Hypersensitivity

Question 1

Type 1

Answer 1

Anaphylactic

Antigen reacts with IgE bound to mast cells

Question 2

Type II

Answer 2

Cell bound
IgG or IgM binds to antigen on cell surface

Autoimmune haemolytic anaemia, ITP, Goodpastures

Question 3

Type III

Answer 3

Immune complex
Free antigen and antibody combine (IgG IgA)
Serum sickness, SLE, post-strep glomerulonephrotis, extrinsic allergic alveolitis (esp acute phase)

Question 4

Type IV

Answer 4

Delayed hypersensitivity
T cell mediated
Tuberculosis, tuberculin skin reaction, graft v host, allergic contact dermatitis, scabies, extrinsic allergic alveolitis (esp chronic phase)

Question 5

Type V

Answer 5

Stimulated hypersensitivity
IgG antibiodies stinulate cells they are directed against
graves, myasthenia gravis

Question 6

Skin prick test

Answer 6

Drops of dilute allergen onto skin
Histamine (+ve) and water (-ve) controls
Wheal in 15mins if allergy

Food/pollen/wasp/bee

Question 7

RAST (radioallergosorbent test)

Answer 7

Amount of IgE that reacts with allergen
Grade 0 (negative) to 6 (strongly positive)

Can be used if skin prick not possible eg extensive eczema or taking antihistamines

Question 8

Skin patch testing

Answer 8

Contact dermatitis
30-40 allergens
Results read 48hrs later by dermatologist