Current concepts of autoimmune bullous diseases

Advances in pathogenesis

Luca Borradori

Dept. of Dermatology

Inselspital, University Hospital of Berne

Switzerland Luca.Borradori@insel.ch

Autoimmune bullous

diseases Bullous pemphigoid

Autoimmune bullous diseases

Bullous pemphigoid

Autoimmunbullöse

Erkrankungen

Pemphigus vulgaris

Autoimmune blistering diseases of the skin

1. Heterogeneous group of diseases with substantial clinical overlap

associated with blistering of skin and/or mucosae

2. Humoral and cellular autoimmune response to disease-specific

target antigens

3. Targeted auto-antigens: molecular components of adhesion

complexes critical for skin integrity (and beyond…)

4. The same targeted antigens are defective in distinct inherited skin

diseases associated with skin fragility, blistering (e.g. epidermolysis

bullosa group), palmoplantar keratoderma, or ectodermal dysplasia

Major adhesion complexes in epidermis and other stratified

epithelia as disease targets of autoimmune bullous disease

Desmosomes

Cell-cell

adhesion complexes

Hemidesmosomes

Junctional adhesion

complexes

Kottke MD et al. J Cell Science 2006

Autoimmune bullous diseases: major groups

1. Diseases with intraepidermal blistering

Loss of cell-cell adhesion

Pemphigus group

2. Diseases with subepidermal blistering

Dermo-epithelial dysadhesion

Pemphigoid group

Mucous membrane pemphigoid

Epidermolysis bullosa acquisita

(Dermatitis herpetiformis)

3. Diseases with “mixed“ type of blistering

Paraneoplastic pemphigus (PNP)

Bullous pemphigoid - Key points

2. Subepidermal blistering with a dermal

neutrophilic and eosinophilic infiltrate

DIF

3. Linear deposits of IgG and/or C3 along the

epidermal basement membrane zone

4. Autoantibodies and autoreactive T cell

response to BP180 and BP230, two

components of hemidesmosomes

Di Zenzo G et al. Clin Dermatol. 2012 30 :3-16.

1. Most frequent autoimmune subepidermal bullous

disease in Europe

• Elderly affected

• Rarely in childhood

ANCHORING

FIBRILS

Collagen VII

Laminin 332

6

BP

180

BP230

4 a6

PLECTIN

BP

Auto-Abs

TARGETS

ANCHORING

FILAMENTS

BASAL

KERATINOCYTE

BP180 et BP230, the target antigens of pemphigoids,

are components of hemidesmosomes

BP autoantibodies recognize multiple antigenic sites

on both BP180 and BP230

COOH

ECD

NH2

Extracellular

Domain (ECD)

Intracellular

Domain (ICD)

NC16A

Collagen 15

C-terminus

LAD-1

BP180

B C

Globular head Rod Globular

repeats

COOH NH2

FP-3A FP-7

rBP55

BP230-C

F G

N1 N2 N3 C1 C2

BP230-N BP230-C1

BP230

Di Zenzo & Borradori , Clin Dermatol 2011

Are BP autoantibodies directed

against BP180 (and BP230) pathogenic?

Pathogenic role of anti-BP180 autoantibodies

Transplacentar passage of anti-BP180 autoantibodies

in gestational pemphigoid causes transient blistering

in the newborn

Demonstration of pathogenic activity of

anti-BP180 auto-antibodies in murine models:

previous limitations

Human anti-BP180 auto-abs fail to

react with mouse BP180 and do

not reproduce bullous pemphigoid

in a passive transfer mouse model

Liu Z et al. J Clin Invest 1993; 92: 2480-8

Need for better models to assess the role of anti-BP180 auto-abs

Generation of BP180-humanized mice

(mBP180 -/- hBP180 +/+) (1)

Nishie W et al. Nature Med. 2007;11: 378-383

‘Humanized’ mice to test the pathogenicity of human anti-BP180 auto-antibodies

mBP180 -/-

mBP180 -/- hBP180 +/+

human BP180 murine BP180

mBP180-/- ,huBP180+/+

mBP180+/- TG-hBP180

Inactivation of

BP180 gene

Transgenic expression

of human BP180

Crossing

BP180-humanized mice injected with either purified anti-BP180 auto-abs or

with a mAb to human BP180 (NC16A) develop a BP-like phenotype

• Erythema and subepidermal blistering

Nishie W et al. Nature Med. 2007;11: 378-383; Li Q et al. J Immunol 2010; 185: 7746-7755

Anti-BP180 IgG auto-antibodies

are pathogenic

• Separation in the lamina lucida

• IgG auto-abs fixation at the DEJ

Blistering by human anti-BP180 abs depends on complement

and neutrophils in a humanized BP180-NC16A mouse model Liu Z et al. J Autoimm 2008; 31: 331-338

Mice depleted of neutrophils develop

no blistering with pathogenic abs

F(ab’)2 fragments of anti-BP180 abs fail

to trigger blistering in injected mice

Murine C3 Murine C3

Rag2-/-

Hum BP180+/+

humBP180-/-

Spleen (T cells & B cells etc.)

