Hypersensitivity And Allergy

Question 1

What is hypersensitivity?

Answer 1

The antigen specific immune responses which are either excessive or inappropriate and result in harm to host

Question 2

What 2 phases do hypersensitivity reactions have?

Answer 2

Sensitisation phase and effector phase

Question 3

What happens in the sensitisation phase?

Answer 3

Initial exposure to the antigen

Question 4

What happens in the effector phase?

Answer 4

There is re-exposure to the antigen

Question 5

What happens in a hypersensitivity type 1 reaction?

Answer 5

There is development of allergen specific antibodies resulting in mast cell degranulation

Question 6

What are the timings of onset for the different types of hypersensitivity reactions?

Answer 6

Type 1: immediate
Type 2: 5-12 hours
Type 3: 3-8 hours
Type 4: delayed 24-72 hours

Question 7

What happens in hypersensitivity type 2 reactions?

Answer 7

Antibody binds with cell surface antigen to activate compliment system resulting in tissue damage

Question 8

What treatment can be used for the cell/tissue damage caused by type 2 hypersensitivity reactions?

Answer 8

Anti-inflammatory drugs, plasmapheresis, splenectomy, intravenous immunoglobulin

Question 9

What treatment can be used for the physiological changes caused by type 2 hypersensitivity reactions?

Answer 9

Replacement therapy and correction of metabolism

Question 10

What happens in a type 3 hypersensitivity reaction?

Answer 10

Soluble antibody-antigen complex forms causing immune complexes to be deposited causing damage and disease development there

Question 11

What are some common sites of damage in a type 3 hypersensitivity reaction?

Answer 11

Joints, skin, small vessels and kidneys

Question 12

What are some examples of some type 3 hypersensitivity reactions?

Answer 12

Rheumatoid arthritis, glomerulonephritis, systemic lupus erythematosus

Question 13

What happens in a type 4 hypersensitivity reaction?

Answer 13

Antigen specific reaction driven by lymphocytes, macrophages and TH1 T cells

Question 14

Activation of mast cells in the deep dermis or epidermis cause which clinical feature?

Answer 14

Epidermis- urticaria

Deep dermis- angioedema

Question 15

What do we call the trend in allergy prevalence over time with age?

Answer 15

Allergic march

Question 16

Would does IgE mediated food allergy compare to non-IgE mediated with regards to: symptom onset, food types, presenting age and systems affected?

Answer 16

IgE mediated have an immediate onset of symptoms, caused by nuts, shellfish, fresh fruit and veg. Presenting age depends on age of contact. Can affect skin GI, Resp and CVS systems

Question 17

What diagnostic tests can be carried out for food allergy?

Answer 17

Skin prick tests, measuring IgE antibody levels and oral food challenges