Transcript The biochemistry and genetics of autoimmune disease

The biochemistry and genetics
of autoimmune disease
Mcb5255 2015
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Autoimmunity vs Autoimmune
disease
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Autoimmunity: self recognition by the immune
response
◦ Dual recognition (self-MHC plus antigenic peptide)
◦ Jerne network hypothesis
◦ “don’t eat me” signaling (CD47 on erythrocytes)
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Autoimmune disease: self recognition with
damaging consequences to tissue function
◦ Tissue specific (e.g. T1D)
◦ Systemic (SLE)
Hypersensitivities
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4 main hypersensitivities (I-IV)
◦ Type I Anaphalaxis; Immediate; IgE mediated mast
cell degranulation
 Allergies, atopy
◦ Type II Cytotoxic (IgM and IgG mediated)
 Erythroblastosis fetalis, autoimmune hemolytic anemia,
pemphigus vulgaris
◦ Type III Immune complex
 Serum sickness, RA,
◦ Type IV DTH/contact sensitivity
 Contact dermatitis, T1D, RA, Multiple sclerosis
Figure 10-2
Figure 10-1
Tolerance
◦ Discrimination of self vs non-self
 Central tolerance develops in thymus and bone marrow
 (negative selection to eliminate cells reactive with antigens
 Present soon after cell expresses antigen receptor
 Present at high concentration over long periods of time
 Peripheral tolerance/anergy
 When cells encounter antigen in the absence of costimulatory signals that are usually provided by
inflammation
 Antigen segregation
 Physical barriers to restrict immune cell access
 Thyroid, pancreas, intracellular
 Regulatory cells that suppress responses
 Clonal deletion post activation
Differentiation of autoimmune
diseases; organ specific vs systemic
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Organ specific
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T1D
Multiple sclerosis
Grave’s disease
Autoimmune hemolytic anemia
Myasthenia gravis
Systemic
◦ RA
◦ Scleroderma
◦ SLE
Examples of autoimmune disease that can be
transferred across the placenta
disease
autoantibody
Symptom
Myesthenia gravis
Anti-acetylcholine receptor
Muscle weakness
Graves disease
Anti-thyroid stimulating
hormone receptor
Hyperthyroidism
Thrombocytopenic propura
Anti-platelet antibodies
Bruises and hemorrhaging
Pemphigus vulgaris
Anti-desmoglein
Blistering rash
Components of immunity that are
part of autoimmune disease
Disease
T cells
B cells
Antibody
SLE
Pathogenic help for
antibody
Present antigen to T
cells
Pathogenic
T1D
Pathogenic
Present antigens to T
cells
Present but unclear
role
Myesthenia gravis
Help for antibody
Antibody secretion
Pathogenic
Multiple sclerosis
Pathogenic
Present antigen to T
cells
Present but unclear
role
Routes to Autoimmune Disease
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Pathogens
◦ Cross-reactive antigens/molecular mimicry
 Lyme arthritis
 Rheumatic fever
◦ Chronic inflammation, immune dysregulation
◦ Disruption of cell/tissue barriers
 Sympathetic ophthalmia (granulomatous uveitis)
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Toxicants and other stressors
Genetic predisposition
Combinations of the above
http://pubs.acs.org/doi/pdf/10.1021/tx9003787
(see class website for link)
Figure 10-28 part 1 of 2
Figure 10-28 part 2 of 2
Genes involved in autoimmune
disease
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Single gene models
◦ Fas, FasL; ALPS (defects in apoptosis,
lymphoaccumulation, angergy and SLE-like autoimmune
disease)
◦ Mev; viable motheaten, Hcph-1; SHP1 (chronic
inflammation)
◦ IPEX immune dysregulation X linked recessive mutation in
transcription factor FoxP3; severe allergic inflammation,
hemolytic anemia, thrombocytopenia, etc.
◦ Deficiency in CD25 (IL2R); impaired peripheral tolerance
◦ CTLA4 mutation; Graves disease, T1D, etc.
◦ C1q mutation SLE
◦ MHC associations with autoimmune disease (e.g. HLAB27)
Mutations at the Motheaten Locus are
Within the Hcph Gene
Function of SHP-1
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Negative regulator of signal transduction
◦ growth factor receptors: c-kit, EPO
◦ activation signaling: BCR, TCR, NK activating receptor
◦ SHP-1 inactivates anti-apoptotic signaling molecules
in neutrophil proliferation
◦ induces apoptosis in sympathetic neurons
Clinical disease in viable motheaten mice
• Anemia
• Immunodeficiency
• Autoimmunity
• Death from acidophilic
macrophage pneumonia
Macrophage pneumonia in mev/mev mice
+/?
