how to diagnose and treat abmr

1. ABMR
• Introduction
• Definition
• Diagnosis /Classification (Banff Classification)
• Novel Biomarker
• Treatment of ABMR
• Emerging Treatment

4. • Antibodies directed against ABO blood group-
Iso agglutinins - IgM
Autoantibody – IgM/IgG
Alloantibody – IgG
• Antibody formation by ABO antigen(Carbohydrate) is T cell independent. so
there is no memory B or T cell.
• Rh antigen not present in tissue except RBC so it does not cause ABMR after
Transplant
• A,B,H antigen have two forms, one is tissue bind and other is soluble form which
is secreted by cells.
• 80% have both secreter and tissue bind form and 20% have only tissue bind form
• Soluble form of A,B,H system is responsible for AMR after Transplant.

5. There are two main classes of HLA antigens:
• Class I (HLA-A, HLA-B, and HLA-Cw)
• Class II (HLA-DR, HLA-DQ, and HLA-DP)
• Every person inherits each of the following antigens from each parent:
• HLA-A antigen
• HLA-B antigen
• HLA-C antigen
• HLA-DR antigen
• HLA-DQ antigen and
• HLA-DP antigen

9. HLA Nomenclature

10. HLA Epitopes
• It is site on antigen where antibody(paratope) binds.
• It is conformational amino acid arrangements.
• Epitopes on a single HLA – Private epitope.
• Epitopes shared by multiple antigen – Public epitope.
• Since 2006 to 2017 multiple epitopes are identified by serological method.
• HLA Class 1- 194 epitope(including 56 cryptic epitope)
• HLA Class 2-
 DRB1-60
 DQB1-15
 DQA1-3
 DPB1-5
• The defining amino acids had to be with in the antibody binding span, estimated at 494-750 A2
area(diameter 15 A) and amino acid must be exposed at the surface of antigen.

12. Humoral response to antigen

13. 1. T cell dependent-most protein antigen
2. T cell Independent-most polysaccharide and lipid antigen

14. T cell dependent-most protein antigen
B cell ingest soluble protein antigen → degradation of antigen→
peptide of antigen bounds to class 2 MHC to recognize T helper cell →
T Helper cell activated
↓
Express CD 40 L and secrete several cytokine
↓
B cell interact with T cell by CD 40, receptor and cytokines secreted by
TH cell ↓
B cell activated

16. • Plasma cell derived from activated B cell.
• These plasma cell secrete antibody that recognize the same antigen
that was bound to BCR
2. T cell Independent-most polysaccharide and lipid antigen
• Non protein antigen directly stimulate B cell
• T cell independent humoral activation do not have Immunoglobulin
class switching, affinity maturation and B cell memory

19. HLA antibody
• DSA- Anti HLA antibody present in recipient which are against the
Mismatch antigen.
• Non DSA – Anti HLA antibody which are other than Mismatch
antigen. presence of this antibody is determined by PRA(Panel
reactive antibody)

21. Pathogenesis

24. Diagnosis

25. Gold standard – kidney Biopsy

26. The Banff 2019 Kidney Meeting Report
• Active ABMR
• Chronic active ABMR
• Chronic ABMR

27. The Banff 2019 Kidney Meeting Report

28. Microvascular inflamation

29. Features of active
antibody mediated
rejection
A: Acute tubular injury
B: microcirculation inflammation with
neutrophils and mononuclear cells in
glomeruli-glomerulitis
C: peritubular capillaries-peritubular
capillaritis
D: fibrinoid necrosis of artery

30. Intimal and Transmural arteritis

31. C4 d Staining
• A – IF Study in frozen section
• B - IHC study in paraffin block

32. The Banff 2019 Kidney Meeting Report

33. Chronic Active
ABMR
A. Double contour formation in glomerulus
with chronic glomerulitis in chronic active
antibody mediated rejection-Banff score cg3
and normal glomerulus.
B. Glomerulitis in chronic active antibody
mediated rejection (Banff score g3, cg3) with
diffuse double contour formation (glomerular
capillaries with double contours are filled
with swollen endothelial cells and
inflammatory cells, among them
macrophages predominate (CD68 and PAS).

34. Chronic active vascular rejection with intimal endarteritis and
intimal fibrosis

35. TMA
A:Acute vascular thrombotic
microangiopathy in active antibody mediated
rejection
B:Chronic glomerular and vascular
thrombotic microangiopathy in chronic active
antibody mediated rejection (Weigert stain)

37. Chronic
ABMR
A:Chronic burn out
vascular rejection
without intimal
infiltrate in arcuate
artery-Banff score cv3

38. Chronic ABMR
B: Intimal fibrosis due to chronic rejection is
superimposed on fibroelastic lamelation
associated with arterial hypertension.
C: Artery with elastic duplication due to
arterial hypertension without rejection.

