Acute cellular and humoral
rejection
Eva Honsova
Institute for Clinical and Experimental Medicine
Prague, Czech Republic
eva.honsova@ikem.cz
Graft rejection:
The new era of transplantation began during World War II.
1. Cellular theory (Peter Medawar): the process of graft rejection is
immunologically dependent. The cells (easy to see on histological
slides) were recognized and identified as a cause of tissue damage.
Hyperacute rejection (HR)
thrombosis
• The antibodies are not seen in
routine histological staining.
• HR can occur immediately after
transplantation
• HR was observed when the
kidney was transplanted into a
recipient with pre-existing DSA
• HR can also be caused by
antibodies directed at allogenic
blood groups A and B
• New generation of laboratory
tests prevents HR
Graft rejection:
• 2. Humoral theory (Paul Terasaki): evidence that also in
later periods after transplantation antibodies must
participate in graft damage.
2000: 80/70% at 5 years
They were unable to prove this theory: no tissue marker of confirmation. Several
landmark observations enabled the definition of dg. criteria of A-MR: P. Halloran: AR
with „de novo“ DSAs production and poor prognosis.
H. Feucht: studied complement components and recognized the relationship of C4d
deposition in PTCs in kidney grafts to graft dysfunction.
Complement system
C4d
Positive C4d staining is a marker of antibody-mediated rejection and represents
something like an imprint that the reaction occurred at the place of positive
staining.
Detection of C4d (positive staining in PTCs)
immunofluorescence
immunoperoxidase
Classification of rejection changes
• various centers were developing
their own protocols and their own definitions of
the morphological features
• without standardization of the nomenclature
the communication among various centers
would remain unsatisfactory
• Banff classification since 1991
• The schema underwent considerable evolution,
and was repeatedly revised and modified in
follow-up meetings during a 2-year period
Kidney graft biopsy, adequacy criteria
• A large number of conditions can affect the allograft, frequently in
combination with varying degrees of arteriosclerosis.
• the pre-biopsy clinical diagnosis differed from the definitive
diagnosis in 42% of episodes of graft dysfunction (Pascual et al.
Transplantation 1999;67:737-41)
• Therapy is changed in 60% following graft biopsy
a) adequacy of the sample; b) processing of the tissue
LM
2 cores 10 gli
2 arteries
3 H&E
3 PAS
1-3 Trichrom or Sirius red with
elastin
IF
EM
3 gli
1glus
IgG, IgA, IgM
C3, C4d
Fb, κ,λ light chains, (HLA-DR
or others)
PU,
hematuria,
1 year after Tx
The immunologic threat to the graft begins
before transplantation
A. Systemic effects of ischemia/reperfusion injury
I/R up-regulates the expression of HLA antigens by the
graft, the release of a cascade of chemokines,
proinflammatory cytokines, and adhesion molecules.
The increased display of HLA antigens intensifies the immune
response.
B. Each graft has its “medical history“; varying degrees of
preexisting, clinically silent injury, mainly vascular
nephrosclerosis
No collateral vessel among arteries and arterioles; stenosis
of the lumen represents chronic ischemia in the interstitial
tissue.
Acute T-cell-mediated rejection
C: 3. Borderline Changes:"Suspicious" for acute T-cell-mediated r.
C: 4. Acute T-cell-mediated rejection (type/grade)
• IA. Cases with significant interstitial infiltration (>25% of
parenchyma affected, i2 or i3) and foci of moderate tubulitis (t2)
• IB. Cases with significant interstitial infiltration (> 25% of
parenchyma affected, i2 or i3) and foci of severe tubulitis (t3)
• IIA. Cases with mild to moderate intimal arteritis (v1, <25% of the
luminal area)
• IIB. Cases with severe intimal arteritis comprising > 25% of the
luminal area (v2)
• III. Cases with "transmural" arteritis and/or fibrinoid change and necrosis of
medial smooth muscle cells with accompanying lymphocytic inflammation (v3)
Acute T-cell-mediated rejection, tubulitis-schema
Significant lowering of the rate of episodes of ACR to approximately 5-10% in the 1st year
Grade I: 65-70%, grade II: 30%
Huge progress was made in our understanding of immunological mechanisms of rejection
CD8 recognize
peptide antigens
presented by class I
MHC, produce IFNγ
Mediate direct
cytotoxicity via
granzymes and
perforin
CD4 recognize peptide antigens
presented by class II, can be
divided according to their
cytokine production:
Th1: IFNγ , IL2, TNFα, typically in
infiltrate of acute rejecting grafts
TH2: IL4,IL5,IL10, provide help
for B cells and production IgE –
promote eosinophils
Inflammatory cytokines
produced by T cells activate
epithelial cells, which in turn
attract more T cells.
