Recognition and Management of
Antibody-Mediated Rejection
Malcolm P. MacConmara, MB, BCh, BAO
Emory University School of Medicine, Atlanta, Georgia
A REPORT FROM THE 2013 AMERICAN TRANSPLANT CONGRESS
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1
Antibody-Mediated Rejection (AMR)

AMR is a major cause of acute and chronic allograft
dysfunction1,2
» Acute AMR occurs in at least 5%–7% of all kidney transplant
recipients and 25%–30% of presensitized crossmatchpositive patients.3
» Chronic AMR due to sensitization or de novo donor-reactive
antigen contributes to long-term allograft loss.2,4

AMR may result from reactivation of antibody
responses to preexisting antigens (type I) or de novo
to donor-specific antibodies (DSAs) encountered late
after transplant (type II), mostly as a result of
nonadherence to immunosuppressive therapy.5
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2
The Difficult Diagnosis of AMR

The current Banff classification of AMR relies upon
three cardinal features: (1) positive C4d staining,
(2) circulating DSA, and (3) tissue injury.

Histologic findings of injury vary.

Classification is based on clinical setting, underlying
pathophysiology, and temporal relationship to
transplantation (hyperacute, acute, and chronic).

Clinical manifestations range from immediate graft
loss to chronic subclinical rejection with gradual loss
of function.1–3
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Outcomes Associated with AMR

AMR has a worse outcome than acute cellular
rejection (ACR), likely because of diagnostic
difficulty and less-effective therapeutic options.

Among renal transplant recipients with AMR,
15%–20% lose their grafts within 1 year.6

More than 40% of patients with AMR eventually
develop transplant glomerulopathy, whether or not
initial treatment can reverse acute renal functional
impairment.

AMR-related glomerulopathy is associated with
< 50% 5-year graft survival from the time of
identification.6
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Targets and Therapies
Development of antibody-mediated rejection1
MMF = mycophenolate mofetil; TH cell = T-helper cell; IVIg = immunoglobulin-
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Targets and Therapies
Therapeutic options for AMR1,2,7 include:

Inhibition or depletion of B-cell function with
rituximab or corticosteroids

Interference with antibody function using
plasmapheresis, immunoadsorption, and/or
intravenous immunoglobulin (IVIg)

Interruption of plasma-cell function with bortezomib

Prevention of complement cascade using eculizumab
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The Population and the Risks

Over 96,000 patients currently are registered on the
waiting list for kidney transplantation.
» Almost 16% are prior organ-transplant recipients.
» Approximately 30% are sensitized to human leukocyte
antigen (HLA).8
» Highly sensitized patients with > 80% panel-reactive
antibody (PRA) wait three times longer to undergo
transplant surgery than do unsensitized renal transplant
recipients and have an average wait time of almost 10
years.9

Desensitized patients continue to have an increased
incidence of type I AMR and graft loss.10
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Pathophysiology in Sensitized Patients

Type I AMR in desensitized patients apparently
involves residual plasma cells and long-lived
allospecific memory B cells.11

Approximately one fourth of desensitized recipients
experience early AMR, usually within the first week
after transplant.12

Two thirds of these patients respond to
plasmapheresis.

The remainder may experience severe oliguric,
plasmapheresis-resistant rejection, which often is
accompanied by graft loss.
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Pathophysiology in Sensitized Patients
The principal effector mechanism of antibody-mediated
injury involves activation of the classic complement
pathway by the antigen-antibody complex deposition.13
Ig = immunoglobulin; HLA = human leukocyte antigen; DAF = decay-accelerating factor; Y-CVF = Yunnan-cobra venom factor
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Treatment of AMR: Plasmapheresis

Montgomery et al14 used plasmapheresis with IVIg to
reduce DSA strength before transplantation.

Induction with antithymoglobulin and steroids with
maintenance immunosuppression (tacrolimus and
mycophenolate mofetil) prevented AMR in most
desensitized patients.
» One third received anti-CD20 immediately before
transplant.
» Desensitization improved patient survival to 90% and 80%
at 1 and 5 years, respectively, as compared with 93% and
65% among those waiting for compatible donors.
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10
Treatment of AMR: Plasmapheresis

Montgomery and colleagues12 reported a 22%
incidence of early AMR that mostly responds to
further treatment with plasmapheresis and IVIg.

Approximately 50% of treated patients lose grafts
within 2 years.