Immunization with

recombinant human BP180

No tolerance against human BP180

Transfer

Role of B and T cells in disease development:

active mouse model for bullous pemphigoid

Ujiie H et al. J Immunol 2010;184;2166-2174

Both B cells and CD4-positive T cells are required for disease initiation

in an active mouse model for bullous pemphigoid

Ujiie H et al. J Immunol 2010;184;2166-2174

Pathogenicity of anti-BP180 IgG autoantibodies : current model

DERMIS

DERMAL

VESSEL

IgG

EPIDERMIS

MC

MF

PMN

C3b C5a

BLISTER

FORMATION

Neutrophil

elastase a1-

proteinase

inhibitor

IL-8

MMP-9

IL-8

3

3

1

3

3

3

4 4

3

3

MMP-9

PMN

2

5

6

6

Di Zenzo et al. 2008

Production of autoantibodies, regulation by autoreactive T cells

Complement activation - Neutrophil migration and activation

Eosinophils and mast cells implicated (IgE autoantibodies)

Secretion and/or activation of plasmin, MMPs and neutrophil elastase

Damage of the dermo-epidermal junction

Pemphigus vulgaris / p. foliaceus - Key points

1. Autoimmune blistering diseases of the skin

and/or mucosae

– Start usually in adulthood

– Association with certain HLA class II alleles

– P. foliaceus: endemic areas in Brazil and North Africa

2. Intraepidermal blister formation (acantholysis)

3. Immune response to desmoglein 3 and/or desmoglein 1

4. Desmogleins: components of cell-cell adhesion complexes,

desmosomes Stanley & Amagai. NEJM 2006; 355:1800-1807

Mice without dsg 3 develop a phenotype of PV and hair loss

Dsg 3 -/-

Dsg 3 -/-

Role of dsg 3

promoting cell-cell adhesion

in normal hair structure (anchorage of telogen hair)

Koch PJ et al. JCB 1997; JCS 1998

Pemphigus auto-abs cause acantholysis and blistering in

passive transfer studies in mice

Auto-abs target epitopes on the N-terminus of dsg 3/1

within the cell adhesion surface region

Weakly pathogenic abs (only if combined)

Strongly pathogenic ab (alone)

Futei Y et al. J. Immunol. 2000

Sekiguchi M et al. J. Immunol. 2001

Tsunoda K et al. J. Immunol. 2003

Kawasaki H et al. JID 2006

Intracellular domain

cell

Steric hindrance hypothesis

Strongly pathogenic antibodies in pemphigus react with the

cell adhesion surface of desmogleins

Model of interaction of cadherins at the cell

surface Electronic tomographic mapping

of a desmosome

100 nm

Cellular membrane

He W. et al. Science 2003: 302: 109

Getsios S. et al. Nat Rev. 2004; 5: 271

Pemphigus - Mechanisms of acantholysis

Autoantibodies activate transmembrane

signaling pathways leading to an impaired

intercellular adhesion

Desmosome disassembly (phosphorylation)

Reorganization of the cytoskeleton

• actin and intermediate filaments

Impaired differentiation with increased

proliferation

Activated pathways…

• p38 MAPK

• Protein kinase C

• c.Myc proto-oncogene

• src, cdk2,…

Seishima et al. 1995 , Esaki et al. 1995 Caldelari

& Müller 2001, Williamson & Müller 2006, Cirillo

et al. 2007, Grando et al. 2007, Jolly SP et al.

2010

PV IgG-mediated signaling activates p38 MAPK with

reorganization of the cytoskeleton

Berkowitz P et al. JBC 2005

Berkowitz P et al. PNAS 2006

Waschke J et al., JCB 2006

Jolly PS et al JBC 2010

GTPase RhoA Phosph.

Inhibition of p38MAPK prevents clinical blistering

Perspectives: pharmacologic therapy of pemphigus ?

p38 MAPK inhibitors, including KC-706, currently evaluated

PV IgG

Rag2-/-

Dsg3+/+

Dsg3-/-

Spleen (T cells & B cells etc.)

PV mouse model : interaction between antigen-specific

B-T cells is required for disease development

Immunization with

rDsg3

No tolerance against Dsg3

Transfer

Erosions & hair loss Acantholytic blister IgG deposition

kindly provided by M. Amagai

Takashi et al. J Immunol 2009

Hertl M et coll. Marburg

IgG1

B-Cell

CD4+

T-Helper-cell

IL-4, IL-5

IL-13

Plasma-

cells

Rituximab

mechanisms of action

1. Depletion of CD20+ pre-B cells, B cells and memory B cells

• Reduction of anti-dsg antibodies (via BAFF increase ?)

2. Reappearance of naive B cells with a normal repertoire

3. Reduction of dsg-specific autoreactive T cells important for B

cell activation (B and T cell crosstalk) Mousquet et al. J

Invest Dermatol 2008; Eming et al. J Invest Dermatol 2008, Nagel et al. J Invest

Dermatol 2009

Advances in pathogenesis in AIBD

Take home messages and learning objectives

1. Group of rare diseases associated with autoantibodies directed

against structural components of adhesion complexes,

desmosomes and hemidesmosomes

• Targets of both acquired and inherited dermatoses

2. Advances in the understanding of mechanisms leading to blistering

• Bullous pemphigoid: inflammatorry cascade with activation of

complement, inflammatory cells, and proteases

• Pemphigus: steric hindrance, dsg-depleted desmosomes,

activation of signaling pathways