IMMUNO: Autoimmune and Autoinflammatory Disease Flashcards
What is immunopathology? Give some examples.
Damage to host caused by the immune response
In the context of immunopathology, what is auto-inflammatory or auto-immune disease? What are the types?
Immunopathology in the absence of infection
Innate immune response cause = auto-inflammatory
Mixed innate adaptve = mixed
Adaptive immuno response cause = auto-immune
What is the cause of auto-inflammatory disease?
Local factors at sites predisposed to disease lead to activation of innate immune cells such as macrophages and neutrophils, with resulting tissue damage
What is the cause of auto-immune diseases?
Aberrant T cell and B cell responses in primary and secondary lymphoid organs lead to breaking of tolerance with development of immune reactivity towards self-antigens
Organ-specific antibodies may predate clinical disease by years
Adaptive immune response plays the predominant role in clinical expression of disease
How do genetics influence the formation of auto-inflammatory/immune disease? Which are most common?
Polygenic or monogenic (mixed disease is only polygenic, others can be both)
Polygenic is most common
What type of genetic changes, apart from just inherited DNA, can cause these conditions?
- Germline mutations affecting DNA sequence - Alteration in DNA that occurs in germ cells (sperm and ova and progenitors) and will be passed on to offspring
- Somatic mutations affecting DNA sequence - Alteration in DNA that occurs in a single body cell after conception, does not affect germ cells and so is not inherited
- Epigenetics - (Heritable) change in gene expression (eg via DNA methylation)
- MicroRNA (miRNA) - Small, non-coding, single stranded RNA targets mRNA and regulate protein production
Give 2 examples of rare monigenic auto-inflammatory diseases.
Familial Mediterranean fever
TRAPS
How do monogenic auto-inflammatory conditions classically present?
Classically present with
- periodic fevers
- skin/joint/serosal/CNS etc inflammation
- high CRP
What is the cause of monogenic auto-inflammatory conditions? Which cytokines are most involved?
Mutations in a gene encoding a protein involved in a pathway associated with innate immune cell function
Abnormal signalling via key cytokine pathways involving TNF-alpha and/or IL-1 is common
What is the pathophysiology of familial mediterranean fever?
- Autosomal recessive condition
- Mutation in MEFV gene
- MEFV gene encodes pyrin-marenostrin
- Pyrin-marenostrin expressed mainly in neutrophils (negative regulator for inflammation)
- Failure to regulate cryopyrin driven activation of neutrophils
What is the clinical presentation of familal mediterranean fever?
Periodic fevers lasting 48-96 hours associated with:
- Abdominal pain due to peritonitis
- Chest pain due to pleurisy and pericarditis
- Arthritis
- Rash
Usually in people of Mediterranean origin.
What are the complications of FMF?
Complication - AA amyloidosis
Liver produces serum amyloid A as acute phase protein
Serum amyloid A deposits in kidneys, liver, spleen
Deposition in kidney often most clinically important
- Proteinuria - nephrotic syndrome
- Renal failure
What investigations are done to diagnose FMF?
- High CRP, high SAA
- Blood sample to specialist genetics laboratory to identify MEFV mutation
What is the treatment for FMF?
- Colchicine 500ug bd (1st)- binds to tubulin in neutrophils and disrupts neutrophil functions including migration and chemokine secretion
- IL-1 blocker (anakinra, canukinumab) - 2nd
- TNF alpha blocker
Give 3 examples of Rare Monogenic Auto-immune Diseases.
- APS-1, APECED
- ALPS
- IPEX
What are the main abnormalities in IPEX and ALPS?
Mutation in a gene encoding a protein involved in a pathway associated with adaptive immune cell function
- Abnormality of regulatory T cells - IPEX
- Abnormality of lymphocyte apoptosis - ALPS
What does IPEX stand for? What is the pathophysiology?
Immune dysregulation, polyendocrinopathy, enteropathy, X- linked syndrome = IPEX
Mutations in Foxp3 (Forkhead box p3) which is required for development of Treg cells
Failure to negatively regulate T cell responses –>
- Autoreactive B cells
- limited repertoire of autoreactive B cells
What are the clinical complications of IPEX?
Autoimmune diseases –>
- Diabetes Mellitus
- Hypothyroidism
- Enteropathy
- ‘Diarrhoea, diabetes and dermatitis’
What does ALPS stand for? What is the pathophysiology?
Auto-immune lymphoproliferative syndrome = ALPS
Mutations within FAS pathway
- Eg mutations in TNFRSF6 which encodes FAS
- Disease is heterogeneous depending on the mutation
Defect in apoptosis of lymphocytes –>
- Failure of tolerance
- Failure of lymphocyte ‘homeostasis’
High lymphocyte numbers with large spleen and lymph nodes
What is seen clinically in ALPS?
