Download Understanding Lupus

Understanding Lupus
OR
Why Rheumatology Is So Cool.
MICHELLE KAHLENBERG
SENIOR TALK
M A R C H 1 9 TH/ 2 0 TH 2 0 0 9
Why is lupus such a mystery to us?
 Unlike many other autoimmune diseases, it affects
many organs with varying disease manifestations
over time.
 This makes it difficult to diagnose: average is 4 years
and 3 different doctors
 There are all those antibodies to know…
 Treatments are OLD with significant side effects
Talk Overview
 Discuss Lupus diagnostic criteria and clinical
manifestations
 Explore Mechanisms of Lupus (cool!)
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Defective apoptosis
IFN-a
TLR signaling
B-cell disregulation
Pathology of autoantibodies
 Discuss how research into understanding the
mechanisms of SLE is advancing treatment for lupus
Lupus Diagnostic Criteria (need 4)
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1. Malar Rash: Fixed erythema, flat or raised, over the malar eminences, tending to spare the nasolabial folds
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2. Discoid rash: Erythematous raised patches with adherent keratotic scaling and follicular plugging; atrophic
scarring may occur in older lesions
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3. Photosensitivity: Skin rash as a result of unusual reaction to sunlight, by patient history or physician
observation
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4. Oral ulcers: Oral or nasopharyngeal ulceration, usually painless, observed by physician
From http://www.rheumatology.org/publications/classification/SLE/1997UpdateOf1982RevisedCriteriaClassificationSLE.asp?aud=pat
Lupus Diagnostic Criteria (need 4)
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5. Nonerosive Arthritis: Involving 2 or more peripheral joints, characterized by tenderness,
swelling, or effusion
6. Pleuritis or Pericarditis: a) Pleuritis--convincing history of pleuritic pain or rubbing heard by
a physician or evidence of pleural effusion OR b) Pericarditis--documented by electrocardigram
or rub or evidence of pericardial effusion
7. Renal Disorder: a) Persistent proteinuria > 0.5 grams per day or > than 3+ if quantitation not
performed OR b) Cellular casts--may be red cell, hemoglobin, granular, tubular, or mixed
8. Neurologic Disorder: a) Seizures--in the absence of offending drugs or known metabolic
derangements; e.g., uremia, ketoacidosis, or electrolyte imbalance OR b) Psychosis--in the
absence of offending drugs or known metabolic derangements, e.g., uremia, ketoacidosis, or
electrolyte imbalance
9. Hematologic
Disorder: a) Hemolytic anemia--with reticulocytosis
OR b) Leukopenia--<
3
3
4,000/mm on ≥ 2 occasions OR c) Lymphopenia--<
1,500/ mm on ≥ 2 occasions OR d)
3
Thrombocytopenia--<100,000/ mm in the absence of offending drugs
10. Immunologic Disorder: a) Anti-DNA: antibody to native DNA in abnormal titer OR b) AntiSm: presence of antibody to Sm nuclear antigen OR c) Positive finding of antiphospholipid
antibodies on: an abnormal serum level of IgG or IgM anticardiolipin antibodies, a positive test
result for lupus anticoagulant using a standard method, or a false-positive test result for at least
6 months confirmed by Treponema pallidum immobilization or fluorescent treponemal
antibody absorption test
11. Positive Antinuclear Antibody: An abnormal titer of antinuclear antibody by
immunofluorescence or an equivalent assay at any point in time and in the absence of drugs
From http://www.rheumatology.org/publications/classification/SLE/1997UpdateOf1982RevisedCriteriaClassificationSLE.asp?aud=pat
Arthritis
 Painful joints are #1 symptom in 76-100% of patients
 With or without signs of inflammation, mild effusions if any
 Usually involve hands, wrists, knees
 Can be asymmetric
 Generalized myalgias particularly deltoids and quads
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<15% with elevations in CPK
Nephritis
 Very closely linked with prognosis
 5- and 10-year survival rates are documented as high as 85%
and 73%, respectively (used to be about 0% before
immunosuppressants)
 Diagnosed by presence of proteinuria (>500mg/24
hours)
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Watch for symptoms of edema, puffy eyes, frequent urination.
