Lecture: Autoimmunity

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Lecture Autoimmunity Mark Anderson, MD,
PHD UCSF Diabetes Center manderson_at_diabetes.ucsf.e
du 415-502-8052
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Autoimmunity

• Definition immune response against self (auto-)
  antigen
• General principles
• Significant health burden, 5 of population
• Multiple factors contribute to autoimmunity,
  including genetic predisposition, infections
• Fundamental problem is the failure of
  self-tolerance
• Problems
• Failure to identify target antigens,
  heterogeneous disease manifestations, disease
  usually presents long after initiation

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Classification of Autoimmune Diseases

• Broadly separated by the type of effector
  mechanism (similar to hypersensitivity
  classification scheme)
• Three classes
• Type II Antibody against cell-surface antigen or
  matrix antigens
• Type III Immune-complex disease
• Type IV T cell-mediated disease

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Figure 11-1 part 1 of 3
Type II Antibody-mediated diseases
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Figure 11-5
Graves disease
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Figure 11-7
Graves diseaseProof that its antibody mediated
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Myasthenia Gravis

• In this disease, autoantibodies to the
  Acetylcholine receptor block neuromuscular
  transmission from cholinergic neurons by blocking
  the binding of acetylcholine and by causing
  downregulation (degradation) of its' receptor.

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Figure 11-1 part 2 of 3
Type III Immune-complex mediated diseases
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Figure 10-32
Review Immune complex formation
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Figure 11-10
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Systemic Lupus Erythematosus (SLE)

• Systemic diseases such as SLE and vasculitis
  almost certainly result from autoantibody-antigen
  complexes and their consequences. Circulating
  antibodies to constituents of the cell surface,
  cytoplasm, and nucleus
• Anti-DNA, anti-histone, anti-sRNP
• Certain organs are especially sensitive to immune
  complex deposition particularly the kidney. SLE
  patients possess a wide variety of autoantibodies
  to both cytoplasmic and nuclear antigens.
• The presence of IgG anti double- stranded DNA is
  characteristic of this condition (Note IgM
  anti-ds DNA is NOT pathogenic).
• Two significant facts point to the role of immune
  complexes in SLE.
• First, patients demonstrate significant depletion
  of complement (C3) and neutrophils resulting from
  activation by the complexes.
• Second, complement deficiencies which impair IC
  clearance (C1,C2 or C4, see lecture 10) are very
  strong predisposing factors for SLE.
• Symptoms include rash, arthritis,
  glomerulonephritis, vasculitis.

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Figure 13-33
SLE Immune complexes in the kidney
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Figure 11-1 part 3 of 3
Type IV T cell-mediated diseases
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T cell mediated effects (cellular immune)

• Direct T cell cytotoxicity via CD8 CTL
• Self-destruction of tissue cells induced by
  cytokines, eg, TNFa
• Recruitment and activation of macrophages leading
  to bystander tissue destruction
• Induction of target tissue apoptosis by the T
  cell membrane protein FasL

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Figure 11-8
Type I Diabetes a T cell-directed attack
against the b-cells of the pancreatic islet
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Type I Diabetes

• T cell response to antigens expressed in the
  b-cells of the islets
• Proinsulin/Insulin, GAD, I-A2
• T cell response is Th1 like, makes g-IFN and
  helps recruit a tissue/cell destruction response
• gt90 islet destruction needed for the disease to
  be expressed
• Patients also have autoantibodies to islet
  antigens

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Tetramers flow studies on PBMC
DR0401-MOG
DR0401-Control
DR3-proIns
DR3-Control
CD4
Tetramer
DR0402-desmoglien
DR0402-control
DRB4-GAD557I
DRB4-control
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Why do autoimmune diseases occur?

• Answer Failure in T cell tolerance

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Figure 13-16
Mechanisms of immune tolerance
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Overview of Autoimmunity
Failure of central or peripheral tolerance
Genetic Predisposition
Environmental Factors
CD4 T Cell Driving Force
Autoreactive B Cells
Specialized cells present self-tissueproteins
Autoantibodies
IFN-gamma IL-2, etc.
Tissue injury release of self antigens activatio
n of self-reactive lymphocytes
CD8 T Cell Driving Force
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Because Autommunity is so complex, how can we
figure out how it happens?

