American Journal of Transplantation 2009; 9: 1063–1071 Wiley Periodicals Inc.
C 2009 The Authors C 2009 The American Society of Journal compilation Transplantation and the American Society of Transplant Surgeons
doi: 10.1111/j.1600-6143.2009.02577.x
Reducing De Novo Donor-Specific Antibody Levels during Acute Rejection Diminishes Renal Allograft Loss M. J. Everlya, ∗ , J. J. Everlya , L. J. Arendc , P. Braileyb , B. Susskindb , A. Govild , A. Rikea , P. Roy-Chaudhuryd , G. Mogilishettyd , R. R. Allowayd , A. Tevara and E. S. Woodlea, ∗ a Department of Surgery, Transplantation Division, University of Cincinnati College of Medicine, Cincinnati, OH b Hoxworth Blood Center, Cincinnati, OH c Department of Pathology, University of Cincinnati College of Medicine, Cincinnati, OH d Department of Internal Medicine, Division of Nephrology, University of Cincinnati College of Medicine, Cincinnati, OH ∗ Corresponding author: E. Steve Woodle,
[email protected] Funding sources: None Conflicts of interest: None (for all authors)
The effect of de novo DSA detected at the time of acute cellular rejection (ACR) and the response of DSA levels to rejection therapy on renal allograft survival were analyzed. Kidney transplant patients with acute rejection underwent DSA testing at rejection diagnosis with DSA levels quantified using Luminex single-antigen beads. Fifty-two patients experienced acute rejection with 16 (31%) testing positive for de novo DSA. Median follow-up was 27.0 ± 17.4 months postacute rejection. Univariate analysis of factors influencing allograft survival demonstrated significance for African American race, DGF, cytotoxic PRA >20% (current) and/or >50% (peak), de novo DSA, C4d and repeat transplantation. Multivariate analysis showed only de novo DSA (6.6fold increased allograft loss risk, p = 0.017) to be significant. Four-year allograft survival was higher with ACR (without DSA) (100%) than mixed acute rejection (ACR with DSA/ C4d) (65%) or antibody-mediated rejection (35%) (p < 0.001). Patients with >50% reduction in DSA within 14 days experienced higher allograft survival (p = 0.039). De novo DSAs detected at rejection are associated with reduced allograft survival, but prompt DSA reduction was associated with improved allograft survival. DSA should be considered a potential new end point for rejection therapy. Key words: Antihumoral therapy, allograft survival, antibody-mediated rejection, donor-specific antibodies, C4d, mixed acute rejection Received 15 August 2008, revised 18 December 2008 and accepted for publication 09 January 2009
Introduction Assays for diagnosing humoral responses (single-antigen bead donor-specific HLA antibody (DSA) analysis and complement split product (C4d) detection via immunohistochemistry) have provided a means for examining the role of humoral immunity in acute and chronic rejection (1–3). Current rejection therapies remain focused primarily on T-lymphocytes, and therapeutic success is defined solely on renal allograft function and histology. We have hypothesized that chronic rejection and late allograft loss may result, at least in part, from failure to recognize and inadequately treat the allospecific humoral immune responses when present during acute rejection. In this scenario, longterm persistence of humoral alloresponses after successful treatment of cellular rejection results in ongoing renal allograft injury. As a first step in evaluating this hypothesis, we analyzed renal allograft recipients with acute rejection episodes for evidence of DSA (at the time of acute rejection) over a 5-year period. In addition to analyzing the traditionally recognized entities of acute cellular rejection (ACR) and antibody-mediated rejection (AMR), we evaluated a new entity mixed acute rejection (MAR). Mixed acute rejection was defined as acute rejection episodes accompanied by de novo DSA and/or C4d staining detected at the time of acute rejection diagnosis. Allograft survival was compared in patients with ACR, AMR and MAR. In addition, the effect of antirejection therapies on DSA levels was correlated with long-term renal allograft survival. The hypothesis to be tested in this study was that donorspecific humoral responses present at the time of acute rejection are an important predictor of long-term renal allograft survival. We also evaluated a corollary to this hypothesis: failure to promptly recognize and effectively treat humoral donor-specific immune responses at the time of acute rejection is associated with reduced long-term renal allograft survival.
Methods Patient selection and characteristics Kidney transplant recipients who received a transplant at the University Hospital and Christ Hospital in Cincinnati and experienced acute rejection between January 1, 2003, and October 1, 2007, were analyzed.