 Biopsy helpful to determine whether aggressive
treatment is required
 Associated HTN needs aggressive Rx with ACE/ARB
Nephritis
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Class I Minimal mesangial lupus nephritis
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Normal glomeruli by light microscopy, but mesangial immune deposits by immunofluorescence
Class II Mesangial proliferative lupus nephritis
Purely mesangial hypercellularity of any degree or mesangial matrix expansion by lightmicroscopy, with mesangial immune deposits
May be a few isolated subepithelial or subendothelial deposits visible by immunofluorescence or electron microscopy, but not by light microscopy
Class III Focal lupus nephritis
a
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Active or inactive focal, segmental or global endo- or extracapillary glomerulonephritis involving 50% of all glomeruli, typically with focal subendothelial
immune deposits, with or without mesangial alterations
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Class IV Diffuse lupus nephritis
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Class IV-S (A) Active lesions: diffuse segmental proliferative lupus nephritis
Class IV-G (A) Active lesions: diffuse global proliferative lupus nephritis
Class IV-S
(A/C)
Active and chronic lesions: diffuse segmental proliferative and sclerosing lupus nephritis
Active and chronic lesions: diffuse global proliferative and sclerosing lupus nephritis
Class IV-S (C) Chronic inactive lesions with scars: diffuse segmental sclerosing lupus nephritis
Class IV-G (C) Chronic inactive lesions with scars: diffuse global sclerosing lupus nephritis
Class V Membranous lupus nephritis
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b
Active or inactive diffuse, segmental or global endo- or extracapillary glomerulonephritis involving 50% of all glomeruli, typically with diffuse
subendothelial immune deposits, with or without mesangial alterations. This class is divided into diffuse segmental(IV-S) lupus nephritis when 50% of the
involved glomeruli have segmental lesions, and diffuse global (IV-G) lupus nephritis when 50% of the involved glomeruli have global lesions. Segmental is
defined as a glomerular lesion that involves less than half of the glomerular tuft. This class includes cases with diffuse wire loop deposits but with little or
no glomerular proliferation
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Class III (A) Active lesions: focal proliferative lupus nephritis
Class III (A/C) Active and chronic lesions: focal proliferative and sclerosing lupus nephritis
Class III (C) Chronic inactive lesions with glomerular scars: focal sclerosing lupus nephritis
Global or segmental subepithelial immune deposits or their morphologic sequelae by light microscopy and by immunofluorescence or electron
microscopy, with or without mesangial alterations
Class V lupus nephritis may occur in combination with class III or IV in which case both will be diagnosed
Class VI Advanced sclerosis lupus nephritis
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90% of glomeruli globally sclerosed without residual activity
Table from Weening et al., J Am Soc Nephrol 15: 241–250, 2004
Nephritis
 Class I-no Rx
 Class II-Rx if proteinuria >1000 mg/d
 Class III and IV at high risk of progression so require
aggressive immunosuppressive therapy
 Class V Rx with steroids
 Class VI-dialysis or transplant
Nervous System
 Headache is the most common complaint
 ADD, mood disorders, anxiety, delirium, psychosis,
seizures (generalized or partial)
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Difficult to prove absolute causality
 Generalized encephalopathies
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Formal neuropsychiatric testing reveals deficits in 21-67% of patients
with SLE
 Cerebritis
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Degenerative changes in small vessel walls, often with minimal or no
inflammatory infiltrates
May be related to immune complex deposition
 Neuropathy secondary to vasculitis of vasa nervorum
(often with dermatomyositis overlap)
CV System
 Pericarditis 6-45% of patients: low likelihood of tamponade or constrictive type.