Addition of complement inhibitor to splenectomy
has increased the rescue rate and significantly
reduced the development of tubular
glomerulopathy.12
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11
Phenotypes and Outcomes

Plasmapheresis better eliminates type I antibody
generated to major histocompatibility complex
(MHC) class I than it eradicates MHC class II
antigen.

Other phenotypes associated with poor outcome
include C4d-positive staining with glomerulitis,
peritubular capillaritis, and microcirculatory
inflammation.
» These differ from results seen in the setting of type II AMR.
» Further studies must incorporate immunologic and
histopathologic parameters into treatment algorithms that
balance risk with degree of therapeutic aggression.
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12
Complement Inhibition

Stegall and others15 compared 26 patients
desensitized to levels of low-to-moderate antibody
strength given eculizumab post transplant with 51
matched controls.

Within the first 3 months after transplant, AMR
occurred in 7.7% of patients given eculizumab and
41% of matched controls.

Protocol-required biopsies examined up to 1 year
after treatment showed no evidence of transplant
glomerulopathy.
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13
Risk of Rejection and DSA Titer and Type

DSAs are most commonly directed against HLA class
I (on all nucleated cells) or class II (on antigenpresenting cells and endothelial cells).
» DSAs may develop against non-HLA antigens, including
MHC class I–related chain A and B (MICA, MICB),
molecules of the renin-angiotensin pathway, and plateletspecific antigens2

DSA level, expressed as mean fluorescent intensity
(MFI), is proportional to the risk of rejection.
» Complement inhibition did not alter the DSA level but
reduced AMR in patients with a high DSA concentration
(control group, 100%; study group, 15%).15
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14
Eculizumab-Resistant AMR

Treatment of late AMR with findings suggesting
acute cellular rejection and AMR may involve
thymoglobulin, plasma exchange, and eculizumab.

Chronic AMR accompanied by negative C4d staining
may be a form of complement-independent rejection
and eculizumab-resistant rejection.

The best treatment of chronic AMR appears to be a
combination of therapeutic approaches, such as
combining bortezomib therapy with plasma
exchange and IVIg.16
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15
C4d-Negative AMR

Traditionally, detection of C4d has been required for
AMR diagnosis. However:
» Many C4d-negative cases have clinical and histologic
findings similar to those of rejection and exhibit DSAs.
» A substantial fraction of cases of chronic graft failure
previously labeled as calcineurin-inhibitor nephrotoxicity
may result from C4d-negative AMR.4

Sis et al17 examined 329 biopsy samples from
patients with graft dysfunction.
» Peritubular capillaritis and glomerulitis often were not
associated with DSA (27%) during year 1 post transplant.
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16
Molecular Scoring

Predictive molecular scoring systems based upon
levels of gene expression increasingly are being used
to augment standard diagnostic histopathology,
which fails to improve risk stratification.

The Banff Working Group5 is addressing a number of
approaches related to deficiencies, including:
» IgG subtyping
» MFI levels of DSA
» C1q-fixing DSA
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Molecular Scoring

Sellarés et al18 used Affymetrix microarray
technology to identify type II AMR in study biopsies
obtained 1 year post-transplant.

For many patients, biopsy results were related to
medication nonadherence.4

Survival was linked to timing of the biopsy and the
disease process identified.

The risk of graft loss was greatest during the initial
3 years following indication biopsy.
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18
Genetic Predisposition

A cohort of 30 human genes strongly associated with
AMR have been identified and validated.18

The genes include cadherin 13 (CDH13), chemokine
(C-X-C motif) ligands 10 and 11 (CXCL10 and
CXCL11), and fibroblast growth factor binding
protein 2 (FGFBP2), all of which are associated with
endothelial injury and cellular trafficking.

This molecular fingerprint, applied to all samples,
may be used to discriminate between AMR and other
causes of acute deterioration in graft function.18
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19
Subclinical AMR
Subclinical AMR is defined as graft changes that meet
established pathologic and serologic criteria for AMR
without graft dysfunction or concurrent ACR:

Serum creatinine level remains unchanged.

DSAs have low MFI values in the absence of
proteinuria.

Patients repeatedly undergo biopsy without
exhibiting clear evidence of rejection before
developing clinical and pathologic changes.

Quiescent disease may erupt later as a result of an
immunologic trigger.
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20
Subclinical AMR

Risk of graft loss is 77% higher among patients with
DSAs.