• Answer
• Use genetics
• Animal models

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Genetic basis of autoimmunity

• Genetic predisposition of autoimmune diseases
• Increased incidence in twins
• Identification of disease-associated genes by
  breeding and genomic approaches
• Multiple genes are associated with autoimmunity
• No single mutation causes autoimmunity
• MHC genes
• Major genetic association with autoimmune
  diseases (relative risk)
• Disease-associated alleles may be found in normal
  individuals
• Non-MHC genes
• Many loci identified by genomic methods, animal
  studies
• Mutations in complement genes predispose to lupus

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HLA (or MHC) is the strongest genetic factor for
susceptibility to autoimmune disease
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Figure 13-21
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How does MHC predispose?
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Figure 13-23
DQ8 Diabetes-associated risk attributable to a
change in amino acid 57 of the beta chain, which
makes the groove more open.
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Susceptibility loci associated with autoimmunity
In black are loci associated with some autoimmune
diseases of mice Idd, insulin-dependent
diabetes Cia, collagen-induced arthritis Eae,
experimental autoimmune encephalomyelitis Sle,
systemic lupus erythematosus. In red are the
locations of selected genes of immunological
interest.
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Non-MHC genes associated with autoimmune disease
in HUMANS

• CTLA-4- polymorphism associated with type 1
  diabetes and thyroid disease
• PTPN22- phosphatase that binds to Csk in the T
  cell and B cell signaling pathways, associated
  with Lupus, Type 1 Diabetes, Rheumatoid arthritis
• NOD2- intracellular toll receptor associated with
  Crohns disease and Uveitis (eye autoimmunity)
• Complement genes in Lupus
• Single gene disorders AIRE, FoxP3, ALPS

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Animal models of autoimmunity

• NOD mouse- model of type 1 diabetes
• NZBxNZW mouse-model of Lupus
• KBxN mouse-model of rheumatoid arthritis
• EAE- induced model of multiple sclerosis whereby
  disease is induced by injecting proteins of the
  myelin sheath with adjuvant
• Knockouts that get autoimmunity

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Figure 13-3
Recent work in this model suggests Th17 cells are
important!
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Figure 13-17
NOD mouse spontaneously gets diabetes
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Figure 13-34
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B7.1/B7.2 KOs get worse diabetes in the NOD
background?
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Answer is Tregs, need B7s to generate Tregs
effectively
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Forward genetics to find autoimmune disease genes
Christopher C. Goodnow, Australia
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ENU screen finds a line with autoantibodies,
glomerulonephritis, and splenomegaly
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Mice have increased germinal centers and a defect
in a gene (Sanroque) that represses follicular T
cells
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What triggers autoimmune disease? Environment

• However, it is clear that environmental factors
  also play a role in autoimmune disease. If you
  examine how frequently identical twins both
  develop a disease (the concordance rate), it is
  only about 20-40 for common autoimmune diseases
  such as diabetes, SLE and rheumatoid arthritis.
  This makes it highly likely that environmental
  factors must also be important. While we might
  expect factors such as diet to play a role, we
  can postulate that infectious organisms are the
  most significant environmental factor.
• Why does the 40 concordance rate for diabetes in
  identical twins only make it very likely (rather
  than certain) that environmental factors play a
  role in triggering the disease?
• In a few cases we have evidence for a direct link
  between a specific infection and an autoimmune
  disease.
• The classical example is that of rheumatic fever
  following Streptococcal infection. More recently,
  persuasive evidence implicates infection with a
  variety of organisms (Yersinia, Shigella
  ,Chlamydia) and reactive arthritis (NB not
  rheumatoid). Nevertheless a causal link has been
  elusive in many other conditions for which the
  environmental factors must exist but remain
  unidentified (eg. diabetes).

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Environmental trigger like infection seems likely
for at least some
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Molecular Mimicry Hypothesis
11.29
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Mechanism of Rheumatic Fever
11.28
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Endocrine factors

• Most autoimmune disease do not occur with equal
  frequency in males and females. For example
  Graves' and Hashimoto's are 4-5 times, and SLE 10
  times, more common in females while Ankylosing
  Spondylitis is 3-4 more frequent in males.
  These differences are believed to be the result
  of hormonal influences
• A second well documented hormonal effect is the
  marked reduction in disease severity seen in many
  autoimmune conditions during pregnancy.
  Rheumatoid arthritis is perhaps the classic
  example of this effect. In some cases there is
  also a rapid exacerbation (rebound) after giving
  birth.