Renal allograft biopsy Acute rejection was defined as an increase in serum creatinine (SCr) at least 20% above baseline SCr with histologic evidence of acute rejection
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Everly et al. Table 1: Demographic data, immunologic risk factors and acute rejection characteristics
Patient demographics Number of patients Mean age (years) Gender Male Female African American race Deceased donor organ Repeat transplant Delayed graft function Immunologic risk factors Pretransplant anti-HLA antibodies Current CDC PRA >20% and/or peak CDC PRA >50% at transplant Rejection characteristics Serum creatinine1 (mg/dL) Time to rejection (months)∗ C4d positive rejection episodes Diffuse C4d Focal C4d Follow-up (months) From transplant Mean ± SD Median From rejection Mean ± SD Median
ACR N (%)
AMR N (%)
Mixed N (%)
Unclassified N (%)
p-Value
30 45.5 ± 11.6
10 44.7 ± 13.8
12 36.1 ± 10.7
42 44.8 ± 13.6
NS
21 (70) 9 (30) 10 (33) 11 (44) 0 (0) 0 (0)
3 (30) 7 (70) 7 (70) 6 (39) 2 (10) 2 (10)
6 (50) 6 (50) 5 (42) 4 (33) 4 (33) 2 (10)
30 (71) 12 (29) 10 (24) 19 (45) 5 (12) 6 (14)
NS NS NS NS
0 (0) 0 (0)
0 (0) 3 (30)
0 (0) 1 (8)
0 (0) 6 (14)
NS NS
3.21 ± 2.90 3.6 ± 9.9 0 (0) 0 0
3.21 ± 1.72 4.9 ± 7.7 10 (100) 5 5
3.25 ± 3.31 9.0 ± 9.3 9 (75) 3 6
3.19 ± 1.71 16.4 ± 16.2 – – –
NS 0.001 NS NS NS
39.4 ± 17.0 41.6
21.6 ± 14.1 21.0
31.0 ± 17.8 28.9
41.6 ± 22.0 46.4
0.020
35.6 ± 16.3 35.5
16.7 ± 14.8 11.8
23.7 ± 18.0 24.6
25.2 ± 21.1 21.4
0.022
NS
CDC = complement-dependent cytotoxicity; PRA = panel reactive antibody; MMF = mycophenolate mofetil; NS = not statistically significant (p > 0.05). 1 Estimate based on the 5 SCr measurements immediately preceding rejection.
defined on renal allograft biopsy by Banff 1997 criteria (update 2003) (4,5). Baseline SCr was defined as the mean of the 5 consecutive SCr measurements immediately preceding acute rejection diagnosis. Per Banff criteria, renal allografts were considered consistent with AMR if the two out of the three following characteristics were present: donor-specific anti-HLA antibody (DSA), histologic changes consistent with AMR and positive C4d staining in peritubular capillaries ± other structures are present (4). Mixed rejection (mixed) was defined as ACR with positive DSA and/or positive C4d immunohistochemistry. Patients achieving rejection reversal were defined as those with histologic resolution or SCr decrease to within 115% of baseline.
(MESF) using a standard curve generated with Quantum TM 27 microbeads (Bangs Laboratories Inc., Fishers, IN). DSA was considered positive when its specificity value (MESF) was ≥3 times the autologous HLA antigens’ MESF. All DSAs were de novo, i.e. not detected before kidney transplant. Immunodominant DSA (iDSA) was defined as DSA with highest level (expressed as molecules of equivalent soluble fluorescence) and nonimmunodominant DSA was defined as donor-specific anti-HLA antibodies at lower levels than iDSA.
Graft outcome Graft failure was defined as a return to dialysis.
C4d staining was performed by immunohistochemistry on paraffin sections using a rabbit polyclonal antibody specific for human C4d (C4dpAb; Alpco Diagnostics, Windham, NH) using a Ventana Benchmark automated stainer (Ventana Medical Systems, Inc., Tucson, AZ) and horseradish peroxidasediaminobenzidine detection. Hematoxylin was used as counterstain. C4d staining in peritubular capillaries was considered to be positive if linear circumferential peritubular capillary staining was identified in greater than 50% of peritubular capillaries, excluding scarred or necrotic areas. C4d staining of glomerular capillaries was considered positive if multiple glomeruli were noted to have multiple capillary loops with linear C4d staining.
