B3 Allergy Testing

Question 1

Describe body consequences to Anaphylactic Shock (5)

Answer 1

Systemic response (non-localised)
Increased vascular permeability
Swelling of lips, tongue and larynx
Smooth muscle contraction in lungs
Fall in BP
Possibility death

Question 2

Describe passive cutaneous anaphylaxis (carry out in rats)

Answer 2

Rats injected via IV with evans blue
Rats injected with serum from patient
Ab diffuse into tissue
Any IgE will bind FcR on rats mast cells
Test allergen is injected intradermally
Allergen is bound by mast cell specific IgE
IgE cross-linking occurs
Mast cell degranulation
Increased vascular permeability
Evans blue escapes into skin wheal & flare reaction

Question 3

Describe skin testing for allergy

Answer 3

Persons back marked into grids & small doses of allergens applied and skin scratched
Back is examined after 30mins for characteristic wheal and flare reaction

Question 4

Describe Radioimmunosorbant (RIST) assay

Answer 4

disks w/ anti-IgE is incubated with serum sample (binds)
Radiolabelled anti-IgE is added, washed and amount radioactivity recorded
–> only reveals if IgE is elevated

Question 5

Describe Radioallergosorbant (RAST) assay

Answer 5

disks w/ allergens (IgE) incubated w/ serum sample
anti-IgE-radiolabelled antibody added and washed, amount radioactivity recorded
–> Determines which allergens a person responds to

Question 6

Describe differences between RIST & RAST

Answer 6

RAST can determine which allergens a person responds
(A for allergen)
RIST can only determine if a person has elevated IgE
(I for immunoglobin)

Question 7

Describe Future-Protein arrays

Answer 7

Miniaturization & testing of hundreds of different antigens on a micro array
Replacement of radio-label by fluorescent label
Much quicker (automated) & more info provided
Uses flow cytometry
(also Adaptable: can be used as a capture system too (e.g. measuring cytokines in serum)

Question 8

Therapy for allergy

Answer 8

Antihistamines block release or action of histamines

Increasing doses of antigen injected subcutaneously results in a shift from IgE to IgG production

Question 9

Bead Arrays Advantages

Answer 9

Similar to Protein Arrays
Can mix and match beads to make custom arrays for individual patients
Easily quantifiable