Hypersensitivity

Question 1

What is type I hypersensitivity

Answer 1

Allergy

Question 2

What is the definition of hypersensitivity

Answer 2

A state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent

Question 3

What is an allergen

Answer 3

An antigen that causes an allergic reaction

Question 4

What types of reaction is a type 1 hypersensitivity reaction

Answer 4

IgE mediated reaction

Question 5

What immune cells are involved in type 1 hypersensitivity reaction

Answer 5

Mast cells
Basophils

Question 6

Give some examples of type 1 hypersensitivity reaction

Answer 6

Atopy
Anaphalaxis

Question 7

What type of reaction is type II hypersensitivity

Answer 7

Cytotoxic responses

Question 8

What immune cells are involved in type II

Answer 8

NK cells
Complement
T cells

Question 9

What is an example of type II

Answer 9

Haemolytic anemia

Question 10

What reaction is type III hypersensitivity

Answer 10

Immune complex responses

Question 11

What immune cells are involved in type III

Answer 11

Complement
Neutrophils

Question 12

What is an example of type III

Answer 12

Serum sickness

Question 13

What type of reaction is type IV

Answer 13

Cell mediated response

Question 14

What immune cells are involved in type IV

Answer 14

T cells
Macrophages

Question 15

Give examples of type IV

Answer 15

Sracoidosis
TB
Crohn’s disease

Question 16

What is anaphylaxis

Answer 16

Actuate serious allergic response

Question 17

What are allergens

Answer 17

Can be proteins, have ability to elicit an immune response

Question 18

What are happens

Answer 18

Any small molecule that can be recognised by a specific antibody but cannot elicit an immune response

Question 19

What are the main roles of mast cells and basophils

Answer 19

• immune cell recruiter
• neurotransmitter
• vasodilator
• endothelial constrictor
• bronchoconstrictor

Question 20

Give some cutaneous atrophy examples of type I hypersensitivity reactions

Answer 20

Localized
- allergic rhinitis (hay fever)
- atopic dermatitis (allergic eczema)
- asthma (Lower respiratory tract)

Question 21

What is systemic anaphylaxis

Answer 21

Anaphylactic shock throughout the whole body

Question 22

Give some examples of allergy tests

Answer 22

• skin prick and patch test
• blood test - measures IgE in the blood
• food challenge

Question 23

Name some drugs that can be taken for allergies

Answer 23

• anti histamines
• epinephrine
• hydrocortisone
• cromoglycate

Question 24

Function of antihistamines

Answer 24

Compete with histamine receptors

Question 25

Function of epinephrine in anaphylactic shock

Answer 25

Best immediate treatment, reverses effect of granules (vasoconstriction, relaxes muscles)

Question 26

Name immunological treatment for allergies

Answer 26

- hypo or de sensitisation - IgE or IgG production

Question 27

What is the mechanism for epinephrine

Answer 27

— stimulation of adrenoreceptors - improves blood pressure - reverses peripheral vasoconstriction - causes bronchodilation - reduces inflammatory mediator response

Question 28

What does type II arise from

Answer 28

Antigen-antibody complex arising IgG and IgM binding to antigenic cell

Question 29

Type II hypersensitivity is lysed by

Answer 29

- membrane attack complex formation (complement) - antibody dependent cell mediated cytotoxicity (natural killer cells or CD8 + T cells) - common example - transfusion reactions/autoimmune haemolytic anaemia

Question 30

Describe what happens when mismatched blood type is transfused in an individual

Answer 30

The body attacks the red blood cells, immune cells recognise the antibodies on the blood cells as a foreign invader and attack them

Question 31

Describe type III hypersensitivity

Answer 31

- involves reactions against soluble antigens circulating in serum - antibody - antigen immune complexes are deposited in organs which leads to - complement activation, neutrophil recruitment, inflammation mediated damage

Question 32

What are some examples of type III hypersensitivity

Answer 32

- Arthus reaction - serum sickness - oral erythema multiforme (EM)

Question 33

What happens during rheumatoid arthritis

Answer 33

Immune complexes deposited in tissues activate a complement which attracts neutrophils to the site

Question 34

What are some examples of type III hypersensitivity reactions

Answer 34

- arthus reaction (localised hypersensitivity reaction) - antibody - antigen complexes are localised - can arise from injected particles (eg booster vaccines) or inhaled or injected antigens

Question 35

Serum sickness is an example of a …. Reaction

Answer 35

Arthus reaction

Question 36

Describe oral erythema multiforme (EM)

Answer 36

- characterised y crusty blistering of oral mucosa - caused by deposition of immune complexes (IgM bound immune complexes) in the microvasculature of the oral mucous membrane - can be acute inflammatory response to viral infections eg HSV - can be caused by hypersensitivity drugs eg.Trimethroprimsulfamethoxazole which treats UTI’s

Question 37

Describe type IV hypersensitivity

Answer 37

- T cell mediated hypersensitivity (no antibodies) - sometimes called delayed hypersensitivity as it takes time to recruit T cells - localized T cell reaction at site of antigen exposure (eg contract dematitis) - involves both CD8+ T cells (direct damage of cells - cytotoxicity)

Question 38

What are some examples of type IV hypersensitivity

Answer 38

- contract dermatitis - tissue graft rejection - response to Intracellular pathogens - orofacial granuloamatus