- High lymphocyte numbers with large spleen and lymph nodes
- Auto-immune disease - commonly auto-immune cytopenias
- Lymphoma
Give 3 examples of Polygenic Auto-inflammatory Diseases.
- Crohns disease
- Ulcerative colitis
- Osteoarthritis
- Giant cell arteritis
- Takayasu’s arteritis
How important is HLA association in Polygenic Auto-inflammatory Diseases? Are auto-antibodies present?
- Not a strong association in HLA
- In general these disease are not characterised by presence of auto-antibodies
What are the genetics of IBD in general? Is FH important? What about dizygotic twins?
Polymorphisms, >200 loci identified
Familial association studies and twin studies suggested genetic predisposition to disease
- 15% patients have an affected family member
- 50% vs <10% disease concordance in monozygotic vs dizygotic twins
*
Which mutations are important in Crohn’s disease?
IBD1 gene = NOD2 gene mutation
- IBD1 gene on chromosome 16 identified as NOD2 (CARD-15, caspase activating recruitment domain -15).
- Three different mutations of this gene have each been shown to be associated with Crohn’s disease.
- NOD2 gene mutations are present in 30% patients (ie not necessary)
- Abnormal allele of NOD2 increases risk of Crohn’s disease by 1.5-3x if one copy and 14-44x if two copies (ie not sufficient)
- Mutations also found in patients with Blau syndrome and some forms of sarcoidosis
How does NOD2 mutation cause Crohn’s?
-
NOD2 expressed in cytoplasm of myeloid cells – macrophages, neutrophils, dendritic cells
- NOD2 is a cytoplasmic microbial sensor which recognises muramyl dipeptide on bacterial products–> stimulates NFK-beta (–> TNFa)
- Activation induces autophagy in dendritic cells
What are the clinical features of Crohn’s disease? What is the treatment?
Clinical features
- Abdominal pain and tenderness
- Diarrhoea (blood, pus, mucous)
- Fevers, malaise
Treatment may include
- Corticosteroid
- Anti-TNF alpha antibody
Which factors can affect the following in Crohn’s?
- Expression of pro-inflammatory cytokines/chemokines
- Leukocyte recruitment
- Release of proteases, free radicals
Give 3 examples of mixed pattern diseases.
- Axial spondyloarthritis
- Psoriatic arthritis
- Behcet’s syndrome
Is there HLA association and presence of autoantibodies in mixed pattern disease? What are the genetics?
HLA associations may be present
Auto-antibodies are not usually a feature
Mutations affect pathways in adaptive and innate immune pathways
What role do genetics play in ankylosing spondylitis?
Highly heritable - 90% of the risk of developing disease is genetic
HLAB27, IL23R and ILR2 are invovled
What sites are most affected in ankylosing spondylitis?
- Enhanced inflammation occurs at specific sites where there are high tensile forces
- (entheses - sites of insertions of ligaments or tendons)
What is the presentation of ankylosing spondylitis? What is the treatment?
Presentation
- Low back pain and stiffness
- Enthesitis
- Large joint arthritis
Treatment
- Non-steroidal anti-inflammatory drugs
- Immunosuppression
- Anti-TNF alpha
- Anti-IL17
FMF
IPEX
Crohn’s
Give 5 examples of Polygenic Auto-immune Diseases.
Rheumatoid arthritis
Systemic lupus erythematosus
Myaesthenia Gravis
Primary biliary cholangitis
Pernicious anaemia
Addison disease
Are there autoantibodies/HLA associations in polygenic autoimmune diseases? What are the genetics?
HLA associations are common
Aberrant B cell and T cell responses in primary and secondary lymphoid organs lead to breaking of tolerance with development of immune reactivity towards self-antigens
Auto-antibodies are found
Mutations affect pathways in the adaptive immune response
Name some polymorphisms causing T cell actication in polygenic auto-immune disease.
How does HLA association relate to polygenic autoimmune disease? How does HLA association correspond to risk?
HLA presentation of antigen is required for development of T cell and T cell-dependent B cell responses
How did Gel and Coombs classify effector mechanisms of immunopathology?
Gel and Coombs (1960s) classified skin test ‘hypersensitivity’ reactions according to the type of immune response observed
Effector mechanisms for immunopathology
What is the Gel and Coombs classification for polygenic auto-immune disease?
-
Type I: Anaphylactic hypersensitivity
- Immediate hypersensitivity which is IgE mediated – rarely self antigen
-
Type II: Cytotoxic hypersensitivity
- Antibody reacts with cellular antigen
-
Type III: Immune complex hypersensitivity
- Antibody reacts with soluble antigen to form an immune complex
-
Type IV: Delayed type hypersensitivity
- T-cell mediated response
Which type of reaction is antibody-driven according to Gel and Coombs?
