsorption (IA). Treatment consisted of a single session of immediate pretransplant IA (protein A) followed by posttransplant IA and antilymphocyte antibody therapy. Twenty‐one patients had a positive CDCXM, which could be rendered negative by pretransplant apheresis. Solid phase HLA antibody detection revealed preformed donor‐specific antibodies (DSA) in all 21 CDCXM‐positive and in 30 CDCXM‐negative recipients. At 5 years, overall graft survival, death‐censored graft survival and patient survival were 63%, 76% and 87%, respectively, without any differences between CDCXM‐positive, CDCXM‐negative/DSA‐positive and CDCXM‐negative/DSA‐negative recipients. Furthermore, groups did not differ regarding rates of antibody‐mediated rejection (24% vs. 30% vs. 24%, p = 0.84), cellular rejection (14% vs. 23% vs. 18%, p = 0.7) or allograft function (median 5‐year serum creatinine: 1.3 vs. 1.8 vs. 1.7 mg/dL, p = 0.62). Our results suggest that peritransplant IA is an effective strategy for rapid desensitization in deceased donor transplantation.     

Virtual Crossmatch Approach to Maximize Matching in Paired Kidney Donation

We developed and tested a new computer program to match maximal sets of incompatible live donor/recipient pairs from a national paired kidney donation (PKD) registry. Data of 32 incompatible pairs included ABO and 4 digit‐high‐resolution donor and recipient HLA antigens and recipient's HLA antibodies. Three test runs were compared, in which donors were excluded from matching to recipients with either donor‐specific antibodies (DSA) >8000MFI (mean fluorescent intensity) at low‐resolution (Run 1) or >8000MFI at high‐resolution (Run 2) or >2000MFI and high‐resolution (Run 3). Run 1 identified 22 703 possible combinations, with 20 pairs in the top ranked, Run 2 identified 24 113 combinations, with 19 pairs in the top ranked and Run 3 identified 8843 combinations, with 17 pairs in the top ranked. Review of DSA in Run 1 revealed that six recipients had DSA 2000–8000MFI causing a possible positive crossmatch resulting in breakdown of two 3‐way and three 2‐way chains. In Run 2, four recipients had DSA 2000–8000MFI, also potentially causing breakdown of three 2‐way chains. The more prudent approach of excluding from matching recipients with DSA with >2000MFI reduces the probability of matched pairs having a positive crossmatch without significantly decreasing the number of possible transplants.     

Renal Transplantation With Final Allocation Based on the Virtual Crossmatch

Solid phase immunoassays (SPI) are now routinely used to detect HLA antibodies. However, the flow cytometric crossmatch (FCXM) remains the established method for assessing final donor–recipient compatibility. Since 2005 we have followed a protocol whereby the final allocation decision for renal transplantation is based on SPI (not the FCXM). Here we report long‐term graft outcomes for 508 consecutive kidney transplants using this protocol. All recipients were negative for donor‐specific antibody by SPI. Primary outcomes are graft survival and incidence of acute rejection within 1 year (AR <1 year) for FCXM+ (n = 54) and FCXM? (n = 454) recipients. Median follow‐up is 7.1 years. FCXM+ recipients were significantly different from FCXM? recipients for the following risk factors: living donor (24% vs. 39%, p = 0.03), duration of dialysis (31.0 months vs. 13.5 months, p = 0.008), retransplants (17% vs. 7.3%, p = 0.04), % sensitized (63% vs. 19%, p = 0.001), and PRA >80% (20% vs. 4.8%, p = 0.001). Despite these differences, 5‐year actual graft survival rates are 87% and 84%, respectively. AR <1 year occurred in 13% FCXM+ and 12% FCXM? recipients. Crossmatch status was not associated with graft outcomes in any univariate or multivariate model. Renal transplantation can be performed successfully, using SPI as the definitive test for donor–recipient compatibility.     

Kidney Transplantation Across a Positive Crossmatch: A Single-Center Experience

Background

Kidney transplantation is the treatment of choice for end-stage renal disease, with improved mortality and quality of life compared with dialysis. Desensitization protocols have allowed kidney transplantation of highly sensitized patients, who have a lower probability to receive a matching kidney from a deceased or living donor. The aim of this work was to analyze the post-transplantation period of highly HLA-sensitized patients with positive flow cytometry crossmatch against donor cells.

