SLIDE 1
C3 glomerulopathy and monoclonal gammopathy: Role of monoclonal Ig - - PowerPoint PPT Presentation
C3 glomerulopathy and monoclonal gammopathy: Role of monoclonal Ig - - PowerPoint PPT Presentation
C3 glomerulopathy and monoclonal gammopathy: Role of monoclonal Ig on complement dysregulation 4th meeting of IKMG Dr Sophie Chauvet Department of Nephrology, European Hospital Georges Pompidou, APHP, Paris INSERM 1138, Research Team
SLIDE 2
SLIDE 3
Complement system
Alternative pathway
C3(H2O) Alternative C3 convertase C3bBb
hydrolysis Classical pathway
Immun Complexes
Lectin pathway
mannoses
C1q MBL C3 convertase C4bC2a C3a Opsonisation
C3b, iC3b C3a, C5a Activation and Lysis
C5 convertase
C6 C7 C8 C9
C5b
C5b9
Chemotaxis C3 C3b
SLIDE 4
Bb C3b C3b B B C3b
D Mg++
C3
Auto amplifica-on Hydrolyse spontanée
D C3 C3H2O C3H2O B B C3b
Complement alternative pathway is physiologically activated and amplified on activating surface
C3 conv C5 conv
B b C 3 b
MAC Activating surface
Spontaneous hydrolysis
C3a C5a
SLIDE 5
Bb C3b C3b B B C3b
D Mg++
C3
Auto amplifica-on Hydrolyse spontanée
D C3 C3H2O C3H2O B B C3b
FH FH, FI CD46, CR1
Complement alternative pathway regulation in fluid phase and on host cell surface
C3 convertase C5 convertase
Bb C3b
MAC FH
inhibition of C3convertase formation
FH
C3 convertase dissociation
Inactivating cleavage of C3b in iC3b (cofactor activity)
Non activating surface
SLIDE 6
Overactivation of the AP and kidney diseases
Atypical HUS
= acute Thrombotic Microangiopathy with acute renal failure
C3 glomerulopathy
Chronic kidney disease
F.Fakhouri et al, Lancet 2017 Smith et al, Nat Rev Nephrol 2019
Target of complement attack= endothelial cell Target of complement attack= mesangial cell
C3b
Bb
C3b
Bb
C5a C5a
<0.6/Millions/an <0.2/Million/an
Bb C3b Bb C3b
SLIDE 7
Complement abnormalities aHUS C3G
Genetic variant 60-70% 20% Loss of function of regulators (FH, FI, CD46) 75% 90% Gain of function of C3 convertase (C3, FB) 25% 10% Acquired abnormalities 10% 50-80% Gain of function of convertase (C3/C5 NeF, anti-C3b or anti-FB antibodies)
- 40-65%
Loss of function of FH (Anti-FH antibody) 10% 15%
↓ C3 level (30%) ↓C3 level (40-60%) ↑sC5b-9 (65%)
Frémeaux-Bacchi et al, CJASN 2013 Dragon Durey MA et al, Nat Rev Nephrol 2016 Marinozzi MC et al, KI 2017 Blanc et al. J Immunol 2016
Complement abnormalities are distinct in aHUS and C3G
SLIDE 8
MIg and C3G/aHUS occurence: Epidemiological data
Atypical HUS C3 glomerulopathy
146 TMA between 2000 and 2016 20 patients with MIg 21% of patients aged over 50
Ravindran et al. Kidney Int 2017
22 patients with MIg and aHUS 29% of patients with aHUS age over 50 36 patients with C3G associated with MIg: 65% of patients aged over 50
Ravindran et al. Kidney Int 2018
60 patients with C3G associated with MIg 65% of patients aged over 50
Chauvet et al. Blood 2017 Dr Frémeaux Bacchi, aHUS french registry, unpubished data
SLIDE 9
C3G and MIg-C3G have distinct complement profiles
Chauvet et al. Frontiers Immunol 2018
complement biomarkers are distinct Target of anti-complement Abs are distinct Variations in complement genes are less frequent
SLIDE 10
MIg=auto antibody? Target= C3bBb, C3b, FB, FH, FI, CR1….?