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Model of the importance of infection (Rip-LCMV
model)
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Treatment

• What would be the ideal way to treat autoimmune
  disease?
• Answer remove only the antigen-specific response

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Treatment (cont.)

• Reality Unable to remove the antigen-specific
  response in general
• Mainstay of treatment anti-inflammatories and
  global immunosuppression if symptoms are severe
  enough to warrant it

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Treatment

• Anti-inflammatory (corticosteroid) and
  immunosuppressive (cyclosporin) drug therapy is
  the present method of treating autoimmune
  diseases.

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TNF?

• Tumor Necrosis Factor-? (TNF-?)
• Identified in 1970s by Lloyd Old et al., as a
  serum factor that caused necrosis of some murine
  tumors.
• In the 1980s, studies into the role of TNF?
  intensified
• TNF? is a multifunctional pro-inflammatory
  mediator
• Induction of further cytokine production
• Activation or expression of adhesion molecules
• Growth stimulation
• TNF? action needs to be carefully controlled by
• the body

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TNF? Continued

• Mediates key roles in
• - acute and chronic inflammation
• - antitumor responses
• - infection
• Overproduction of TNF?? is associated with a
  wide range
• of pathological conditions.
• Effort to find ways to down-regulate production
  or
• inhibit its effects.

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Crohns Disease (CD)

• Inflammatory Bowel Disease (IBD)
• Chronic inflammation of areas of the
  gastrointestinal tract.
• Can affect all layers of the bowel wall with
  possible abscesses and fistulas (30 of
  patients).
• Common symptoms

Fever Fatigue
Loss of appetite
Excruciatingly painful may require
morphine Increased risk of colorectal
cancer Unknown cause No known cure
Abdominal pain
Weight Loss
Diarrhea
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Fistulas in Crohns Disease

• Crohns disease is complicated by development of
  fistulae in 30 of patients
• Fistulas An abnormal duct or passage that
  connects an abscess, cavity, or hollow organ to
  the body surface or to another organ
• Internal bowel to bowel, bowel to bladder, or
  rectovaginal
• Enterocutaneous extending through abdominal wall
  
• Difficult to treat

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Role of TNF? in Crohns Disease

• Imbalance of pro- and anti-inflammatory
  mediators
• Enhanced Th1 response (IFN?, TNF?)
• TNF? is a pro-inflammatory cytokine produced by
  monocytes, macrophages and T cells
• Local production is thought to have a key role
  in the initiation and propagation of Crohns
  disease
• Production of TNF? in the intestinal mucosa is
  increased in patients with Crohns disease
• Cytokines critical for generation of a Th1
  response are increased (TNF?, IFN?, Il-18, and
  Il-12)

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Biologics for Crohns Disease

• Introduction of Infliximab in 1998 heralded as
  the most important addition to therapy for this
  condition in 50 years. Even though the costs
  associated with a single dose are several
  thousand US dollars, more than 150,000 patients
  have received infusions since its approval
  (Valle, E., 2001).

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Results of Infliximab Use

• The use of Infliximab is usually restricted to
  patients who have severe disease, not responsive
  to conventional therapy.
• A single infusion can induce remission in 60
  of patients with active Crohns Disease (Targan
  et al., 1997).
• Three infusions over six weeks led to closure of
  fistulae in 50 of patients (Present et al.,
  1999).
• Repeated infusions maintains remission in gt60
  of patients (Hanauer et al., 2002).