 <10% with myocarditis
 Libman-Sacks endocarditis
 1-4 mm vegetations of accumulations of immune complexes and mononuclear cells on mitral,
tricuspid or aortic valves
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Risk of thromboembolism or secondary infective endocarditis (abx prophy)
 Aortic insufficiency is the most common valvular abnormality.
 Heart disease
 Contributes to bimodal pattern of mortality from lupus
 A study from U of Pittsburgh comparing rates of MI to that of Framingham Offspring Study data
showed that risk of MI was 50x higher in woman with lupus ages 35-44 and 2.5-4x higher in older
age groups
 Autopsy data shows CAD in 40% of SLE patients as opposed to only 2% of age matched controls.
 Atherosclerotic plaque burden (via carotid intima media thickness measurements and by coronary
calcium scores) is higher in patients with SLE than in controls
 “Lupus dyslipoproteinemia” is low HDL, high TG, normal or only slightly elevated LDL, increased
lipoprotein(a): this appears to correlate with disease activity
 Means of prevention focus on risk factor management and inflammation control, but no clear
guidelines are available as of yet.
Lungs and Pleura
 Over 30% will have pleuritis or an effusion over the
course of their disease
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Fluid is exudative, normal glucose, high protein, WBC <10,000
(neutrophilic or lymphocytic), decreased complement
 Can have pneumonitis, pulmonary hemorrhage (rare
but often fatal), PE, pulmonary HTN
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Pulmonary HTN more likely to be associated with Raynaud’s
Hematologic System
 Chronic anemia is present in up to 80% of patients
 Leukopenia is present in up to 50% of patients
(lymphopenia more common than neutropenia).
 Thrombocytopenia ranges from modest to severe
with bleeding complications
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May reflect disease activity
May be first sign of SLE; predating other signs and symptoms
by years.
Associated with the presence of anti-platelet antibodies
 Secondary APS seen in about 40% of patients with
SLE
BUT WHAT CAUSES ALL OF THESE
SYMPTOMS?
B cell differentiation:
-negative selection of autoreactive cells in
bone marrow (90%)
-migration to LN
-somatic hypermutation
-survival by positive selection
-requires numerous co-stimulatory
interactions with APC and T cells
(including upregulation of BAFF and IFN-a)
Image from Niiro and Clark, Nature Reviews Immunology 2, 945 - 956
Defective clearance of apoptotic cells
 One common theme is defects in clearance of
apoptotic cells resulting in autoantibody production
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Phagocytes from lupus patients engulf far less during a 7 day
period in vitro than phagocytes from healthy patients
Image from Trouw et al., Mol Immunology (2008) 45:1203
Defective clearance of apoptotic cells
 There may be a genetic component to defective
apoptosis.
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Concordance is 25% among monozygotic twins but only 2% among
dizygotic twins suggesting a genetic component
HLA-DR2 and HLA-DR3 confer relative risk of 2-5.
C1q deficiency results in high likelihood of developing SLE
Complement C4a deficiency: 80% of people with SLE have at least
one null allele
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Can lead to decreased clearance of apoptotic cells and increased
inflammation and presentation of self antigens
 Patients with SLE may also develop autoantibodies
against adaptor molecules which facilitate phagocytosis
of apoptotic cells (C1q, MBL) resulting in defective
clearance, classical pathway complement activation, and
recruitment of inflammatory cells.
Defective clearance of apoptotic cells
 Delayed or defective apoptosis then allows for
prolonged exposure of intracellular antigens,
“inflammatory cell death phenotype,” inflammatory
cell recruitment and presentation of normally
protected intracellular components as antigens
allowing for autoantibody production
The importance of IFN-a
 IFN-a is able to activate APCs after uptake of self material as well as
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promote B cell differentiation into plasma cells
IFN-a levels appear to correlate with disease severity and levels of anti-DS
DNA in SLE
Patients with non-autoimmune diseases treated with IFN-a can develop
positive ANA, anti-DS DNA abs and occasionally SLE.