Detection of donor-specific antibody Donor-specific anti-HLA antibodies (DSAs) were identified using antigen bead panels by Luminex assay (LABScreen TM, One Lambda Inc., Canoga Park, CA). Fluorescence intensity values obtained from the Luminex platform were converted to molecules of equivalent soluble fluorescence
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Data collection and statistical analysis Data collected included donor–recipient sex, race, age, current and peak serologic panel reactive antibody (PRA), primary or repeat transplant recipient, delayed graft function (DGF), donor kidney source (living or cadaveric donor), HLA matching (DR, A and B), mean baseline SCr >2 mg/dL, de novo anti-HLA antibody, and peritubular deposition of complement split product, C4d. Frequency tables were used to summarize the counts of each variable by DSA status. Normally distributed variables are expressed as mean ± standard deviation (SD), and nonnormally distributed variables are expressed as mean or median and range. Observations between groups were compared using the Fisher’s exact test for categorical variables. One-way ANOVA or unpaired t-test was used for continuous variables. Time to event analyses was calculated by the Kaplan–Meier method and statistical significance determined by log rank test. Multiple comparisons were assessed
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Reducing DSA in Rejection Diminishes Allograft Loss
1.0
DSA ABSENT
0.9
(N = 38; 3 Allografts Lost)
Proportion of Allografts Surviving
0.8
0.7
0.6
0.5
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0.4
(N = 16; 7 Allografts Lost) 0.3
0.2
0.1
Figure 1: Kaplan–Meier survival in patients with or without DSA at rejection diagnosis (p = 0.001; log-rank).
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using the Bonferroni method. Two-sided p-values less than 0.05 were considered significant.
needed to prevent bias in the multivariate model. This rule originates from a Monte Carlo simulation done on a single data set by Peduzzi et al. (6). Because our analysis had less than 10 EPV, additional analyses (RELOGIT, Cambridge, MA) were conducted to ensure bias was not present (6–8). Stepwise model selection method was used to arrive at a final regression model for determining independent predictors. Threshold of p = 0.05 was used for variable selection and for variable elimination. The final model was
Univariate and multivariate logistic regression analyses Variables with a significance level of p < 0.15 in the univariate logistic regression were selected for inclusion in multivariate logistic regression model. Ten events per variable (EPV) is a long-standing and loosely held guideline
ACR
1.0
(N = 30, NO Allografts Lost)
Proportion of Allografts Surviving
0.8
UNCLASSIFIED (N = 42, 7 Allografts Lost) 0.6
MIXED (N = 12, 4 Allografts Lost)
0.4
AMR (N = 10, 6 Allografts Lost) 0.2
Figure 2: Death-censored allograft survival stratified by rejection type (ACR vs. mixed (p < 0.001; log-rank), ACR vs. AMR (p < 0.001; log-rank) and unclassified vs. AMR (p < 0.001; logrank)).
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Proportion of Allografts Surviving
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0.7
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UNCLASSIFIED (N = 42; 7 Allografts Lost)
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Figure 3: Death-censored allograft survival stratified by classified or unclassified rejection type (p = 0.420; logrank).
assessed for goodness-of-fit. Statistical analyses were performed using the statistical package STATA/SE v9.2 (StataCorp, College Station, TX).
current CDC PRA >20%, peak CDC PRA >50%, C4d positivity and antibody-mediated rejection).
Results
The presence of donor-specific anti-HLA antibodies in acute rejection is associated with substantially reduced long-term renal allograft survival compared to ACR DSA presence at the time of acute rejection diagnosis was associated with increased renal allograft loss rates (Figure 1). Patients with DSA had a 5-year graft survival rate of 42 ± 16% as compared to 89 ± 6% in those without DSA (p = 0.0053). Of the three graft losses in patients without DSA, all cases were positive for C4d, suggesting that donor-specific non-HLA antibodies may have been responsible for allograft injury.