Methods

Following an observational, retrospective design, we investigated 16 highly sensitized patients who underwent kidney or kidney-pancreas transplantation, assessing the impact of desensitization protocols and investigating treatment-related complications, graft function, antibody-mediated rejection (AMR) rate, and graft and patient survivals.

Results

We studied 16 patients with positive flow cytometry crossmatch, who were divided into 2 groups based on whether they were submitted to a desensitization protocol or not. Patients who were desensitized underwent transplantation in later years, had higher immunologic risk (panel reactive antibody peak 62% vs 33%; P = .038), higher percentage of 2nd kidney transplant (75% vs 25%; P = .066), and higher percentage of donor-specific anti-HLA antibodies identified (P = .028). A majority of patients were desensitized with high-dose intravenous immunoglobulin and plasmapheresis, and 5 patients received rituximab. Acute AMR rate was of 38%, and rituximab was associated with fewer episodes of AMR. Only 1 patient had graft failure, due to chronic humoral rejection, and the remaining maintained good graft function (mean serum creatinine value of 1.33 mg/dL). No patient died and few complications related to immunossupression were observed.

Conclusions

Desensitization protocols were safe and allowed kidney transplantation in highly sensitized patients that probably would never undergo transplantation and gave the opportunity of living-donor transplant to patients with anti-HLA antibodies against the donor.     

Alloantibody Levels and Acute Humoral Rejection Early After Positive Crossmatch Kidney Transplantation

We examined the course of donor ‐ specific alloantibody (DSA) levels early after transplant and their relationship with acute humoral rejection (AHR) in two groups of positive crossmatch (+XM) kidney transplant recipients: High DSA group—41 recipients with a baseline T‐ or B‐cell flow crossmatch (TFXM, BFXM) channel shift ≥300 (molecules of equivalent soluble fluorochrome units (MESF) of approximately 19 300) who underwent pretransplant plasmapheresis (PP), and Low DSA group—29 recipients with a baseline channel shift <300 who did not undergo PP. The incidence of AHR was 39% (16/41) in the High DSA group and 31% (9/29) in the Low DSA group. Overall, mean DSA levels decreased by day 4 posttransplant and remained low in patients who did not develop AHR. By day 10, DSA levels increased in patients developing AHR with 92% (23/25) of patients with a BFXM >359 (MESF of approximately 34 000) developing AHR. The BFXM and the total DSA measured by single antigen beads correlated well across a wide spectrum suggesting that either could be used for monitoring. We conclude that AHR is associated with the development of High DSA levels posttransplant and protocols aimed at maintaining DSA at lower levels may decrease the incidence of AHR.     

Baseline Donor‐Specific Antibody Levels and Outcomes in Positive Crossmatch Kidney Transplantation

Renal transplant candidates with donor‐specific alloantibody (DSA) have increased risk of antibody‐mediated allograft injury. The goal of this study was to correlate the risk of antibody‐mediated rejection (AMR), transplant glomerulopathy (TG) and graft survival with the baseline DSA level (prior to initiation of pretransplant conditioning). These analyses include 119 positive crossmatch (+XM) compared to 70 negative crossmatch (?XM) transplants performed between April 2000 and July 2007. Using a combination of cell‐based crossmatch tests, DSA level was stratified into very high +XM, high +XM, low +XM and ?XM groups. In +XM transplants, increasing DSA level was associated with increased risk for AMR (HR = 1.76 [1.51, 2.07], p = 0.0001) but not TG (p = 0.18). We found an increased risk for both early and late allograft loss associated with very high DSA (HR = 7.71 [2.95, 20.1], p = 0.0001). Although lower DSA recipients commonly developed AMR and TG, allograft survival was similar to that of ?XM patients (p = 0.31). We conclude that the baseline DSA level correlates with risk of early and late alloantibody‐mediated allograft injury. With current protocols, very high baseline DSA patients have high rates of AMR and poor long‐term allograft survival highlighting the need for improved therapy for these candidates.     

