Hypersensitivity & anaphylaxis

Question 1

Define hypersensitivity.

Answer 1

An inappropriate & excessive immunological reaction to an external antigen due to dysfunctional control of the immune system

Question 2

What are the 4 types of hypersensitivity reactions?

Answer 2

Immediate or IgE-mediated

Antibody-dependent

Immune complex

Delayed or cell-mediated

Question 3

What are the mediators in Type I hypersensitivity reactions?

Answer 3

IgE + mast cells, esosinophils, basophils

Question 4

What are the mediators in Type IV hypersensitivity reactions?

Answer 4

T lymphocytes + macrophages

Question 5

List some examples of Type IV hypersensitivity reactions.

Answer 5

Allergic contact dermatitis

Chronic transplant rejection

Multiple sclerosis

Tuberculin skin test

Question 6

Describe the pathophysiology of Type I hypersensitivity.

Answer 6

Antigen activation of Th2 cells and stimulation of IgE class switching in B cells. IgE binds to FcERI on mast cells. On subsequent exposure, allergen binds to mast cell bound IgE and causes degranulation

Question 7

What are the main 4 medications to administer in anaphylaxis?

Answer 7

Adrenaline (500mcg) IM

IV chlorphenamine

IV hydrocortisone

Nebulised salbutamol