39. Limitation of Renal Pathology
• Invasive
• Specificity
• Inter-and Intra-Observer variability
• Reproducibility

42. What is a biomarker?
The National Institutes of Health Biomarker Definition Working Group
provides the subsequent definition: A characteristic that is objectively
measured and evaluated as an indicator of normal biological
processes, pathogenic responses, or pharmacological responses to a
therapeutic intervention.

43. NOVEL BIOMARKER CLASSIFICATION
Immunological
Chemokines
Free micro ribonucleic acid
Leukocyte subclasses
Gene expression profiles
Donor-derived cell-free deoxyribonucleic acid
Non Immunological

44. a- P < 0.001 vs histology.
b-P < 0.05 vs non-rejection group.
c-P < 0.02 vs non-rejection group.
d-P <0.01 vs non-rejection group

45. a-P < 0.001 for TCMR vs controls.
b-P < 0.001 for UTI vs controls.
c-P < 0.005 vs histology.
d-P <0.001 vs controls

46. A-P < 0.001 vs controls.
B-P < 0.001 vs TCMR.
C-P < 0.0001 vs biopsies w/o mvi.
D-P < 0.05 vs controls

47. aP < 0.001 vs controls.

48. A-P < 0.005 vs low level dd-cfDNA pts.
B-P < 0.0001 vs low level dd-cfDNA pts.
C-P < 0.001 vs no rejection.

50. • Dd cf DNA discriminates Active rejection(acute/active ABMR;
Chronic active ABMR or TCMR) from no active rejection with high
accuracy.
• It is more accurate than serum creatinine in diagnosis of active
rejection.
• It is highly sensitive in distinguishing ABMR from non ABMR related
renal dysfunction.
• Levels decreses following successful rejection treatment.
Roy D. Bloom et al. Cell-Free DNA and Active Rejection in Kidney Allografts . J Am Soc Nephrol 28: 2221–
2232, 2017. doi: https://doi.org/10.1681/ASN.2016091034

52. CLINICAL PHENOTYPES OF AMR
• Early Posttransplant(<30 Days) active AMR
• Late (>30 Days) Posttransplant AMR With Preexisting DSA
• Late (>30 Days) AMR Associated With dn DSA

53. Early Posttransplant(<30 Days) active AMR
• In patients who have measurable DSA at the time of kidney transplant
or who have an immunologic amnestic response due to previous
exposure to allo-HLA, active AMR can occur within the first 30 days
posttransplant.
Risk of early posttransplant AMR
growing DSA strength or breadth at the time of transplant
the degree of flow cytometric crossmatch positivity
number or breadth of cross-reactive DSA specificities.
• This form of AMR is uncommon

54. • Early posttransplant AMR occurs in up to 40% of patients with
preformed DSA and a positive flow cytometric crossmatch.
• This aggressive form of active AMR typically presents with an abrupt
increase in DSA accompanied by allograft dysfunction
• From a histological perspective, the criteria for Banff active AMR are
met and C4d is usually positive.
• With prompt diagnosis and treatment, patients can recover allograft
function and histological features of active AMR frequently resolve
completely.

55. Late (>30 Days) Posttransplant AMR With
Preexisting DSA
• many patients with preexisting DSA do not develop an aggressive
early AMR
• they can develop an indolent and progressive form of AMR that is
usually initially detected on a surveillance biopsy (in the setting of
stable function) or on a for-cause biopsy for mild allograft
dysfunction.
• Histological findings are dependent on the timing of the biopsy
• When detected early, MVI in glomeruli and peritubular capillaries is
the predominant finding and C4d staining may or may not be present.

56. • MVI tends to persist and is later accompanied by chronic histological
features including transplant glomerulopathy and peritubular basement
membrane multilayering.
• there is often minimal if any reduction in glomerular filtration rate
(GFR) or proteinuria even when mild chronic features are present.
• Overtime, however, the GFR declines and the patient becomes
proteinuric with graft failure often occurring several years after
transplant.

57. Late (>30 Days) AMR Associated With dn DSA
• In the current era the most common form of AMR is associated with
dn DSA.
• Dn DSA is a new DSA detected after >3 months posttransplant in the
context of inadequate immunosuppression.
• This form of AMR often presents with allograft dysfunction and
concomitant or preexisting TCMR.
• In patients who have routine surveillance DSA testing or surveillance
biopsies, the presentation can be more indolent and is similar to that of
late posttransplant AMR in patients with preexisting DSA (subclinical
AMR associated with dnDSA)

58. • AMR with dnDSA is associated with inferior allograft survival when
compared with AMR from preexisting DSA after adjusting for clinical,
histological, and immunologic characteristics.
• Allograft survival was 63% in patients with preexisting DSA and only 34%
in patients with dnDSA 8 years after the rejection diagnosis.
Aubert O, Loupy A, Hidalgo L, et al. Antibody-mediated rejection due to preexisting versus de novo donor-specific antibodies in
kidney allograft recipients. J Am Soc Nephrol. 2017;28:1912–1923.
Haas M, Mirocha J, Reinsmoen NL, et al. Differences in pathologic features and graft outcomes in antibody-mediated rejection of renal allografts due to
persistent/recurrent versus de novo donor-specific antibodies. Kidney Int. 2017;91:729–737. Haas M, Mirocha J, Reinsmoen NL, et al. Differences in
pathologic features and graft outcomes in antibody-mediated rejection of renal allografts due to persistent/recurrent versus de novo donor-specific
antibodies. Kidney Int. 2017;91:729–737.
• Compared with patients with preexisting DSA, those with dnDSA tend to
have increased proteinuria and increased expression of interferon-γ–
inducible, natural killer cell, and T-cell transcripts at presentation.