mev/mev
Approaches to identifying genes
involved in autoimmune disease
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GWAS genome wide associational studies
Family studies to identify SNP that track with
autoimmune disease
Animal models with mutations in candidate
genes
Meta-analysis of data to enlarge patient
populations studied for autoimmune disease
Biochemistry of autoimmune
disease
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Biochemical events that potentiate
autoimmunity
◦ events that cause damage to membrane, etc
 Reactive oxygen, chronic inflammation
 Biochemistry of damaging events associated with
autoimmune disease

Reactive oxygen, chronic inflammation
Oxidative Stress
SIGMA-ALDRICH
Figure 1. Pathogenesis of diabetic microvascular complications. This schematic proposes that the development of microvascular
complications begins early in the course of diabetes, well before clinical diabetes is detected. Certain genetic characteristics
or polymorphisms (Apo E4, Aldose reductase, ACE) may increase individual predisposition for development of microvascular
complications of diabetes [30,31], whereas other genetic factors, such as the toll receptor, are protective and decrease
predisposition. The various inflammatory mediators listed under the heading of inflammation cause direct cellular injury and
initiate the cycle of functional and progressive pathologic changes, which ultimately manifest as microvascular complications
[13,15–18,21]. As the disease progresses, lipotoxicity [28], glucotoxicity [42,43], and epigenetic factors further contribute to the
functional and pathologic changes. Intervention with insulin or insulin sensitizers, particularly in the early stages of pathogenesis,
can counteract inflammatory changes, control glycemia, prevent formation of advanced glycation end products, and ameliorate
oxidative-stress-induced overactivation of poly adenosine diphosphate ribose polymerase (PARP), with the potential to change
the natural history of microvascular complications [29,37]. ApoE4 = Apolipoprotein E4; ACE = Angiotensin-converting enzyme;
PKCβ = Protein kinase C beta; IL-6 = Interleukin-6; TNFα = Tumor necrosis factor alpha; NFκ B = Nuclear factor kappa B. Adapted
with permission from Vinik A, Mehrbyan A. Diabetic neuropathies. Med Clin North Am 2004; 88: 947–999
http://onlinelibrary.wiley.com/doi/10.1002/dmrr.530/pdf
Diabetes Metab Res Rev 2005; 21: 85–90.
http://nihroadmap.nih.gov/epigenomics/epigeneticmechanisms.asp
Histone modifications
http://www.nature.com/nsmb/journal/v14/n11/images/nsmb1337-F1.gif
http://www.cellsignal.com/reference/pathway/Histone_Methylation.html
Diabetes is not the only context in which histone
methylation is potentially important. For example:
•H3K4me3 demethylases : link between histone modifications and XLMR.
X-linked mental retardation (XLMR) gene SMCX (JARID1C),
which encodes a JmjC-domain protein, reversed H3K4me3 to
di- and mono- but not unmethylated products//Cell 2007
•The putative oncogene GASC1 demethylates tri- and dimethylated
lysine 9 on histone H3//Nature (2006) 442: 307-11.
•Sustained JNK1 activation is associated with altered histone H3
methylations in human liver cancer. //J Hepatol. 2009, 50: 323-33
•Perturbation of epigenetic status by toxicants//
Toxicology LettersVolume 149, Issues 1-3, 1 April 2004, Pages 51-58
Type 1 diabetes, which was previously called insulin-dependent
diabetes mellitus (IDDM) or juvenile-onset diabetes, may account for 5%
to 10% of all diagnosed cases of diabetes.
Type 2 diabetes, which was previously called non-insulin-dependent
diabetes mellitus (NIDDM) or adult-onset diabetes, may account for
about 90% to 95% of all diagnosed cases of diabetes.
Gestational diabetes is a type of diabetes that only pregnant women
get. If not treated, it can cause problems for mothers and babies.
Gestational diabetes develops in 2% to 5% of all pregnancies but usually
disappears when a pregnancy is over.
Other specific types of diabetes resulting from specific genetic
syndromes, surgery, drugs, malnutrition, infections, and other illnesses
may account for 1% to 2% of all diagnosed cases of diabetes.
http://www.cdc.gov/diabetes/consumer/learn.htm
Rate of new cases of type 1 and type 2 diabetes
among youth aged <20 years, by race/ethnicity,
2002–2003
<10 years
10–19 years
CDC. National Diabetes Fact Sheet, 2007.
Source: SEARCH for Diabetes in Youth Study
NHW=Non-Hispanic whites; AA=African Americans; H=Hispanics; API=Asians/Pacific Islanders; AI=A
Indians
Humanized mouse models
Humanized mouse models to study human diseases Brehm et al.
NOD/SCID/Akita mouse
Metal mediated autoimmune
disease
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Mercury-Induced Autoimmunity in Mice
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Jesper Bo Nielsen and Per Hultman
Environmental Health Perspectives • VOLUME 110 | SUPPLEMENT 5 | OCTOBER
2002
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Mercury induced autoimmunity
in mice
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-Genetically determined susceptibility is linked to the murine H-2 haplotype, and a susceptible
haplotype is a prerequisite for an autoimmune response expressed as antifibrillarin
antibodies.
