Immunodeficiencies (Allergies)

Question 1

Identify the four different types of hypersensitivity reactions

Answer 1

• 1. immediate hypersensitivity (mast cell driven )

2. cytotoxic : reponsive to alternated components of human cells (eg: penicillin-erythrocyte epiotypes) IGG DRIVEN
   (eg: Graves/ Myasthenia gravis) derived from receptor blockage effecting neuromuscular function
   - haemolytic disease in neonates (RhD -ve mother v. RhD +foetus causing erythrocyte destruction in child)
3. serum sickness and ARTHUS reaction
   soluble antigen + igG = COMPLEMENT damage associated to ⬆️inflammatory antibody-antigen complex, Fc-𝛾 binding to mast cells deposited in blood vessel walls = tissue dysfunction which
   (eg: tetanus reaction/ temporary ) can cleared by phagocytes
   chronic = thrombosis
4. delayed hypersensitivity (contact-dermatitis)
   eosinophil activation Th-1 response triggers ⬆️ pro-inflammatory, localised chemokine and cytokines (Mantou’s Test) (Tuberculosis-leprosy)
   - effector mechanism of allergen immune response
   - allergic asthma
   - systemic anaphylaxis

Question 2

Understand the production of allergen-specific IgE

Answer 2

• allergen specific IgE
  antigen crosslinks to mast-cell basinophils via IgE which ⬆️ vasodilation factors
• systemic/ localised anaphylaxis
• eczema

Question 3

Understand the role of cells and inflammatory mediators in the allergic immune response

Answer 3

. serum sickness and ARTHUS reaction
soluble antigen + igG = COMPLEMENT damage associated to ⬆️inflammatory antibody-antigen complex, Fc-𝛾 binding to mast cells deposited in blood vessel walls = tissue dysfunction which
(eg: tetanus reaction/ temporary ) can cleared by phagocytes
chronic = thrombosis
inhaled = Farmers lung (from foreign antigens)

Question 4

Understand asthma in the context of allergy

Answer 4

ALLERGEN:
- danders
- pollens
- dust mite feaces
inflammatory mediation causes inflammation and ⬆️mucus secretion = airway obstruction
- cells recruited from circulation

Question 5

Understand the basic concept of the “hygiene hypothesis”

Answer 5

too clean => removes infections so immune responses aren’t exercised
cleaner the environment = increased risk of allergies

Question 6

How does mast cell activation work?

Answer 6

FcℇR1 binding causes ⬆️ granules containing histamine (IL-4 histamine releasing factor)
- igE crosslinks causes release of granules