Figure Closure of an abdominal fistula in a
60-year old man with treatment of Infliximab
(5mg/kg). Present et al., 1999.
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Rheumatoid Arthritis

• RA, a new disease
• Ethnic group with highest RA is North American
  Indians (NAI)
• Infectious etiology and/or genetic
  susceptibility?
• Caucasians RA 1, often skips generations
• Higher in NAI, but varies with the tribe, present
  in every generation
• Female to male ratio of RA is 73

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La Familia de Jordaens en un Jadin, by Jacob
Jordaens (c 1630)
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Autoantigens - Ubiquitous

• IgG Fc
• Citrulline containing peptides (CCP)
• Filaggrin, Keratin, Perinuclear factor, Sa
• ANCA, ANA
• Glucose-6-phospnate isomerase (GPI)
• Calreticulin
• Others.but not DNA

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Figure 11-13
Rheumatoid Arthritis Treatment with anti-TNFa
(TNF is an inflammatory cytokine made by T cells)
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Abrams JR, et al. Blockade of T lymphocyte
costimulation with cytotoxic T lymphocyte-associat
ed antigen 4- immunoglobulin (CTLA4Ig) reverses
the cellular pathology of psoriatic plaques,
including the activation of keratinocytes,
dendritic cells, and endothelial cells.J Exp
Med. 2000 Sep 4192(5)681-94.
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Type 1 Diabetes - A Disease of the Immune System
Type 1 Diabetes is caused by the
autoimmune destruction of insulin producing
ß-cells
TCR
antigen
T Cell
T Cell
ß-cells
T-cells mediated killing of ß-cells
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Progression in Type 1 Diabetes
Genetic


Environmental


Predisposition
Insult
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AutoAbs
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Beta Cell
Mass
Abnormal IVGTT
50
25
Clinical Diagnosis
Honeymoon
10
Years
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Checkpoints in the development of autoimmune
diabetes
Checkpoint 1
Insulitis -Starts at weaning immunological
changes related to food uptake and changes in
the intestinal flora -Increased homing of T cells
expression of addressins MadCam and PNAd on
pancreatic blood vessel epithelium
Checkpoint 2
Beta cell loss and diabetes - T cells gain more
aggressive effector mechanisms Th1/Th2 balance,
cytokines, Expression of Fas Ligand on CTLs -
Loss of protective mechanisms Protective
cytokines, Regulatory cells - Amplification
Epitope spreading
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Anti-CD3 mAb Treatment for Autoimmunity
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Suppression of autoimmunity with anti-CD3
DIABETES
Need to give at disease onset!
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Results of Herold anti-CD3 Phase I/II trial in
Type 1 Diabetes

• Study Protocol
• New onset Type 1 diabetes mellitus in stable
  metabolic condition
• Within the first 6 weeks since diagnosis
• Age 8 35
• Two week single treatment with increasing doses
  of anti-CD3 mAbs 5 mg ? 4 mg/dose.
• 23 treated patients and 23 control subjects
  undergoing metabolic studies over 2 years

Drug tx
150
1
Control



0.8


100
0.6

AUC (pmol/ml/240min)
Insulin dose (U/Kg)
0.4
50
0.2
0
0
0
6
12
18
24
0
6
12
18
24
Month
Month
p0.003 vs control
plt0.02 vs control
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Can antigen-specific Tregs be expandedfrom NOD
mice?
rHuIL-2 1-2000U/ml
gt 98 purity

• Use peptide-MHC/anti-CD28 beads
• to expand antigen-specific T regs

p31-I-Ag7-dimers
Anti-CD28
Class II a chain
peptide
Class II b chain
linker

• high activity peptide mimotopes identified for
  BDC TCR
• P1 P2 P3 P4 P5 P6 P7 P8 P9 EC50
• p31 Y V R P L W V R M E 0.7 nM

Leucine zipper
Hinge region
Fc of IgG2a
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p31-Tregs exhibit bystander suppression in vitro
GAD286 stimulated
GAD286 p31 stimulated
CPM
APC
APC
P31-Tregs
P31-Tregs
GAD286 repsonders p31-Tregs
GAD286 repsonders p31-Tregs
GAD286 Tg responder
GAD286 Tg responder
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Suppression of Diabetes in CD28KO mice by p31
GAD-IAg7/anti-CD28 expanded NOD Tregs
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Emerging agents (in combination?)
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Mechanisms of Tolerance
T cell
CD28
Normal T cell response
Activated T cells
TCR
T cell
Co-stimulation Blockade
TCR
CTLA-4/PD-1
Negative Signaling
Functional unresponsiveness
TCR
Fas
Apoptosis/AICD
TCR
T cell
Regulatory cytokines
CD28
Regulation
TCR
Regulatory T cells and DC