Type II
Antibody (autoantibody) binds to cell associated antigen e.g. cell or matrix-associated antigen
Give 3 examples of type II driven auto-immune disease.
- Goodpasture disease - against non-collagenous domain of BM collagen type IV
- Pemphigus vulgaris - against epidermal cadherin
- Graves disease - against TSHR
- MG - against AChR
Give the 2 types of immunopathogenic mechanisms present in type II disease.
-
Antibody dependent destruction (NK cells, phagocytes, complement)
- Complement activation –> cell lysis
- Ig Fc R interaction with NK cells –> release of cytolytic granules and membrane attack
- Phagocyte –> phagocytosis
- Receptor activation or blockade (sometimes considered type V response)
Which types of reactions are immune complex driven in autoimmune disease?
Type III - antibody binds to soluble antigen to form cicrulating immune complex
What are the mechanisms of T3 disease?
- Antibodies bind to soluble antigen to form circulating immune complex
- Immune complexes deposit in blood vessels
- Complement activation, infiltration of macrophages and neutrophil
- Cytokine and chemokine expression
- Granule release from neutrophils
- Increased vascular permeability
- Inflammation and damage to vessels
- Cutaneous vasculitis
- Glomerulonephritis
- Arthritis
Give an example of type III complex driven autoimmune disease.
Which delayed-type hypersensitivity reaction in autoimmunity is mediated by T cells? What are the 2 mechanisms?
Tissue destruction by…
- HLA class 1 present SELF-antigens to CD8 T cells → cell lysis
- HLA class 2 present SELF-antigen to CD4 T cells → cytokine production → inflammation and tissue damage
Give an example of type IV T-cell mediated disease.
Insulin dependent DM - autoantigen is the pancreatic beta-cell antigen
How are polygenic autoimmune diseases classified?
Organ specific diseases vs multisystem diseases
Is measuring anti-thyroglobulin and anti-thyroid peroxidase antibodies clinically useful?
High prevalence so no - do TFTs
In terms of the classification (types 1-4) what effects mechanisms is present in T1DM?
CD8 T-cell mediated type IV pathology – recognise autoantigens presented by
MHC Class I molecules on beta cells
Where are these autoantibodies present?
- Graves disease (hyperthyroidism)
- Hashimoto disease
- Hashimoto disease
What is the cause?
- Tired
- Pale
- Mild numbness of feet
- Anaemic Hb 8.4
- Macrocytosis MCV 108
- Urine dipstick –ve
- Folate normal
- Vitamin B12 very low
Pernicious Anaemia
Where are these autoantibodies present?
- Pernicious anaemia
- Pernicious anaemia
- Coeliac
- Coeliac
- Ulcerative colitis>Crohns
Where are these autoantibodies present?
- Autoimmune hepatitis, Primary biliary cholangitis
- Autoimmune hepatitis
- Autoimmune hepatitis
- Primary biliary cholangitis
- Autoimmune hepatitis, Primary biliary cholangitis
Myaesthenia gravis
Where are these autoantibodies present in terms of neurological disease?
- Myaesthenia Gravis
- Myaesthenia Gravis with myositis
- Neuromyelitis optica spectrum disorder (NMOS)
- Optic neuritis, encephalomyelitis
- Encephalitis (may be malignancy associated)
- Seizures (may be malignancy associated)
How are antibodies in Goodpasture syndrome detected? What do they show? What is seen on biopsy?
Fluorescein conjugated polyclonal anti-human immunoglobulin viewed under UV source and fluorescence microscope
Antibodies may be detected in tissue sections. –> shows smooth linear deposition of antibody along the glomerular basement membrane
Crescentic nephritis is seen on biopsy
Which renal diseases are these present in?
- Goodpasture disease
- ANCA associated vasculitis - Microscopic polyangiitis / Eosinophilic granulomatosis with polyangiitis
- ANCA associated vasculitis - Granulomatosis with polyangiitis
What is the diagnosis?
- Pain, stiffness and swelling of multiple small joints within hands
- Normochromic anaemia
- High ESR and CRP
RhA
What is rheumatoid factor? What type of Ig is this? How useful is it for diagnosis?
A rheumatoid factor is an antibody directed against the common (Fc) region of human IgG
IgM anti-IgG antibody is most commonly tested although IgA and IgG rheumatoid factors may also be present in some individuals
Around 60-70% specificity and sensitivity for diagnosis of rheumatoid arthritis
Menti: Which of the following is an example of Gel and Coombs type III hypersensitivity:
- Goodpasture disease
- Eczema
- SLE
- Multiple sclerosis
- Graves disease
Anti AChR
How do we detect anti-nuclear antibodies? What do they bind? How common are they?