59. CONSENSUS FOR MEASURING AND
MONITORING OF DSA
• Initial Assessment for Anti-HLA DSA
• Monitoring for De Novo DSA
• Interpreting Positive DSA Results
• Additional DSA Testing for Risk Stratification

60. Initial Assessment for Anti-HLA DSA
donor and recipient HLA typing(includes A; B; C; DRB1; DRB3, 4, 5;
DQA1/DQB1; and DPA1/DPB1)
anti-HLA antibody screening
history of allosensitizing events
• For anti-HLA–sensitized recipients, a high-resolution level of typing,
reaching the allelic level (ie, the so-called “4-digit” typing), should be
undertaken to match the resolution of the alloantibody identification
assays.

61. Monitoring for De Novo DSA
• Monitoring for dn DSA is recommended in the following settings:
 immunosuppression reduction by physician for any reason
 known patient medication nonadherence.
 at the time of rejection episode (T cell or antibody mediated) .
• The presence of dn DSA is a general indicator of under-
immunosuppression and signals the need to reevaluate maintenance
immunosuppression.

62. Interpreting Positive DSA Results
• The SAB test detecting DSA has been an important advancement to
the field; however, the test has limitations that must be identified for
correct interpretation.
• First, the SAB test has a high coefficient of variation, and thus, the
positive cutoff varies among and within laboratories.
• SAB tests are also prone to interference from external substances,
bead saturation, and “shared-epitope” phenomenon, which can lead to
a falsely low MFI.

63. Additional DSA Testing for Risk
Stratification
• The risks of AMR from highest to lowest based on crossmatch and
SAB-positive testing are the following:
 positive complement-dependent cytotoxicity (CDC) crossmatch.
 positive flow cytometric crossmatch.
 negative crossmatch.
 Testing to assess the complement binding ability of DSA (C1q or C3d)
is commercially available, but do not recommend routine use of
complement binding assays unless it is used as a means of predicting
high strength DSA.

64. AVAILABLE EVIDENCE FOR THE
TREATMENT OF ACTIVE AND CHRONIC
ACTIVE AMR
Most reports on the treatment of AMR are small and include
heterogeneous patient populations.
These studies frequently include mixed antibody and TCMRs
do not differentiate responses based on the timing of AMR detection
make no distinction between dn DSA and preformed DSA
• The heterogeneity of available studies makes it difficult to draw
meaningful conclusions about treatment effects.
• As a consequence, treatment studies for AMR are rarely comparable,
and the available evidence is generally of low quality

65. Desensitization(ABO incompatible)

66. Desensitization protocol(ABO INCOMPATIBLE)

68. Available Strategies for DSA removal
1.Removal of Antibodies by Plasma phereis or Immunoadsorption
PP is not specific for Ig removal
Anti-HLA antibody titer rebounds
2.Inhibition of Antibody production
 Rituximab (Anti-CD20):
• Pre-B and mature B lymphocytes
• Plasma cell do not express CD20
 Bortezomib (proteasome inhibitor): • Induce apoptosis of plasma
cells

69. 3.Intravenous Ig:
– Neutralization of circulating anti-HLA antibodies through anti-
idiotypic antibodies.
– Bind C3b and C4b and neutralize C3a and C5a – binding to Fc
receptors
4.Splenectomy:
– Major source of Lymphocyte including B cells and plasma cells

70. AVAILABLE EVIDENCE FOR THE
TREATMENT OF ACTIVE AND CHRONIC
ACTIVE AMR
• Plasma Exchange and IVIG
• Complement Inhibitors
• Rituximab
• Imlifidase
• Antithymocyte Globulin
• Splenectomy
• Proteasome Inhibitor: Bortezomib
• Cyclophosphamide
• Interleukin-6 Inhibitors

73. CONSENSUS FOR TREATMENT OF EARLY
ACTIVE AMR (≤30 DAYS POSTTRANSPLANT)
• The current evidence for treatment options in active AMR is of limited
quality
• 2019 consensus view was that the combination of PLEX, IVIG with
corticosteroids could be regarded as standard of care, consistent with the
conclusions of the FDA workshop and KDIGO guidelines.
• in some centers, the use of corticosteroids is reserved for patients with
concomitant TCMR.
• adjunctive therapy with other agents has been used in specific settings
especially when the risk of graft loss is considered high.
• The recommended adjunctive therapies include complement inhibitors,
rituximab, or splenectomy depending on availability.
• Where concomitant TCMR is present, it should be treated.

82. Emerging Therapy

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