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Module 204, Theme 1: Immunology > Autoimmune disease 1 > Flashcards

Autoimmune disease 1 Flashcards

1
Q

Autoimmunity

A

Immune responses to self-antigens, as a failure of tolerance.

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2
Q

Autoimmune disease

A

Adaptive immune response to self-antigens, causes damage to self-tissues.

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3
Q

Inflammatory disease

A

Immune system mediated response to host-tissues BUT does not involve the response of adaptive immune system to self-antigens.

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4
Q

Reasons for our susceptibility to autoimmunity.

A

Generation of T cells are random, so there will be inevitably be T cells that auto-reactive.
- Process of negative selection (to remove auto-reactive T cells) can be rigorous (increasing susceptibility to infections) or passive (increasing risk of autoimmunity).

Some of the inevitable auto-reactive T cells are released into circulation but should be regulated via peripheral tolerance mechanisms.
- When this fails= autoimmunity

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5
Q

Mechanisms of peripheral tolerance

A

Immunological hierarchy
- CD4 T cell will not be activated unless antigen is presented in an ‘inflammatory’ context with TLR ligation

Antigen segregation (immune privilege sites)

Peripheral anergy (no co-simulation or CD4L inhibition)

Treg cells

Cytokine deviation
- Change in T cell phenotype from Th1 to Th2

Clonal exhaustion

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6
Q

Pathogenic mechanism of Type 2 hypersensitivity diseases [5]

A

Antibody is pathogenic cause of disease/ tissue damage.

Criteria:

  • Disease can be transferred between experimental animals via serum.
  • Disease can be transferred via the placenta to the fetus during gestation.
  • Removal of antibodies via plasmapheresis is beneficial.
  • A pathogenic Ab can be identified and characterised.
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7
Q

Antibody-mediated autoimmune diseases examples

A

Autoimmune haemolysis

Autoimmune thrombocytopenia

Graves disease

Myasthenia gravis

Spontaneous urticaria

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8
Q

Autoimmune haemolysis

  • Mechanism
  • Presentation
A

Antibody-mediated autoimmune disease (T2 hypersensitivity)

  • Anti-RBC autoantibodies are generated and bind to RBCs
  • RBCs are recognised as pathogenic and are destroyed by phagocytes via phagocytosis or via activation of complement system.

Presents

  • Anaemia (conjunctival pallor)
  • Jaundice
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9
Q

Autoimmune thrombocytopenia

  • Mechanism
  • Presentation
A

Antibody-mediated autoimmune disease (T2 hypersensitivity)

Anti-platelet autoantibodies are generated.
- Destruction of platelets= increased bleeding

Presentation

  • Brusies
  • Purpura.
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10
Q

Graves disease

  • Mechanism
  • Presentation
A

Antibody-mediated autoimmune disease (T2 hypersensitivity)

B cells/ plasma cells generated autoantibodies to TSH receptors

  • Activates receptor, causing increased production of thyroid hormones
  • This is not regulated despite negative feedback reduction in TSH production- as stimulation of thyroid hormones is from Ab.

Presentation–> hyperthyroidism

  • Tachycardia, weight loss, arrthymia, tremors.
  • Graves opthalmopathy due to retro-orbital inflammation: proptosis, etc
  • Goitre
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11
Q

How Graves disease has all the characteristics of an antibody-mediated disease

A

Neonatal hyperthyroidism occurs in the fetus if the mother is affected.

Experiments have shown the disease to be transferred between animals through serum transfers.

The pathogenic antibody (TSH receptor Ab) can be detected and characterised.

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12
Q

Myasthenia gravis

  • Mechanism
  • Presentation
A

Antibody-mediated autoimmune disease (T2 hypersensitivity)

Autoantibodies are generated against ACh receptors

  • Blocks receptors
  • Leads to destruction of receptors, rendering synapses defective= no muscle contraction

Presentation

  • Primarily affects facial and eyelid muscle
  • Ptosis, worsens when asksed to blink repeatedly.
  • Muscle weakness and fatigability
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13
Q

Spontaneous urticaria

  • Mechanism
  • Presentation
A

Antibody-mediated autoimmune disease (T2 hypersensitivity)

Auto-IgG antibodies are generated for high affinity IgE mast cell receptors (Fce)
- IgG and FceR1 receptor binds and cross links–> granulation–> release of histamines

Presents:

  • Hives
  • Swelling
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14
Q

Type IV hypersensitivity diseases

A

Diseases where tissue damage is directly mediated by T cell-dependent mechanisms

  • Can activate macrophages + elements of the innate immune system
  • CD8 T cells damage tissue directly.

Experimental models relay on genetically susceptible animals that have been sensitised (exposure to self-antigen w/ adjuvant)

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15
Q

Autoimmune hypothyroidism

  • Mechanism
  • Presentation
A

T cell-mediated autoimmunity (Type IV hypersensitivity disease)

Thyroid is infiltrated by CD4 and CD8 T cells
- Leads to autoimmune destruction of Thyroid tissue

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16
Q

Coeliac disease

  • Mechanism
  • Presentation
A

IBD

Exogenous gluten is recognised as antigenic and broken down into gliadin peptides using transglutamine 2
- HLA DQ2/8 can present there peptides to T cells if they are expressed–> Ab produced do not contribute to tissue damage BUT CD8 T cells attack epithelial cells.

17
Q

DiGeorge syndrome

  • Genetics
  • Full phenotype
  • Presentation
A

Microdeletion in chromosome 22= failure of 3/4 brachial arches to migrate

Full phenotype

  • No parathyroid
  • Cleft palate
  • Congenital heart defect
  • Thymic aplasia

Presentation

  • Very variable due to the incomplete penetrance of the genes.
  • Immunodeficiency is a spectrum (from mild to SCID-like)
  • Common autoimmunity
18
Q

APACED

A

Autoimmune polyglandular syndrome, candidiasis and ectodermal dystrophy.
- Monogenic autoimmunity disorder

AIRE gene (expresses ectopic tissue-specific antigens) mutation
- Failure of negative selection--> auto-reactive T cells released into circulation

Diseases asscoiated

  • T1 DM
  • Vitiligo
  • Alopecia
  • Autoimmune adrenal disease

Candidiasis
- Occurs from autoantibodies against IL-17= increased fungal infections at mucosal surfaces

19
Q

Deficiency of C1q/ C2/ C4

A

Predisposes to lupus

  • Inability to clear immune complexes
  • Recurrent bacterial infections

Cannot produce C3b, involved in removing immune complexes

20
Q

IPEX

  • Genetics
  • Presentation
A

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked

Mutation of FoxP3 gene
- Inhibits the production of CD4, CD25 and FoxP3 T reg cells.

Presentation

  • IBD
  • Dermatitis
  • Organ specific autoimmunity

Module 204, Theme 1: Immunology (22 decks)

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