Immunology

Question 1

1 Define hypersensitivity

Answer 1

“the antigen-specific immune responses that are either inappropriate or excessive AND result in harm to host”

Question 2

1. List and describe the 4 types of hypersensitivity reactions

Answer 2

Type I -immediate (Allergy)
Type II - antiBody mediated
Type III - immune Complex mediated
Type Iv - cell mediated Delayed

Question 3

1. What are the 2 typical phases of a hypersensitivity reaction?

Answer 3

Sensitisation phase (activation of APCs and memory effector cells 
Effector phase (reexposure -> activation of memory cells)

Question 4

1. Over what time frame would a type II hypersensitivity reaction present over?

Answer 4

5-12 hours

Question 5

1. Which types of antibodies are usually involved in a type II hypersensitivity reaction?

Answer 5

IgG or IgM

Question 6

1. What causes tissue/cell damage in type II hypersensitivity?

Answer 6

Complement system (MAC,
C3a and b, C5a)
Antibody dependant cell cytotoxicity

Question 7

1. Give 2 examples of hypersensitivity reactions where the affected antigen is a receptor

Answer 7

Grave's disease (TSH receptor)
Myasthenia gravis (Acetylcholine receptor)

Question 8

1. What 4 approaches are used to combat cell/tissue damage in type II hypersensitivity?

Answer 8

Immune suppression (reverse complement activation)
Plasmapheresis (remove circ. antibodies and inflamm mediators)
Splenectomy (reduce opsonisation/phagocytosis)
IV immunoglobulin (replaced degraded IgG)

Question 9

1. What type of immune reaction is haemolytic disease of the newborn?

Answer 9

Type II hypersensitivity reaction (of a Rhesus negative mother against Rhesus antigen on foetal blood cells )

Question 10

1. How does type III hypersensitivity cause tissue damage?

Answer 10

Intermediate size immune complex deposition -> complement activation -> neutrophil chemotaxis, adherence and degranulation

Question 11

1. What is the most prevalent disease caused by type III hypersensitivity?

Answer 11

Systemic Lupus Erythematosus

Question 12

1. How does lupus typically present?

Answer 12

Women (9:1 F:M)
Every presentation unique but ..
may have repeated miscarriages, many have cardiac, resp, renal, joint and neuro features; most commonly:
low grade fever
photosensitivity
mouth ulcers
arthritis
pericarditis
pleuritis
fatigue
anorexia
butterfly malar rash
poor peripheral circulati

Question 13

1. Which inflammatory cells are typically involved in type IV hypersensitivity?

Answer 13

Lymphocytes

Macrophages

Question 14

1. What are the three main subtypes of type IV hypersensitivity?

Answer 14

Contact hypersensitivity,
Tuberculin hypersensitivity
Granulomatous hypersensitivity

Question 15

1. Over what time frame does type IV hypersensitivity typically present?

Answer 15

Usually develops within 24 to 72 hours

Question 16

1. In tuberculin hypersensitivity, in which tissue does the reaction take place?

Answer 16

In the dermis of the skin

Question 17

1. In type IV hypersensitivity, how are resting macrophages activated?

Answer 17

By interferon gamma and tumour necrosis factor beta produced by TH1 lymphocyte

Question 18

1. List four diseases which are associated with granuloma formation

Answer 18

Tuberculosis
Tuberculoid leprosy
Schistosomiasis
Sarcoidosis

Question 19

1. Name 2 tests that utilise the tuberculin hypersensitivity

Answer 19

Mantoux test (TB)
Lepromin test (leprosy)

Question 20

1. Which three common autoimmune diseases are caused by type IV hypersensitivity?

Answer 20

Insulin-dependent diabetes mellitus
Hashimoto’s thyroiditis CD8 + T cells and antibodies)
Rheumatoid arthritis (IgG)

Question 21

1. What 4 specific treatments are currently available for type III and IV hypersensitivity?

Answer 21

Monoclonal antibodies:
B and T cells
cytokine network
antigen-presenting cells

Anti-TNF (for rheumatoid arthritis)

Question 22

1. Name three drugs are used as steroid sparing agents.

Answer 22

azathioprine
mycophenolate mofetil
cyclophosphamide

Question 23

1. Over what time frame do type I hypersensitivity reactions typically present?

Answer 23

Immediately - less than 30 minutes

Question 24

1. What are two main mechanisms underlying the pathology of allergy?

Answer 24

Abnormal adaptive immune response (Th2 response and IgE production)
Mast cell activation

Question 25

1. Explain the biodiversity hypothesis of the pathogenesis of allergy

Answer 25

Compositional and functional alterations of micro-biome (dysbiosis) due to Western lifestyle (medicalised birth, antibiotics, processed food, sanitised environments) is thought to target immune system towards Th2 response

Question 26

1. What does evidence supporting the hygiene hypothesis suggested about the pathogenesis of allergy?

Answer 26

Children exposed animals, pets and microbes in the early postnatal period appear to be protected against certain allergic diseases (hayfever, eczema, asthma)

Question 27

Year one: in what tissues would you find mast cells?

Answer 27

Most mucosal and epithelial tissues i.e. GI tract, skin, respiratory epithelium
mIn connective tissue surrounding blood cells

Question 28

1. What are the six main mast cell mediators implicated in allergy?

Answer 28

tryptase
histamine
platelet activating factor
leukotrienes C4, D4 and D4

Question 29

1. What is the cellular mechanism behind the formation of allergic urticaria?

Answer 29

Mast cell activation within epidermis, leading to release of histamine and leukotrienes / cytokines (mediators) resulting in increased vascular permeability and vasodilation thus redness and swelling.

Question 30

1. What are the 6 main possible signs of anaphalaxis?

Answer 30

Difficulty breathing (due to bronchial constriction)
Hypotension
Cardiovascular collapse
Generalised urticaria
Angioedema
Abdo pain, nausea and vomiting

Question 31

1. What treatment options are available for severe allergies?

Answer 31

Allergen desensitisation / oral immunotherapy
Anti-IgE monoclonal antibodies
Anti-histamines
Corticosteroids
Leukotriene receptor antagonists (eg Montelukast)