Because haplotypes H-2t4 and H-2s confer susceptibility to mercury-induced autoimmune
response to a comparable extent, whereas H-2t1 causes resistance, our data suggest that
susceptibility may be restricted to the Aα and Aβ loci in H-2.
Different quantitative autoimmune responses were observed among susceptible mouse
strains with identical H-2 haplotype. We conclude that induction and development of AFA may
be modulated by mercury toxicokinetics, but non-H-2 genes may also modulate this response
independent of kinetics.
AFA and IgE are both important markers for adverse immune reactions after exposure to
mercuric chloride, but the responses are probably mechanistically unrelated.
Thresholds exist below which no autoimmune response is observed even after prolonged
exposure. At low mercury exposures, autoimmune response is not observed within the first
weeks but develops gradually. This observation is probably caused by mercury accumulation
in whole body and target organs along with increased exposure time.
The autoimmune response depends on gender. Female mice have a higher sensitivity (lower
threshold for induction of AFA) as well as a higher responsivity (lower WBR to reach 100%
autoimmune response) than male mice.
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The experimental model for induction of autoimmune responses demonstrates good
agreement with observations from human autoimmune diseases.
Exposure to inorganic mercury in
vivo attenuates extrinsic
apoptotic signaling in
Staphylococcal aureus enterotoxin B
stimulated T-cells
Michael D. Laiosa*, Kevin G. Eckles*,
Margaret Langdon*, Allen J.
Rosenspire†, and Michael
J. McCabe Jr.*
Toxicol Appl Pharmacol. 2007 December 15; 225(3): 238–250.
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http://ghr.nlm.nih.gov/handbook/illustrations/apoptosismacrophage
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http://cbm.msoe.edu/scienceOlympiad/module2012/apoptosis.html
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How does Hg influence the progression to
autoimmune disease?
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Previous work:
Low concentrations of Hg
attenuate CD95 (Fas) dependent
apoptosis
SEB attenuates Vb8
expansion Hg has little effect
on termination phase of
response at 72 hrs
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SEB is a
Superantigen
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Hg attenuates Caspase
activation
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Conclusion: Hg blocks caspace induction that is critical for apoptosis and
leads to accumulation of cells that would otherwise be deleted
Accumulation of autoreactive cells?
Accumulation of cells that then die by necrosis?
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Your presentations
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Each presentation is ~1 hour
Spend first 20 minutes or so describing the
fundamental information: what do we need to
know to understand the papers you have
assigned? How does this presentation fit into
the course main topic?
Divide the second 30 minutes into discussions
of each of the two contemporary papers that
you assigned to the class at the previous class
period
Grantsmanship:
NIH Steps to the NIH grant application
process http://funding.niaid.nih.gov/researchfunding/grant/pages/apply
ing.aspx
NIH electronic grant forms
http://grants.nih.gov/grants/funding/424/index.htm
Examples of outstanding titles and abstacts
http://funding.niaid.nih.gov/researchfunding/grant/pages/titleabs.aspx
Search engine for currently funded grants
http://projectreporter.nih.gov/reporter.cfm
Tongue-in-cheek": how to fail in grant writing
http://chronicle.com/article/How-to-Fail-in-Grant-Writing/125620/
Discussion points to include
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What is the fundamental hypothesis that is
being tested?
What techniques did they use that we have to
understand to evaluate the data?
What are the most important figures/data sets
that we should discuss?
Are there alternative interpretations of their
data?
What conclusions did they reach?
What new questions do they open up with
their results?
Grant application
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Hypothesis and ONE specific aim are due
March 5
We will discuss all specific aims on march 4th
Grant is due May 4th
Grant format:
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TEXT:
Hypothesis and specific aim (0.5 page)
Background and Significance (3-4 pages)
◦ What do we know about the system?
◦ What makes this hypothesis tenable?
◦ How is the approach you propose innovative?
Research designs and Experimental approach (4-5
pages)
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Rationale
Experimental design and methods
Anticipated outcomes
Potential pitfalls and alternative approaches
We will talk about NIH forms later in the semester
Student presentation schedule
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1.
Mechanisms of danger-signal mediated immune modulation
(Bevan) (March 11)
2.
MT and type I diabetes (Dawei) (March 11)
3.
Bacterial stress response proteins and their influence on the
immune response (Amy) (April 1)
4.
Chemical toxicants and their roles in chronic inflammation
(Kristen) (April8)
5.
Inflammation of the brain (Frances) (April8)
6.
The chemistry of stress: the role of reactive oxygen and nitrogen
species in inflammation and stress, and the management of ROS and
RNS in stress (Matthew) (April 15)
7.
Molecular indicators of stress as indicators of immune status
(Amanda) (April 22)
8.
Stress response proteins and their roles as vaccine adjuvants
(Brandon) (April 22)
9.
The interplay of infection, stress and the immune response
(Abraham) (April 29)
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