Pathogenesis of Autoimmune Disease Flashcards

1
Q

Define Rheumatoid Arthritis.

A

Chronic autoimmune disease characterised by pain, stiffness and symmetrical synovitis of synovial joints

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2
Q

What is the site of inflammation in rheumatoid arthritis?

A

Synovium

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3
Q

What are the two main autoantibodies that are associated with rheumatoid arthritis?

A

Rheumatoid factor

Anti-cyclic citrullinated peptide antibody

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4
Q

Other than at joints, where else is synovium found?

A

Around tendons (tenosynovium)

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5
Q

Define Ankylosing Spondylitis.

A

Chronic spinal inflammation that can result in fusion and deformity

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6
Q

What is the site of inflammation in ankylosing spondylitis?

A

Entheses – where a ligament or a tendon inserts into bone

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7
Q

What family of diseases is ankylosing spondylitis a part of?

A

Seronegative spondyloarthropathies

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8
Q

Which other diseases fall into the same family of diseases as Ankylosing spondylitis?

A

Reiter’s syndrome and reactive arthritis
Psoriatic arthritis
Enteropathic synovitis

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9
Q

Define Systemic Lupus Erythematosus (SLE).

A

Chronic tissue inflammation in the presence of antibodies directed at self-antigens
NOTE: it is inflammation of sterile tissue

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10
Q

Lupus causes multi-site inflammation but state some sites that are particularly badly affected.

A

Joints, Skin and Kidneys

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11
Q

What are the two autoantibodies that are associated with lupus?

A

Anti-nuclear antibodies

Anti-double stranded DNA antibodies

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12
Q

What family of diseases is lupus a part of?

A

Connective tissue diseases

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13
Q

What other diseases are part of the same family as lupus?

A

Systemic sclerosis (diffuse and localised)
Polymyositis/Dermatomyositis
Sjogren’s syndrome
Mixed connective tissue disease

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14
Q

What is Sjogren’s syndrome?

A

An autoimmune disease that targets the exocrine glands (e.g. lacrimal glands)

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15
Q

What are the MHC associations of rheumatoid arthritis, ankylosing spondylitis and SLE?

A

Rheumatoid arthritis = HLA-DR4
SLE = HLA-DR3
Ankylosing spondylitis = HLA-B27

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16
Q

On which chromosome is HLA encoded?

A

Chromosome 6

17
Q

A change in which class of MHC is associated with rheumatoid arthritis, ankylosing spondylitis and SLE?

A

Ankylosing spondylitis = Class 1

Rheumatoid Arthritis + SLE = Class 2

18
Q

Which cells express class I MHC and which cells recognise this class of MHC?

A

All nucleated cells (they display endogenous antigens)

They are recognised by CD8+ T cells

19
Q

Which cells express class II MHC and which cells recognise this class of MHC?

A

Antigen presenting cells e.g. macrophages, dendritic cells (they display exogenous antigens)
Recognised by CD4+ T cells

20
Q

How does HLA-B27 cause ankylosing spondylitis?

A

Ankylosing spondylitis is independent of CD8+ T cells

HLA-B27 has a propensity to misfold, which causes cellular stress and triggers the release of IL-23 and IL-17 by adaptive immune cells and innate immune cells

The release of chemical mediators leads to inflammation

The cellular stress is most likely to occur in innate immune cells and these are present in the entheses – hence why ankylosing spondylitis causes enthesitis

21
Q

What is the difference in the specificity of the autoantibodies in SLE?

A

Anti-nuclear antibodies are found in all cases of SLE but isn’t specific to SLE

Anti-dsDNA antibodies are specific to SLE – serum level of this antibody correlates with disease activity

22
Q

How is the presence of anti-nuclear antibodies detected?

A

Some cells are permeabilised so the antibodies can enter the cell andthen the patient’s serum is washed over the cells
If there are anti-nuclear antibodies, they will bind to the nuclearantigens

23
Q

What are the features of a sick lupus patient in terms of complement levels and serum levels of anti-dsDNA antibodies?

A

Low complement levels - complement is activated by immune complexes so gets used up.

High serum levels of anti-dsDNA antibodies

24
Q

How do antinuclear antibodies react with nuclear antigens, which are found within the nucleus?

A

Apoptosis leads to the translocation of nuclear antigens onto the surface of the cell so that they are accessible to the immune system

In lupus, apoptotic cells are not cleared normally

This impaired clearance enables abnormal presentation to the immune system

The immune response is amplified through B cells

25
Q

State some important cytokines in rheumatology.

A

IL-1 – produced by macrophages and activates T cells, fever + pro-inflammatory

IL-2 – produced by T cells – activates T + B cells

IL-6 – produced by T cells – activates B cells + acute phase response

TNF-alpha – produced by macrophages – similar to IL-1 but more destructive

Gamma-IFN – produced by T cells – activates macrophages

26
Q

Blockage of which cytokine with biological therapy has proven to be very effective in reducing some of the negative effects of rheumatoid arthritis?

A

TNF-alpha

Potential for IL-6

27
Q

Other than cytokine blockade, what else can be targeted to improve symptoms in rheumatoid arthritis?

A

B cell depletion (B cell hyperactivity is a key feature of SLE)

28
Q

What is RANKL produced by in rheumatoid arthritis and what does it do?

A

RANKL is produced by T cells and synovial fibroblasts

It stimulates osteoclast formation

Physiologically produced by pre-osteoblasts

29
Q

What can upregulate RANKL production?

A

IL-17 -> potent action on osteoclastogenesis

IL-1

TNF-alpha

PTH-related peptide

30
Q

What decoy receptor antagonises the action of RANKL?

A

Osteoprotegrin

31
Q

Name a monoclonal antibody that targets RANKL.

A

Denusomab

32
Q

State two drugs that deplete B cells and specify what they target.

A

Rituximab – anti-CD20 monoclonal antibody

Belimumab – anti-BLYS monoclonal antibody (BLYS is a B cell survival factor, BLYS aka BAFF)

33
Q

What are the effects of prostaglandins produced by COX?

A

Vasodilation (PGI2)

inhibit platelet aggregation (PGI2)

bronchodilation (PGE2, PGI2)

uterine contraction (PGF2alpha)

34
Q

What are the effects of leukotrienes produced by lipooxygenase?

A

Leukocyte chemotaxis

smooth muscle contraction

bronchoconstriction

mucous secretion

35
Q

What do glucocorticoids inhibit?

A

Phospholipase A2

36
Q

What causes the damage in lupus?

A

Immune complexes travel in the circulation to lots of sites in the body e.g. cause damage in the kidney glomeruli