Asthma and allergy

Question 1

Briefly explain key Ig and cell mediating a type 1 hypersensitivity reaction.

Include 2 conditions resulting from this reaction

Answer 1

IgE - during 1st exposure formed by class switching due to IL-4 secretion.

mast cells - during 1st exposure IgE binds to mast cell with Fc region, sensitising it. during 2nd exposure they recognise allergen, degranulate and release histamine.

anaphylaxis, acute urticaria, allergic rhinitis (hay fever), asthma and food allergy

Question 2

name 3 cells that mediate type 4 hypersensitivity reactions

Answer 2

TH1
Th2
CTL

Question 3

penecillin is a drug that in some patients has the ability to provoke an inappropriate immune response. Briefly describe the mechanism of this

Answer 3

Type 2 hypersensitivity reaction.

soluble drug binds to cell surface (RBC/platelets) –> IgG binds to complex –> macrophages and complements recruited

Question 4

explain the stages of mast cell priming against an allergen

Answer 4

1st exposure to pollen –> dendritic cells take up pathogen –> present on MHC2 to CD4+ cells (Th2) –> activating them –> producing IL-4 and IL-13 –> driving IgE production (B-cells detect allergen and start IgE production) –> allergen specific IgE binds to mast cell priming for 2nd exposure

Question 5

what is the function of filaggrin and why does a deficiency cause atopic dermatitis?

Answer 5

It’s a protein that maintains skin integrity. Decreased filaggrin allows allergens to infiltrate skin, causing increased risk of type 1 hypersensitivity /allergic reaction

Question 6

name 3 physiological effects of mast cells due to histamine release

Answer 6

vasodilation/increased blood flow
bronchoconstriction 
increased vascular permeability/oedema 
activation of nerve cells/flare
increased secretion 
increased peristalsis

Question 7

describe 2 structural changes in chronic inflammation of the airways and name 1 cells involved in these changes

Answer 7

narrowing of airway due to thickened muscle, increased mucus secretion.
Hypertonia of muscle
Th2 or eosinophils

Question 8

a drug addict is admitted to hospital after mistakenly injecting himself with a high dose of soluble antigen instead for heroin. The doctor tells you this patient has serum sickness. What type of reaction is this and explain why the patient has red blotches on his skin (burst capillaries)

Answer 8

Type 3 hypersensitivity reaction involving IgM/G binding to soluble antigen in serum.
Ig binding to small antigen causes small immune complexes to form (no agglutination) –> which deposit into vessel walls –> recruiting complements –> inflammatory response –> damaging neighbouring tissues –> causing them to burst