Prognostic significance of C4-positive vs. negative rejection Prognostic significance of C4-positive vs. negative rejection

Heinz RegeleHeinz RegeleDepartment of PathologyDepartment of Pathology

Innsbruck Medical UniversityInnsbruck Medical University

Heinz RegeleHeinz RegeleDepartment of PathologyDepartment of Pathology

Innsbruck Medical UniversityInnsbruck Medical University

C4d-negative rejectionC4d-negative rejection

Issues to discuss

Clinical relevance (prognosis, diagnostic features)

Biology

Has all clinical and morphological features of antibody mediated rejection but lacks C4d in transplant biopsies

C1C1

Allograft Endothelial cells

MechanismsMechanisms ofof HumoralHumoral AllograftAllograft RejectionRejection

MACMAC

PMNPMN

MøMøT-cellT-cell MøMø NK-cellNK-cell

C3bC3b

C4dC4d

C4d

Dual Role of ComplementDual Role of Complement

Biology C3, C5, C5b-9

Diagnostic marker C4d (C3?)

Banff Banff classification of renal allograftclassification of renal allograft rejection rejection

C4d Capillaritis Arterial necrosisATN

+ or or+

DSA

MHC I

anti-C4d

MHC II

Renal C4d deposits in 93 patients with early allograft dysfunction

0102030405060708090

100

0 41 32 5 96 87 10 1211

C4d- (N=42)

Total (N=93)

C4d (+) (N=8)

C4d+ (N=43)

90%

72%

63%

57%

Months post TX

% A

llog

raft

su

viva

l

Capillary C4d deposition and allograft survivalCapillary C4d deposition and allograft survival

Feucht et al, Kidney Int, 43:1333, 1993

C4d posN = 16

C4d neg/FCXM posN = 22

C4d neg/FCXM negN = 20

C4d staining and FCXM (Flow-Cytometry X-Match) of corresponding seraC4d staining and FCXM (Flow-Cytometry X-Match) of corresponding sera 113 biopsies of 58 renal allograft recipients113 biopsies of 58 renal allograft recipients

In 2 Patients severe rejection reversible by IA 4 allografts lost

1 allograft lost

G.A. Böhmig et al, JASN 2002

Tissue injury and outcome in DSA positive patientsTissue injury and outcome in DSA positive patients

A. Loupy et al., AJT 2011

Microvascular injury and chronic ABMRMicrovascular injury and chronic ABMR

A. Loupy et al., AJT 2011

….C4d may not be a sufficiently sensitive indicator of activity, MI and DSA being more robust predictors of bad outcome.....

C4d-negative DSA-associated microvascular injuryC4d-negative DSA-associated microvascular injury

•Sampling error?

•Antibody-mediated but complement-independent injury?

•Inadequate sensitivity of C4d detection?

•Remnants of previously active ABMR?

Recipients withoutadaptive immune system(RAG1 KO)

MHC incompatible donor Anti-donor-MHC moAb

Experimental evidence for C4d negative ABMRExperimental evidence for C4d negative ABMR

Jindra PT, Transplantation 2006

Non complement fixing anti donor IgG cause chronic transplant arteriopathy (CTA). CTA even developed in RAG1-/-C3-/- double KO mice upon injection of DSA, strongly suggesting a complement independent mechanism of injury

T. Hirohasi, AJT 2010

NK cells are essential for the development of DSA induced CTA in a FcRIII dependent mechanism (in absence and presence of complement). DSA alone or in conjunction with macrophages only do not generate CTA.

T. Hirohasi, AJT 2012

Current Opinion in Organ Transplantation 2010; 15: 42-48

Expression of endothelial cell associated transcripts (ENDATs) is present in all types of rejection but significantly higher in ABMR.

Only 13/50 (26%) of kidneys with high ENDATs and DSA were C4d positive

Only 38% of kidneys with high ENDATs and DSA that subsequently developed chronic ABMR were C4d positive

Reduced graft survival in C4d-negative ABMR Reduced graft survival in C4d-negative ABMR

B. Sis et al., AJT 2009A: DSA E: ENDAT C: C4d

C4d negative ABMR – the clinical approachC4d negative ABMR – the clinical approach

What is the prevalence of DSA in C4d negative (micro)vascular injury in the general population (of TX-recipients)?

What is the clinical course of C4d negative rejection without specific treatment?

Which diagnostic features are associated with progression to chronic AMR and/or graft loss?

Gaston, Transplantation 2010; Loupy AJT 2009

Alloantibodies are present inAlloantibodies are present in

38-70%38-70%

of C4d negative glomerulitis casesof C4d negative glomerulitis cases

Prevalence of alloantibodiesPrevalence of alloantibodies in C4d-negative microvascular injuryin C4d-negative microvascular injury

Issa, Transplantation 2008; Sis, AJT 2007; Shimizu Clin Transpl 2009, Haas AJT 2011

and inand in

42-100%42-100%

of C4d negative glomerulopathy casesof C4d negative glomerulopathy cases

Biopsies for cause (n=481)

C4d neg + mv lesions+ serum(n=28)

C4d pos (n=75)C4d neg (n=378)

Renal TX12/00 – 2/05 (n=691)

C4d negative ABMR – the clinical approachC4d negative ABMR – the clinical approach

Regele et al, manuscript in preparation

DSA in C4d-negative vascular injuryDSA in C4d-negative vascular injury

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Neg Cont C4d-pos ContC4d-neg mvi Neg Cont C4d-pos ContC4d-neg mvi

P=0.1 P=0.7 P=0.09 P=0.17

Anti-HLA antibodies Donor specific antibodies

Regele et al, manuscript in preparation

Graft survival in C4d-negative vascular injuryGraft survival in C4d-negative vascular injury

Death censored graft survival

876543210

1.0

0.8

0.6

0.4

0.2

0.0

P<0.0001 (C4d+ vs C4d-)

C4d+ (n=76)

C4d- (n=378)

C4d- mvi (n=28)

Regele et al, manuscript in preparation

Summary C4d-negative ABMRSummary C4d-negative ABMR

Clinical observations and experimental evidence strongly support the concept of C4d-negative ABMR

C4d-negative rejection tends to show a rather slow and indolent course

Complement independent mechanisms seems to play a much more important role in chronic ABMR than in acute ABMR

Reliable diagnostic features of C4d-negative ABMR for therpeutic decisions in individual patients still need to be established

(Micro)vascular injury is a key diagnostic feature that should raise the suspicion and trigger the search for further evidence of ABMR