A total of 650 kidney transplant recipients were analyzed for acute rejection: 94 (15%) were identified with biopsyproven acute rejection by Banff criteria. Of these 94 kidney transplant recipients with biopsy-proven acute rejection, 52 were evaluated for DSA and C4d at the time of acute rejection diagnosis. Sixteen of 52 (31%) patients had DSA detected. The remaining 42 patients were biopsied early in the analysis period when routine DSA and C4d testing was first being implemented. As a result of slow implementation of this new policy, these patients did not have evaluations for DSA and C4d at the time of his/her rejection episode and therefore could not be included all analyses. These patients are referred to as ‘unclassified’ patients. Mean follow-up in patients with acute rejection was 29.2 ± 17.9 months and median follow-up 25.4 months was postacute rejection. Patient demographic, immunologic risk factors and rejection characteristics are presented in Table 1 and are classified by presence or absence of DSA at time of rejection diagnosis. Patients with DSA at rejection tended to be presensitized (higher incidence of repeat transplants, 1066
Allograft survival varied markedly depending on the type of acute rejection (Figure 2). Allograft loss did not occur in patients with pure ACR (i.e. ACR in the absence of DSA or C4d positivity). Patients with MAR experienced intermediate survival and patients with AMR experienced the lowest allograft survival rates. Survival differences between ACR and AMR were statistically significant (p < 0.001). The differences in allograft survival were also significant between patients with MAR and ACR (p < 0.001). No difference American Journal of Transplantation 2009; 9: 1063–1071
Reducing DSA in Rejection Diminishes Allograft Loss
1.0
0.9
Porportion of Allografts Surviving
0.8
0.7
iDSA Class I
0.6
iDSA Class II
(N = 7, 3 Allografts Lost)
(N = 9, 4 Allografts Lost)
0.5
0.4
0.3
0.2
0.1
0.0 Figure 4: Death-censored allograft survival stratified by iDSA class (p = 0.797; log-rank).
0
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was noted in death-censored allograft survival when stratifying by classified or unclassified rejection type (Figure 3) or class of iDSA at rejection (Figure 4).
DSA: An independent predictor of renal allograft loss Univariate analysis of risk factors for allograft loss showed recipient age and gender, donor age and race, donor type, AB mismatch and DR mismatch to be insignificant (Table 2). Six variables that were significantly associated with graft loss on univariate analysis included African American race, DGF, DSA, C4d, cytotoxic PRA >20% at transplant and repeat transplant. On multivariate analysis, DSA was the only significant factor for renal allograft loss (p = 0.017). Admitting, the resulting equation is somewhat ‘overfitted’ to the sample, and the estimates are associated with large standard errors as a result. Clearly, further studies are needed to determine the accuracy and durability of these estimates. Effective DSA reduction by antirejection therapy is associated with enhanced renal allograft survival Of the 16 patients with acute rejection and serial DSA titers, 10 had a 50% reduction in iDSA level at 14 days postacute reAmerican Journal of Transplantation 2009; 9: 1063–1071
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jection diagnosis. Median follow-up in these patients were 21.4 ± 17.1 months (Table 3). Rejection treatment did not significantly differ between groups (Tables 3 and 4). In addition no individual type of therapy (PP, IVIg, etc.) appeared more effective in reducing DSA. Patients with 50% reduction in iDSA (p = 0.039) (Figure 5). Median allograft survival was 27.9 months for pts with 50% reduction in iDSA, as renal allograft loss was not observed. DSA responses at day 14 are presented in Figure 6A and B.
Discussion Mixed acute rejection (MAR) is currently a largely unrecognized and incompletely treated entity in kidney transplant recipients. We consider MAR incompletely treated as standard anti-T-cell-targeted rejection therapies often have minimal influence on DSA levels. It is possible that the increased renal allograft loss observed in this study may have been due to long-term effects of DSA on the renal allograft. 1067
Everly et al. Table 2: Logistic regression analysis of risk factors for renal allograft loss v2
p-Value
Odds ratio
95% CI
0.02 0.98 5.70 0 0.39 1.02 0.83 1.31 2.49 3.97 2.49 0.24 6.09 5.67 0.36 1.04
0.887 0.335 0.030 1.000 0.526 0.314 0.367 0.266 0.102 0.041 0.102 0.631 0.017 0.016 0.536 0.285
0.900 0.969 6.533 1.000 1.680 2.109 1.479 0.443 5.857 6.667 5.860 0.659 6.600 7.800 0.567 2.785
0.211–3.827 0.911–1.032 1.203–35.478 0.942–1.061 0.338–8.347 0.493–9.019 0.632–3.461 0.106–1.859 0.705–48.676 1.084–40.975 0.705–48.676 0.120–3.612 1.392–31.283 1.468–41.418 0.094–3.408 0.425–18.226
Variable Recipient gender (male) Recipient age at transplant Recipient African American Donor age Donor African American Deceased donor kidney transplant AB mismatch DR mismatch CDC PRA current >20% and/or peak >50% Repeat transplant Delayed graft function Banff grade ACR ≥IIA DSA C4d Rejection reversal Repeat rejection
Multivariate stepwise logistic regression Variable
Coefficient (b)
Standard error
v2
p-Value
Odds ratio
95% CI
Intercept DSA
−2.397 1.887
0.603 0.794
– 6.09
– 0.017
– 6.6
– 1.392–31.283
C4d = diffuse C4d by immunohistochemistry; CDC = complement-dependent cytotoxicity; PRA = panel reactive antibody. Delayed graft function is defined as the need for at least one session of dialysis during the first 7 days after transplantation. Log∗(p/1 − p) = −2.397 + 1.887 ∗ DSA.