Some DSAs are more likely than others to result in
graft rejection.

Non-HLA and non-complement fixing antibody may
be responsible for subclinical AMR.
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21
Accommodation vs Subclinical Rejection

Accommodation is defined as the presence of
inhibitory mechanisms to the distal complement
cascade downstream of C4d cleavage.

Accommodation is often is seen in protocol-required
biopsies after ABO-incompatible transplantation.

Aside from ABO incompatibility, desensitized
patients with C4d-positive staining typically
experience tissue injury.

There is no way to differentiate C4d-positive biopsies
that represent accommodation from subclinical
AMR-mediated rejection.19
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22
C4d-Negative AMR

Approximately 10% of biopsies with features of acute
AMR are C4d negative.

Rejection may occur through complementindependent mechanisms.

Sis et al20 used microarray analysis to demonstrate
increased endothelial cell gene expression in biopsies
having histopathologic findings of AMR and DSA but
negative C4d staining.

This approach may represent a novel method of
AMR detection.
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23
Management of Subclinical AMR

Not all DSAs appear to pose the same risk.

Molecular phenotyping and electron microscopy may
help in detecting and managing subclinical AMR.

Gloor et al21 reported that treating desensitized renal
transplant recipients with subclinical AMR using
corticosteroids, plasmapheresis, and IVIg resolved
the histologic abnormalities; however, the long-term
clinical outcome of this strategy is unclear.
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Summary

Better understanding of acute AMR is the foundation
for successful treatment of desensitized patients by
blocking multiple points of the pathway.

Chronic AMR is a major cause of late graft loss and
remains less understood than acute AMR.

New gene-based molecular approaches to the
diagnosis of AMR offer hope of more timely and
effective treatment.
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References
1.
Levine MH, Abt PL. Treatment options and strategies for antibody mediated rejection after renal
transplantation. Semin Immunol. 2012;24:136–142.
2.
Puttarajappa C, Shapiro R, Tan HP. Antibody-mediated rejection in kidney transplantation: a review. J
Transplant. 2012;2012:193724.
3.
Lucas JG, Co JP, Nwaogwugwu UT, Dosani I, Sureshkumar KK. Antibody-mediated rejection in kidney
transplantation: an update. Expert Opin Pharmacother. 2011;12:579–592.
4.
Sellarés J, de Freitas DG, Mengel M, et al. Understanding the causes of kidney transplant failure: the
dominant role of antibody-mediated rejection and nonadherence. Am J Transplant. 2012;12:388–399.
5.
Mengel M, Sis B, Haas M, et al. Banff 2011 meeting report: new concepts in antibody-mediated rejection.
Am J Transplant. 2012;12:563–570.
6.
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7.
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experimental rationale. Transplant Int. 2012;25:623–632.
8.
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Accessed July 5, 2013.
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recipients. Clin Transplant. 2010;24:E247–E252.
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References
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Opin Organ Transplant. 2012;17:386–392.
13. Stegall MD, Chedid MF, Cornell LD. The role of complement in antibody-mediated rejection in kidney
transplantation. Nat Rev Nephrol. 2012;8:670–678.
14. Montgomery RA, Lonze BE, King KE, et al. Desensitization in HLA-incompatible kidney recipients and
survival. N Engl J Med. 2011;365:318–326.
15. Stegall MD, Diwan T, Raghavaiah S, et al. Terminal complement inhibition decreases antibody-mediated
rejection in sensitized renal transplant recipients. Am J Transplant. 2011;11:2405–2413.
16. Trivedi HL, Terasaki PI, Feroz A, et al. Abrogation of anti-HLA antibodies via proteasome inhibition.
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inflammation in kidney transplants. Am J Transplant. 2012;12:1168–1179.
18. Sellarés J, Reeve J, Loupy A, et al. Molecular diagnosis of antibody-mediated rejection in human kidney
transplants. Am J Transplant. 2013;13:971–983.
19. Park WD, Grande JP, Ninova D, et al. Accommodation in ABO-incompatible kidney allografts, a novel
mechanism of self-protection against antibody-mediated injury. Am J Transplant. 2003;3:952–960.
20. Sis B, Jhangri GS, Bunnag S, Allanach K, Kaplan B, Halloran PF. Endothelial gene expression in kidney
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Transplant. 2009;9:2312–2323.
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