CSIM 1.46/1.47 - Allergic Disease 1 + 2

Question 1

Define allergy?

Answer 1

Hypersensitivity reaction initiated by immunological mechanisms - will react to the substance each and every time

Question 2

Define hypersensitivity?

Answer 2

Objectively reproducible symptoms initiated by exposure to a defined stimulus at a dose tolerated by normal subjects

Question 3

Which antibody is involved in mediating type 1 hypersensitivity reactions?

Answer 3

IgE

Question 4

Describe how type 1 hypersensitivity reactions occur?

Answer 4

Initial encounter with allergen - Th2 cells become activated which stimulates B-cells to secrete IgE - this binds to mast-cells and when Ag re-encountered it binds directly to the IgE on the mast-cells and via cross-linking - degranulation occurs

Question 5

Which receptor does the IgE bind to on the mast cells?

Answer 5

FCeR.1 receptors

Question 6

Degranulation of mast cells lead to the release of what substances?

Answer 6

Histamine
Leukotriene
Prostaglandin
Prostacylin

Question 7

What is atopy and name some examples of atopic diseases?

Answer 7

Tendency to produce IgE in response to low doses of allergen
Eczema
Food allergies
Rhinitis 
Asthma

Question 8

Which antibody is involved in mediating type 2 hypersensitivity reactions?

Answer 8

IgG

Question 9

Describe how type 2 hypersensitivity reactions occur?

Answer 9

Hapten bings to cells forming ‘cell/matrix-associated Ag’

The body produces IgG to counter the complex - activating phagocytes to destroy them

Question 10

Which antibody is involved in mediating type 3 hypersensitivity reactions?

Answer 10

IgG

Question 11

Describe how type 3 hypersensitivity reactions occur?

Answer 11

IgG/Ag complexes are identified by complement proteins and a complement cascade initiates leading to vasculitis

Question 12

Name a clinical condition brought about by type 3 hypersensitivity reactions?

Answer 12

Serum sickness

Question 13

Describe how type 4 hypersensitivity reactions occur?

Answer 13

Ag reacts and activates Ag specific T-cells - leads to inflammation and attraction of leukocytes

Question 14

What two tests can be used in identifying allergies?

Answer 14

Patch test
Mantaux test (SC) - specifically for tuberculin

Question 15

Define anaphylaxis?

Answer 15

IgE mediated immunological response - granules released from mast cells and basophils leads to systemic hypersensitivity with rapid onset
Respiratory compromise and end-organ failure may present

Question 16

Name four critical steps in the management of an anaphylaxis incident?

Answer 16

Lie patient down (NEVER stand up)
Intramuscular Epinepherine
Salbutamol
Serum tryptase

Question 17

Name the four main causes of anaphylaxis?

Answer 17

Insect stings
Latex
Food allergies
Drug intolerances

Question 18

What species of insect most commonly leads to anaphylaxis?

Answer 18

Hymoneptera

Question 19

Which hypersensitivity reactions may be initiated by latex allergies?

Answer 19

Type 1 (natural sap)
Type 4 (specific chemical within the latex)

Question 20

What is the difference between food allergy and food intolerance?

Answer 20

Food allergy is immune mediated

Question 21

Name a non-IgE mediated food allergy?

Answer 21

Coeliac disease