The presence of donor-reactive human leukocyte antigen (HLA)-specific antibodies following transplantation has been shown to be associated with poor transplant outcome (9–12). Likewise, AMR is associated with poor outcomes (4). Recent studies have indicated that DSA and C4d can be present during acute cellular rejection (i.e. mixed acute rejection) (13–15). Because mixed acute rejection is not a specific entity in Banff criteria, little is known about associated outcomes. In addition, despite DSA leading to poor outcomes, little information is available as to whether DSA levels correlate with rejection outcomes, or alternatively, whether DSA levels should be considered as end points for acute rejection therapy. Data presented in this report indicate that outcomes of acute rejection episodes are associated with the presence of DSA at the time of acute rejection. In addition, the data suggest that rapid DSA reduction during rejection therapy is associated with better long-term renal allograft survival.
DSA is an independent predictor of renal allograft loss Analysis of predictors of allograft loss revealed DSA to be an independent predictor of allograft loss when present during acute rejection, with a sixfold increase in allograft loss rates. This finding also indicates that DSA alone, and not C4d, predicted allograft loss. Recent studies have suggested that C4d is an imperfect predictor of allograft loss, especially when seen in late acute rejection (16). C4d has long been the key feature in patients with AMR, but our findings suggest that DSA detection is highly correlated with C4d staining; however, occasionally DSA are present in the absence of C4d staining on biopsy. Our observations 1068
suggest that DSAs alone are important, and may be worthy of therapeutic intervention, regardless of C4d status. These observations suggest that future prospective studies should focus on determining the relative importance of DSA and C4d testing in determining appropriate therapy for renal allograft rejection.
DSA reduction during acute rejection therapy The time point of 14 days for DSA reduction was arbitrarily chosen for this study, primarily because antirejection therapy is usually concluded between 7 and 14 days following institution of antirejection therapy. The 50% reduction threshold was chosen arbitrarily, primarily because anything less was thought to an insignificant. However, studies investigating further reduction or complete elimination of antibodies are necessary. Results from this study suggest that DSA reduction should receive consideration as a potential therapeutic goal for rejection therapy. If this observation proves to be correct, important additional questions will need to be answered including how fast and to what extent DSA reduction should be pursued to achieve improved outcomes. Our results indicate that a DSA reduction of at least 50% within 2 weeks of rejection diagnosis by biopsy is associated with improved allograft survival. It is also possible that serial DSA testing may be important following therapy to evaluate therapy response. These results argue that consideration be given to including defined DSA reductions in the definition of rejection reversal in addition to standard histologic and functional criteria. If DSA reduction does become established as a therapeutic goal in rejection therapy, it will likely provide a useful and objective American Journal of Transplantation 2009; 9: 1063–1071
Reducing DSA in Rejection Diminishes Allograft Loss Table 3: iDSA reduction data