Acute T-cell-mediated rejection, type I
tubulitis in non-atrophic tubules
Banff criteria:
•
IA. i:>25% of parenchyma affected, i2 or i3 and t2
•
IB. i> 25% of parenchyma affected, i2 or i3 and t3
Chapel Hill Standards
1. i ≥5%
2. Mild to moderate interstitial edema
3. Tubulitis (t1 in ≥3 tubules in most inflamed area),
- scattered eosinophils and ATI are common
- MHC class II in tubular cells
- If criteria 1-3 are not fulfilled, but tubules strongly
expressed MHC class II, then an episode of ACR is suggested
tubulitis
Acute T-cell-mediated rejection, type I
dg. problems and differential diagnosis
• How much inflammation is
reactive in subcapsular
space early posttransplant
• Resolving/partially treated
rejection
• inflammation in areas of
interstitial fibrosis with t1 in
the interface areas
• 20-65% ATMR show C4d
deposits along PTCs: mixed
cellular- and antibodymediated rejection
Differential diagnosis
• Drug-induced TIN
Difficult or impossible to
distinguish from ATMR
• Pyelonephritis
neutrophlic casts
• Polyomavirus nephropathy
plasma cells, IH detection
Acute T-cell-mediated rejection, type I
Dif. Dg.: polyoma virus nephropathy
Acute T-cell-mediated rejection, type II and III
arteritis or endotheliitis
Acute T-cell-mediated rejection, type II and III
differential diagnosis
AS, hypertension
Atheromatous
embolism
Severe hypertension
If we strictly follow the Banff criteria, one lymphocyte is
enough for the dg. type II ATMR rejection.
Pre-existing donor disease
Acute B-cell-mediated rejection/humoral
rejection
• Recognition of AMR requires demonstration of C4d
and circulating antibodies.
The diagnostic criteria of AMR
(cases that meet 2 criteria are considered suspicious for
AHR)
1. Neutrophil/lymphocyte margination (capillaritis),
and/or thombosis/necrosis
2. C4d+ in PTCs
3. Circulating anti-donor antibodies (DSA)
Categories:
1.Hyperacute rejection
2. Acute B-cell-mediated rejection, late acute B-cell-mediated
3. Accommodation
Hyperacute rejection (HR)
• Now, HR is not included
in Banff schema
• Complement dependent
• recipient with preexisting DSA
• Can be C4d negative
Differential dg.:
• Vascular thrombosis
(artery or vein), technical
problems or
hypercoagulable state
• Donor TMA
Acute B-cell-mediated rejection/humoral
rejection
C4d is the terminal inactive split product of antibody-activated
classical complement cascade and positive C4d staining represents
something like an imprint of the reaction driven by antibodies.
Scoring of C4d staining
• C4d0 negative
0% of ptcs
• C4d1 minimal C4d detection 1-10%
• C4d2 focal C4d positive
11-50%
• C4d3 diffuse C4d positive
>50%
Acute B-cell-mediated rejection
capillaritis: gli, PTCs; thrombosis
AHR has occurred with all IS regiments. The pathology of AHR has a wide spectrum of
findings. However, none of these features is specific.
Acute B-cell-mediated rejection
Anti-donor Abs such as those directed at
MHC antigens can trigger AMR.
However, the absence of DSA cannot be
taken to exclude AMR.
Cases with: C4d+, DSA+
Cases with: C4d+, DSA• some antigens may be expressed on
the endothelial cells and not on
lymphocytes, which are typically used
for the test (MICA).
• graft can absorb huge amounts of
antibodies from blood and Abs can be
Sis B; Halloran P.
below the level of detection.
Endothelial transcripts uncover a previously
unknown phenotype: C4d-negative
Cases with: C4d-,DSA+
antibody-mediated rejection.
• Negative staining may result from nonCurrent Opinion in Organ Transplantation. 15(1):42-48,
February 2010.
complement fixing antibodies, low
reactivity of Abs.
Acute B-cell-mediated rejection
cg
Phenomenon of so-called
accommodation was repeatedly
described in AB0 incompatible kidney
grafts.
In this situation, there are DSA, and C4d
positive staining in PTCs.
There is no tissue injury in the graft and
the function is stable.
However, in long-term studies, the
morphological features of chronic injury
were demonstrated more frequently
than in AB0 compatible recipients.
Rejection remains a central challenge in
the field of transplantation
Although huge progress has been made in our understanding
of immunological mechanisms of rejection there is still a
lot unknown.
???
• Is humoral response always pathogenic?
• What is the role of IgG subclasses in transplantation?
• Can some antibodies block these DS antibodies which bind
the complement?
• Are all DSA harmful?
• Is there acute antibody mediated rejection with arterial
injury similar to type II ATMR? (humoral v, in mice it is so)
(Hirohashi et al. Am J Transplant 2010:10;510-517)
Now we do not know what technique will represent a
breakthrough and a great improvement in diagnosis of
rejection; gene transcripts or perhaps microRNA, or something
unknown …
???