Hypersensitivity

Question 1

What is hypersensitivity? (1)

Answer 1

Harmful over reaction to non-self innocuous antigens

Question 2

What is type 1 hypersensitivity? (3)

Answer 2

Atopic diseases caused by individual tendency to mount over zealous IgE responses
IgE-mediated degranulation of mast cells
Degranulation has various effects - increase in mucus production, vascular leakage etc
Immediate (within 30 mins)

Question 3

What is type 2 hypersensitivity? (3)

Answer 3

Cytotoxic reaction (complement lysis/ADCC)
e.g. drug allergy
IgG/IgM mediated
Takes days

Question 4

What is type 3 hypersensitivity? (3)

Answer 4

Immune complex reaction (complement activation)
IGg mediated
e.g. allergic vasculitis
6-8 hours

Question 5

What is type 4 hypersensitivity? (3)

Answer 5

T-cell mediated, delayed type hypersensitivity
e.g. allergic contact eczema
48-72 hours

Question 6

Organ manifestation of type I-allergic diseases (4)

Answer 6

Skin mucosa - 45%
Respiratory tract - 25%
Gastrointestinal tract - 20%
Cardiovascular system - 10%

Question 7

How is type 1 hypersensitivity diagnosed (2)

Answer 7

Skin prick test - inject small amounts of allergens into skin and wait for histamine mediated response
In vitro - ELISA used to look for levels of IgE in the blood

Question 8

Why are allergies on the increase? (2)

Answer 8

Hygiene hypothesis - exposed to less harmful pathogens, change to a clean environment in developed countries skews the immune response to a Th2 response

Counter regulation hypothesis - do not produce T regulatory cells due to living in a clean environment

Question 9

Which hypothesis is more accurate: hygiene hypothesis or counter regulation? (1)

Answer 9

Counter regualtion

Question 10

What are the causes of type 1 hypersensitivity? (2)

Answer 10

Genetic susceptibility
Environment

Question 11

What are the genetic factors responsible for type 1 hypersensitivity? (4)

Answer 11

Genes triggering the immune response or directing CD4 TH cell differentiation
Genes regulating TH2 cell differentiation and effector afunction
Genes expressed in epithelial cells
Genes identified by positional cloning

Question 12

What is affected by allergic Rhinitis and what are the symptoms? (5)

Answer 12

Mediated by antihistamines
Upper airways
- Nasal itch
- Sneeze
- Rhinorhoea
- Nasal obstruction

Question 13

What is affected by asthma and what are the symptoms? (6)

Answer 13

Lower airways
- Bronchoconstriction
- Mucus hypersecretion
- Wheeze
- Breathlessness
- Cough

Question 14

How to prove if it is a TH2 driven disease? (3)

Answer 14

Animal experiment - remove a gene and generate a knockout mice
Remove transcript factor for a particular T helper cell (TH1) - T bet 1
Produce more TH2 response
Leads to tissue remodelling - fibrosis

Question 15

What is Anaphylaxis? (4)

Answer 15

Direct allergen injected into circulation
Activate mast cells and cause vascular leakage
Catastrophic lowering of blood pressure, airway constriction, swelling of epiglottis

Question 16

What can be used to treat anaphylaxis? (1)

Answer 16

Epinephrine relaxes bronchiole smooth muscle

Question 17

What are eosinophils? (2)

Answer 17

Normally kill parasites via reacting towards opsonised parasites

However large amounts of IL5/Il3 in allergy cause degranulation

Question 18

Non-IgE allergic diseases-Type III (5)

Answer 18

Antibodies floating around
Antigen/allergen binds to it
Complement fixation
Produce C5a - anaphylatoxin
Cause degranulation of mast cells and recruitment of macrophage and neutrophils

Question 19

Coeliac disease (3)

Answer 19

Microvilli destroyed
Lymphoid cells - important for reacting quickly against antigens - activated by dendritic cells
dendrite cells present antigen
T cells become activated and destroy mucosal surface

Question 20

How does cellular destruction occur in coeliac disease? (4)

Answer 20

Peptides produced by gluten protein
Dendritic cell present on MHC class two cell
T cell activated and cause damage to mucosal layer by apoptotic ligands
ligands interact with mucosal cell and induce apoptosis

Question 21

Mechanisms of treatments for allergic disease (5)

Answer 21

General anti-inflammatory effects
Induction of regulatory T cells
Inhibit effects of mediators on specific receptors
Inhibit synthesis of specific mediators
Bind to IgE Fc region and prevent IgE binding to Fc receptor on mast cells

Question 22

Autoantibody target for autoimmune haemolytic anaemia (1)

Answer 22

Red blood cells

Question 23

Example of type 2 disease (4)

Answer 23

Autoimmune haemolytic anaemia
Goodpasture Syndrome
Graves disease
Immune thrombocytopenia
Myasthenia gravis

Question 24

Autoantibody target for goodpasture syndrome (1)

Answer 24

Glomerular basement membrane

Question 25

Autoantibody target for graves disease (1)

Answer 25

Thyroid stimulating hormone receptor

Question 26

Autoantibody target for immune thrombocytopenia (1)

Answer 26

Platelets

Question 27

Autoantibody target for myasthenia gravis (1)

Answer 27

Muscle acetylcholine receptor

Question 28

What kind of diseases do type 4 hypersensitive cause? (1)

Answer 28

Occupational diseases