Patient characteristics Number of patients Recipient age (years) Gender Male Female African American race Deceased donor organ Repeat transplant Delayed graft function Immunologic characteristics Pretransplant anti-HLA antibodies Current CDC PRA >20% at transplant Peak CDC PRA >50% at transplant Rejection characteristics Serum creatinine1 (mg/dL) Time to rejection (months)∗ Banff 97 grade (updated 2003) AMR IA/IB IIA–III DSA classes Class I Class II C4d positivity Diffuse C4d Focal C4d Mean DSA level at biopsy (MESF) Mean DSA level 14 days postbiopsy (MESF) Antirejection treatments Increase in maintenance immunosuppression R Thymoglobulin and/or pulse corticosteroids Plasmapheresis + intravenous immunoglobulin ± R R Rituxan (rituximab) ± Thymoglobulin Plasmapheresis and Thymoglobulin Increase in maintenance immunosuppression Follow-up (months) Follow-up posttransplant Mean ± SD Median Follow-up postrejection Mean ± SD Median
iDSA nonresponders 50% decrease N (%)
p-Value
10 43.9 ± 15.5
6 38.2 ± 11.2
NS
4 (40) 6 (60) 6 (40) 4 (40) 2 (20) 1 (10)
3 (50) 3 (50) 3 (50) 3 (50) 2 (33) 0 (0)
NS NS NS NS
0 (0) 2 (20) 2 (20)
0 (0) 2 (33) 2 (33)
NS NS NS
3.6 ± 3.1 8.8 ± 8.5
1.8 ± 0.8 6.9 ± 10.4
NS NS
7 (70) 2 (20) 1 (10)
2 (33) 4 (17) 0 (0)
NS NS NS
3 (30) 7 (70) 9 (90) 5 4 324 856 ± 232 990 336 495 ± 265 610
4 (67) 2 (33) 4 (67) 2 2 620 195 ± 437 472 181 931 ± 179 376
NS NS NS NS NS 0.048 NS
1 (10) 1 (10) 6 (60)
0 (0) 1 (17) 3 (50)
NS NS NS
2 (20) 1 (10)
2 (33) 0 (0)
NS NS
24.2 ± 15.6 21.0 (0.8–57)
32.3 ± 21.1 35.0 (5.6–54.0)
NS
15.4 ± 10.9 11.8 (0.2–34.7)
29.1 ± 22.4 28.8 (5.2–51.4)
NS
NS
1 Mean ±SD of the 5 consecutive serum creatinine (SCr) measurements immediately preceding rejection; NS = not statistically significant (p > 0.05).
Table 4: Acute rejection treatment
Increased baseline immunosuppression alone Antithymocyte globulin (rabbit) and/or pulse corticosteroids Plasmapheresis + antithymocyte globulin (rabbit) R Plasmapheresis + intravenous immunoglobulin ± Rituxan (rituximab) ± antithymocyte globulin (rabbit)
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ACR N (%)
AMR N (%)
Mixed N (%)
3 (10) 27 (90) 0 (0) 0 (0)
0 (0) 0 (0) 1 (10) 9 (90)
2 (17) 4 (33) 3 (25) 3 (25)
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iDSA Reduction > 50%
1.0
(N = 6; NO Allografts Lost) 0.9
Porportion of Allografts Surviving
0.8
0.7
0.6
0.5
0.4
0.3
0.2
iDSA Reduction < 50% (N = 10; 7 Allografts Lost)
0.1
Figure 5: Death-censored allograft survival stratified by % reduction in iDSA at 14 days postbiopsy (p = 0.021; log-rank).
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end point for evaluation of new antihumoral therapies. This change would be of major importance in the development of agents currently under development.
outcomes with mixed acute rejection are poor despite achievement of rejection reversal by traditional histologic criteria. This raises the possibility that suppression of DSA with antihumoral therapies may provide a means for improving long-term renal allograft survival. New anti-B-cell agents including those that specifically target the antibodyproducing cells (plasma cells), such as bortezomib, may provide effective means for reducing DSA levels and possibly minimizing renal allograft loss (17).
Conclusions Mixed acute rejection is an entity that is not recognized in current Banff criteria. The present study indicates that
Immunodominant DSA Level Responder Group
A.
Immunodominant DSA Level Non-Responders Group
B. 1400000
1400000 Pt #1 (Anti-A1) Pt #2 (Anti-DQ6) Pt #3 (Anti-B45) Pt #4 (Anti-DQ6) Pt #5 (Anti-B08) Pt #6 (Anti-B27)
1200000
1000000
Pt #1 (Anti-B44) Pt #2 (Anti-A24) Pt #3 (Anti-DR07) Pt #4 (Anti-DR11) Pt #5 (Anti-DQ07) Pt #6 (Anti-DQ02) Pt #7 (Anti-DR51) Pt #8 (Anti-DQ07) Pt #9 (Anti-DQ07) Pt#10 (Anti-A07)
1200000
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DSA Detection Threshold
600000
600000
400000
400000
200000
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0
0 Day 0 (Bx)
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Figure 6: iDSA levels at time of biopsy and 14 days after initiation of rejection therapy. (A) iDSA responders were primarily class I specific DSA and (B) iDSA nonresponders were predominantly class II specific DSA.
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