PIGNMID and monoclonal lambda LC with anti-FH antibody activity
(Jokiranta et al. J Immunol 1999)
Part 1: Working hypothesis
Bb C3b C3b B B C3b
D Mg++
C3
Auto amplifica-on Hydrolyse spontanée
D C3 C3H2O C3H2O B B C3b
SLIDE 11
pt MIg Anti complement protein Ab spécificity Heavy chain Light chain G40 IgAk Anti FI a k G38 IgG2k Anti FH g2 k G51 IgAk Anti FH a k G7 IgG1l Anti FH g3 k and l G22 IgG4k Anti FH g2 k and l G8 IgG4l Anti CR1 g1 k and l G13 IgG1k Anti CR1 g1 k and l G15 IgG1l Anti CR1 g1, g4 k and l G35 IgG3k Anti CR1 g1 k and l G46 IgG2k Anti CR1 g1 k and l G56 IgG1k Anti FI g2 k and l G20 IgG2l Anti FH/CR1 g1 anti FH and g1 anti FH k and l G32 IgG4l anti FH/anti CR1 g2 anti FH and g1 anti CR1 k and l
Comparision of HC and LC isotype specificy
SLIDE 12
pt MIg Anti complement protein Ab spécificity Heavy chain Light chain G40 IgAk Anti FI a k G38 IgG2k Anti FH g2 k G51 IgAk Anti FH a k G7 IgG1l Anti FH g3 k and l G22 IgG4k Anti FH g2 k and l G8 IgG4l Anti CR1 g1 k and l G13 IgG1k Anti CR1 g1 k and l G15 IgG1l Anti CR1 g1, g4 k and l G35 IgG3k Anti CR1 g1 k and l G46 IgG2k Anti CR1 g1 k and l G56 IgG1k Anti FI g2 k and l G20 IgG2l Anti FH/CR1 g1 anti FH and g1 anti FH k and l G32 IgG4l anti FH/anti CR1 g2 anti FH and g1 anti CR1 k and l
MIg acts as a anti complement protein Ab in 3/13 tested samples
SLIDE 13
pt MIg Anti complement protein Ab spécificity Heavy chain Light chain G40 IgAk Anti FI a k G38 IgG2k Anti FH g2 k G51 IgAk Anti FH a k G7 IgG1l Anti FH g3 k and l G22 IgG4k Anti FH g2 k and l G8 IgG4l Anti CR1 g1 k and l G13 IgG1k Anti CR1 g1 k and l G15 IgG1l Anti CR1 g1, g4 k and l G35 IgG3k Anti CR1 g1 k and l G46 IgG2k Anti CR1 g1 k and l G56 IgG1k Anti FI g2 k and l G20 IgG2l Anti FH/CR1 g1 anti FH and g1 anti FH k and l G32 IgG4l anti FH/anti CR1 g2 anti FH and g1 anti CR1 k and l
Isotype specificity of Abs and MIg are different in 75% of tested samples
SLIDE 14
Modification of complement protein binding sites on Ig that could enhance AP activation.
Bb C3b C3b B C3b
D
Part 2 Working hypothesis
C3b
Monoclonal Ig
Pecularities of MIg:
- Abnormalities of glycosilation
- mutation in VD and CD
- capacity to form macromolecular complexes
Cogné M et al. Blood 1992
SLIDE 15
50 25 12.5 0 50 25 12.5 0
α’ β α
IgG-HD G12
FB (ng)
Ig-HD MIg-C3GN MIg w/o KD C3NeF 0.0 0.5 1.0 1.5
α'/beta ratio *** ** NS NS ** m+2SD
Ig-HD MIg-C3GN MIg w/o KD 0.0 0.5 1.0 1.5
α'/beta ratio ** * NS m+2SD
45min (37°C)
Study of C3 cleavage in C3b (WB) 13/34 patients Ig « activators as platform » 12/33 patients Ig « activators in fluid phase »
In fluid phase On immobilized Ig
C3+FB+FD'
IgG'of'pa/ents'with' normal'and'low'C3'level'
Purified IgG
Total purified Ig are able to enhance C3 convertase activity
C3+B+D +purified IgG
SLIDE 16
The capacity of Ig to enhance C3 convertase activity but not anti- complement antibodies activity drive complement biomarkers
n=11 n=29
SLIDE 17
Polyclonal(Ig( Monoclonal(Ig(
0(((((25((((((50( 0(((((25((((((50( FB#(ng)#
α" α" α" β" β"
G20
Role of the monoclonal Ig in C3 convertase overactivation
C3-Activating IgG Non C3-activating IgG Polyclonal Ig Monoclonal Ig
Purification of monoclonal component by chromatography
Different elution fractions
G12 G20 G40 G56 1 2 3
α' /beta ratio
Ig monoclonale Ig polyclonales
SLIDE 18
Impact of hematological response on C3 convertase activity in vitro and complement biomarkers
C3 level significantly increased in patients who reached hematological response
at diagnosis after HR 0.0 0.5 1.0 1.5 2.0
α'/beta ratio
*
G5 G37 G53
Capacity of total Ig to enhance C3 convertase is decresad
SLIDE 19
Impact of Hematological response on renal outcomes
Chauvet et al. Blood 2017
SLIDE 20
Mechanisms of TMA in the setting of MIg are heterogeneous
cryoglobulinemia POEMS
Drugs* Post infectious HUS
Complement overactivation? ADAMTS13 deficiency Undetermined?
TMA and MIg
* Proteasome inhibitors
Bone marrow Tx Secondary HUS TTP aHUS Other..
Is MIg the main cause, a second hit or an aggravating factor in TMA??
SLIDE 21
Ravindran et al. Kidney Int 2017
146 patients with TMA 20 patients with MIg
Causes of TMA in the setting of MIg are heterogeneous
What is the role of the MIg? What is the mechanism of endothelial damage?
SLIDE 22
HUS and MIg: a complement mediated disease?
- 45 years
- purpura and severe distal angiopathy
- anemia, thrombocytopenia and acute renal failure
Diagnosis of Atypical HUS in the setting of Monoclonal IgA kappa No genetic variant in complement genes but positive for anti-FH IgA
IgA
Rigothier et al. AJKD 2015
SLIDE 23
Role of the monoclonal IgA on complement activation on cell surface
activated HUVEC
C3 deposition Count
10 10
1
10
2
10
3
10
4
20 40 60 80
Increase of complement activation on endothelial in presence of patient sera.
Rigothier et al. AJKD 2015
C3
SLIDE 24
C3 Glomerulopathy and atypical HUS associated with MIg Summary
MIg-C3G MIg-aHUS Epidemiological association ✓ 13 times more frequent ✓ 5-6 times more frequent Clinical arguments ✓ More severe disease ✓ More severe disease Therapeutic arguments ✓ Improvement with HR ✘ Complement mediated disease ✓ ✓ Role of the MIg in complement AP
- veractivation
✓ ✘ To determin
SLIDE 25