Conditions that naturally increase IFN-a levels (sunburn, viral infections)
can induce SLE flares.
IFN-a regulated genes are expressed at higher levels in the blood of SLE
patients
Plasmacytoid DCs are the major producers of IFN-a. SLE patients have
50-100 fold fewer in circulation as they have migrated to lymph tissues
where they remain activated
SNPs in interferon signaling related genes (Tyk2 and interferon regulatory
factor 5) also confer increased likelihood of developing lupus
SLE susceptibility polymorphism in STAT4 results in increased sensitivity
to IFN-a signaling.
The Innate Immune System May Also Play a Role
 Toll-Like Receptors recognize molecular patterns
(double stranded RNA, DNA, LPS etc) in order to
provide rapid response to invading pathogens. They
use defined signaling pathways to result in
production of inflammatory cytokines and initiate
inflammatory reactions.
 TLR7 and 9 are selectively expressed on PDCs
 Regulation in endosomes may regulate control of
NFkB vs. IRF7 activation in human plasmacytoid
dendritic cells
Signaling involving IRF7 or IRF 5 (polymorphisms in SLE) can lead to high levels of IFN-a production
http://www.sapphirebioscience.com/images/wallcharts/alexis_toll_like_receptors_detail.jpg
TLRs are thought to also recognize self antigens
in the context of inflammatory diseases
 All TLRs (except 5 and 10) have been shown to be activated by
endogenous molecules in the context of cell death
 TLR7 and 9 are expressed only in endosomes to decrease the
chance of coming in contact with endogenous RNA or DNA
 TLR7 and 9 are activated by DNA/anti-DNA IgG complexes
resulting in IFN-a and autoantibody production.
 However, immune complexes are taken up by cells with
FcgRIIa and taken to the endosome where they can activate
TLR 7 and 9. This Results in
signaling cascade activation that
increases production of IFN-a.
Image taken from Barrat and Coffman 2008
B-cell Disregulation
This contributes to the disregulation of the B-cell: increased levels of IFN-a differentiate
B-cells into antibody-producing plasmocytes and upregulates B-cell survival factors such
as BAFF.
Additionally, recent identification of a genetic linkage of an allele that suppresses B-lymphocyte
kinase levels in SLE emphasizes the importance of regulation of B cell proliferation and tolerance
Image taken from Barrat and Coffman 2008
Mechanism Summary
 Defects in clearance of apoptotic cells
can lead to exposure of intracellular
immunogenic components which can
be taken up by DC and presented to
autoreactive B cells (made this way
during random somatic hypermutation).
 In the right genetic environment, these
B cells may become activated to
produce autoantibodies.
 Polymorphisms or mutations in genes
in numerous steps of B-cell regulation or
IFN-a responsiveness can predispose to SLE (FcgRIIa, IRF5,
STAT4, BLK)
Mechanism Summary
 Once autoantibodies (particularly anti-DS DNA) are
present, they can complex with DNA exposed on
dying cells and then bind to the FcgRIIa on PDCs,
activate TLR 7 and 9, and result in high levels of
IFN-a production.
 IFN-a encourages a feed-forward mechanism of
continued plasma cell activation to produce
increased amounts of autoantibodies and encourage
further disease progression and tissue destruction.
Autoantibodies
 ANA: against targets in the nucleus, but only those which have intrinsic
immunological activity: i.e.. They can activate the innate immune system
via Toll-like receptors
 Anti DS-DNA in particular recognizes DNA in complex with nucleosome
components (histone-derived peptides in particular)
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Can correlate with nephritis
Immune complexes with anti-DNA ab/DNA can increase the expression of IFN-a via
plamacytoid dendritic cells
 Anti-Sm: detects ribonucleoproteins involved in processing of mRNA;
doesn’t track with disease, specific for lupus
 SSA/Ro and SSB/La: detect ribonucleoproteins, associated with SICCA
syndrome and photosensitivity
 Anti NMDA to subunits NR2a and NR2b may be associated with
neuropsychiatric symptoms
 “Antiphospholipid” antibodies are ab against phospholipid-binding
proteins or phospholipids that are prothrombogenic. Ex: lupus
anticoagulant, anticardiolipin, and anti beta2-glycoprotein I
Why are autoantibodies so bad?
