Type 1 Hypersensitivity

Question 1

Define Allergy

Answer 1

Type I hypersensitivity reaction ie inappropriate immune response to an ALLERGEN : environmental non infectious antigen

Question 2

What are the mechanisms involved in type I hypersensitivity reaction ?

Answer 2

Abnormal TH2 response to allergen > IgE production > Mast cell activation

Question 3

What is the microbiome ?

Answer 3

Compete genetic content of microorganism that normally inhabit body

Question 4

What is Dysbiosis ?

Answer 4

Compositional or functional alterations to microbiome

Question 5

What causes damage in type I reaction ?

Answer 5

Mast cells activation when 2 IgE cross linked on mastcells surface by antigen causing release of granules

Mastcell armed with IgE from 1st exposure

Question 6

What are the main components of the mast cell granules and their main action ?

Answer 6

Tryptase : remodel CT
Histamine : permeability , vasodilation , bronchoconstriction
Cytokines ( IL) : TH2 response amplification, inflammation , eosinophil production
Chemokine
Leukotrienes : smooth muscle contraction, permeability

Question 7

Give eg of type I local reaction ?

Answer 7

Urticaria : mast cells epidermis , cytokine////Leuko

Angioedema : in deep dermis , histamine/bradykinin

Question 8

What is the mechanism of anaphylaxis and consequences ?

Answer 8

Systemic absorption of allergen (blood) causing Hypotension, Cardiovascular collapse , Generalised urticaria , Angioedema , Breathing pbm

Question 9

Which 2 therapies would prevent abnormal immune response in type I?

Answer 9

Oral immunotherapy : desensitisation to allergen by administration of increasing dose promoting TH1 response and regulatory cells

Anti-IgE monoclonal antibody

Question 10

Which treatments are available to stop mast cell activation?

Answer 10

Anti-histamine
Corticosteroids
Leukotrienes receptor antagonist