Group of antibodies that bind to nuclear proteins
Test by staining of Hep-2 cells (human epidermoid cancer line) and Fluorescein conjugated polyclonal anti-human immunoglobulin
Very common - Low titre antibodies (<1:80) often found in normal individuals (esp older women)
What is the diagnosis?
- 19yo with 4 month history of fatigue
- Generalised arthralgia, particularly of small joints of hands
- Hair fall
- Mouth ulcers
- Butterfly rash
SLE
Compare/contrast these images of renal pathology in SLE and Goodpasture’s disease.
Lupus nephritis = Immune complex deposition, detection of granular ‘lumpy-bumpy’pattern with fluorescein conjugated anti-human Immunoglobulin used; type III hypersensitivity
Goodpasture’s syndrome = Smooth linear deposition of antibody along the glomerular basement membrane; Type II hypersensitivity; fluorescein conjugated polyclonal anti-human Ig used
What are the targets of ANA (anti-nuclear antibody) in general?
- dsDNA
- Ro, LA, Sm, U1RNP ribonucleoproteins
- SCL70 topoisomerase
- Centromere
Therefore a positive ANA will trigger the laboratory to investigate for dsDNA and ENA antibodies.
What is shown in this SLE investigation?
ANA Pattern
- Homogeneous staining associated with specificity for dsDNA
- Specificity investigated with ELISA based assay
What test for SLE is shown by this image? What does this mean? What is a follow up test for this result?
Speckled antibodies shown which are often associated with antibodies to extractable nuclear antigens;
Could suggest presence of some ribonucleoproteins (Ro, La, Sm, U1RNP) – but needs to be confirmed with ELISA
What are complement levels usually like in SLE? Is measurement of C3/4 a useful marker in SLE?
Formation of antibody-antigen immune complexes –> activate complement cascade via classical pathway –> complement components become depleted if constantly consumed
Quantitation of C3 and C4 acts as a surrogate marker of disease activity
- C4 may be low in active disease
- C3 and C4 will be low in severe active disease
[NB we measure UNACTIVATED complement proteins, not activated forms]
What is the diagnosis?
Systemic sclerosis
Which types is diffuse vs limited systemic sclerosis in these ANA stains?
- Limited cutaneous systemic sclerosis -
- anti-centromere antibodies
- Diffuse cutaneous systemic sclerosis
- nucleolar pattern
- anti-topoisomerase antibodies (Scl70)
- RNA polymerase
- Fibrillarin
Mutually exclusive, highly specific
What is the diagnosis?
- Weakness
- Malaise
- Rash
Idiopathic inflammatory myopathy - dermatomyositis + polymyositis
What type of staining is shown in this investigation for idiopathic inflammatory myopathy?
Cytoplasmic anti-Jo1 staining - this is a type of anti-aminoacyl tRNA synthetase antibody
Which rheumatological conditions are these autoantibodies found in ?
- Rheumatoid arthritis
- Rheumatoid arthritis + Primary Sjogrens
- Connective tissue disease (screening)
- Systemic lupus erythematosus
- Systemic lupus erythematosus
- Systemic lupus erythematosus or mixed connective tissue disease
Which rheumatological conditions are these autoantibodies found in ?
- Systemic lupus erythematosus or mixed connective tissue disease
- Primary Sjogren’s or SLE
- Limited cutaneous systemic sclerosis
- Diffuse cutaneous systemic sclerosis
- Idiopathic inflammatory myositis
- Anti-phospholipid syndrome
What is the diagnosis?
Patient 54 year old woman is referred with recurrent nose bleeds and breathlessness
Systemic vasculitis - small vessel (ANCA associated) e.g microscopic polyangitis, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis.
How are systemic vasculitidies classified?
What are the diffferences between these ANCA stains?
- Cytoplasmic fluorescence - antibodies to enzyme proteinase 3
- Perinuclear staining pattern - antibodies to myeloperoxidase
Compare and contrast cANCA and pANCA. Which is associated with MPA, GPA and eGPA?
cANCA
- Cytoplasmic fluorescence
- Associated with antibodies to enzyme proteinase 3
- Occurs in > 90% of patients with granulomatous polyangiitis (GPA) with renal involvement
p-ANCA
- Perinuclear staining pattern
- Associated with antibodies to myeloperoxidase
- Less sensitive and specific than cANCA
- Associated with microscopic polyangiitis (MPA) and eosinophilic granulomatous polyangiitis (eGPA)
SLE - dsDNA antibodies are quite specific
ANCA-associated vasculitis