 Renal disease
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IgA, IgM, IgG and complement deposition in the mesangium and
subendothelial and subepithelial of the GBM that results in
complement activation and recruitment of inflammatory cells that
result in tissue destruction.
Cross reactivity of anti-DS DNA antibodies with a-actinin may also
result in a direct focusing of complement activation
 Skin disease
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Inflammation and breakdown of the dermal-epidermal junction.
UV exposure can worsen because it promotes apoptosis in the skin
resulting in autoantibody binding and tissue injury via complement
activation or inflammatory cell activation
Anti-Ro antibodies are associated with skin flares
Why are autoantibodies so bad?
 In the CNS, vasculitis is rare
 Anti-NMDA receptor antibodies may contribute to cerebral
lupus phenotypes
 See more microinfarcts and degeneration or proliferative
changes in blood vessels, thought to be related to IC deposition
 Antiphospholipid abs may contribute to thrombotic
events anywhere in the body
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aPLs bind to endothelial cells, monocytes, neutrophils and
platelets causing inflammation and procoagulant release
This process is dependent on complement activation
How Understanding the Mechanism of SLE will
influence therapy
 Currently, general immunosuppressants and
antimalarials are the therapy of choice for lupus
(steroids, plaquenil) and lupus nephritis
(cyclophosphamide –cellcept may become an
approved option)
 Current therapies are limited by side effects
 No new FDA approved drug for lupus have surfaced
in 40 years!
 Research into the underlying mechanisms will allow
for more directed therapies that may provide better
control of SLE with fewer side effects
How Understanding the Mechanism of SLE will
influence therapy
 Removal of B cells may improve disease control
 Open label trials of rituximab (anti CD-20) have shown up to 80% response, 50%
with sustained response after 12 months. A recent RCT (EXPLORER) did not
show a benefit with rituximab but patients were very sick and both control and
study patients received high doses of steroids which may have undercut the
benefit seen in patients given rituximab
 Trials of anti-IFN-a antibodies are underway
 Preliminary trials of inhibitory DNA sequences to block immune
complex binding to TLRs suggest that preventing aberrant TLR 7
and 9 activation decreases IFN-a levels and disease flares
 Anti-IL-10 trials are ongoing. Preliminary trials suggest
improvement in skin and joint symptoms
 Trials are also ongoing to block other B-cell stimulating signals
(anti-BlyS=Belimumab, atacicept (soluble fusion protein that
inhibits Blys ligand) and to block helper T cell activation.
Summary
 Lupus is a disease of autoantibody formation that
results in varied clinical manifestations
 Disregulation of apoptosis, B-cell survival and
proliferation and IFN-a production appear to be the
major inciting events
 Ongoing research into the mechanisms which lead to
SLE will hopefully provide us with novel effective
therapies with improved side effect profiles
References
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Barrat, F.J. and R. Coffman., “Development of TLR inhibitors for the treatment of autoimmune diseases,” Immunological Reviews
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Frostegard, J., “Systemic Lupus Erythematosus and Cardiovascular Disease,” Lupus(2008) 17:364-367
Gaipl, U.S. et al., “Clearance of Apoptotic Cells in Human SLE.” Current Dir Autoimmun. (2006) 9: 173-187.
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Niiro, H. and Clark, E., “Regulation of B-cell fate by antigen-receptor signals” “Nature Reviews Immunology (2002) 2:945 – 956.
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www.emedicine.medscape.com
Kids!!!