Histologic Findings One Year After Positive Crossmatch or ABO Blood Group Incompatible Living Donor Kidney Transplantation

Recent protocols have allowed successful positive crossmatch (+XM) and ABO incompatible (ABOI) kidney transplantation, although their long-term outcome is not clear. To begin to assess this issue we compared protocol biopsies performed 12 months posttransplant in 37 +XM, 24 ABOI and 198 conventional allografts. Although the majority in all three groups had only minimal histologic changes, transplant glomerulopathy (TG) was significantly increased in +XM (22% vs. 13% ABOI vs. 8% conventional, p = 0.015), and correlated with prior humoral rejection (HR) by multivariate analysis (odds ratio 17.5, p < or = 0.0001). Patients with a prior history of HR also had a significant increase in interstitial fibrosis (No HR 54% vs. HR 86%, p = 0.045). In the absence of HR no difference in histologic changes was seen between groups, although all three groups had a demonstrable mild increase in interstitial fibrosis from biopsies performed at the time of transplant. Thus, although HR is associated with an increase in TG, in its absence allograft histology is similar in +XM, ABOI and conventional allografts 1 year posttransplant.     

Virtual Crossmatch: Reality of Perception

Results of 773 actual flow crossmatches (aFXMs) and virtual flow crossmatches (vFXMs) performed for living and deceased donor kidney transplantation in our center were analyzed retrospectively and evaluated for their concordance. Prediction of vFXMs was based on antibody identification using single antigen bead assay and locally established mean fluorescence intensity cutoff point compared with donor HLA antigens. The vast majority of aFXMs were in concordance with vFXMs with an overall concordance of 97%. Twenty-three predicted to be negative showed positive aFXMs; 12 of them had 0% calculated panel-reactive antibody, and 11 were found in patients with multiple non?donor-specific HLA antibodies. Three predicted positive vFXMs yielded negative aFXMs; 2 of them had allele-specific antibodies.

Virtual Crossmatching in Kidney Transplantation: The Wait Is Over

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Five‐Year Outcomes in Living Donor Kidney Transplants With a Positive Crossmatch

Renal transplant candidates with high levels of donor‐specific anti‐HLA antibodies have low transplantation rates and high mortality rates on dialysis. Using desensitization protocols, good short‐term outcomes are possible in “positive crossmatch kidney transplants (+XMKTx)”, but long‐term outcome data are lacking. The aim of the current study was to determine actual 5‐year graft outcomes of +XMKTx. We compared graft survival and the functional and histologic status of 102 +XMKTx to 204 ?XMKTx matched for age and sex. Actual 5‐year death‐censored graft survival was lower in the +XMKTx group (70.7% vs. 88.0%, p < 0.01) and chronic injury (glomerulopathy) was present in 54.5% of surviving grafts. Graft survival was higher in recipients with antibody against donor class I only compared with antibody against class II (either alone or in combination with class I) (85.3% vs. 62.6%, p = 0.05) and was similar to ?XMKTx (85.3 vs. 88.0%, p = 0.64). Renal function and proteinuria ranged across a wide spectrum in all groups reflecting the different histological findings at 5 years. We conclude that when compared to ?XMKTx, +XMKTx have inferior outcomes at 5 years, however, almost half of the surviving grafts do not have glomerulopathy and avoiding antibodies against donor class II may improve outcomes.     

Maintaining Equity and Access: Successful Implementation of a Virtual Kidney Transplantation Evaluation

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Impact of Flow Cytometry Crossmatch B-Cell Positivity on Living Renal Transplantation

Background

Various studies have reported poorer graft survival among individuals displaying T-cell-positive flow cytometry crossmatches (FCXM). Good outcomes have been observed in immunologically high-risk patients with the use of rituximab, plasmapheresis, and γ-globulin. Because the relevance of FCXM B-cell–positivity (BCXM (+)) alone remains controversial, we examined its impact on living donor renal transplantations.

Patients and Methods

We retrospectively studied 146 adult renal transplantation recipients from April 2007 to June 2012, dividing the patients into BCXM (+) (n = 31) versus BCXM (−) recipients (n = 115). We examined patient and graft survivals as well as rejection rates at 0 to 3, 3 to 12, and 12 to 24 months. We also determined the incidence of infectious diseases. We performed stepwise multivariate regression to identify risk factors contributing rejection episodes.

Results

One-year patient and graft survivals were 100% in both groups. The BCXM (−) group have a 16.8% rejection probability whereas the BCXM (+) group, 33.2% (P = .201). There were no significantly differences in the incidence of infectious diseases. Only the rate of a sensitizing history was an independent risk factor for a rejection episode.

Conclusion

BCXM (+) showed only a tendency but not a significant impact on rejection episodes compared with BCXM (−); short-term graft survivals were similar.