Allergy Type 1
- Ig E
- Mast cell activation
Atopic allergy: sensitivity to allergens
Pathophysiology:
- Exposure to allergen (sensitisation)
Allergen taken up by dendritic cells and antigen expressed
Antigen bind to B-cell and T-cell differentiates
B-cell releases cytokines and IgE antibodies
IgE binds to mast cells
On subsequent exposure:
o Allergen binds to IgE on mast cells (early phase)
Mast cells degranulate releasing histamine, prostaglandin, leukotriene
These bind with tissues causing allergic reaction
Mast cell also recruits neutrophil and eosinophil
Eosinophil releases cytokines and attract B and T cells (late phase)
Effect of mast cell degranulation:
- Increase fluid and peristalsis (in GI causing vomit/diarrhoea)
- Swelling and mucus secretion (in nasal passage causing difficulty breathing)
- Increase blood flow and permeability of blood vessels (causes hypotension)
Types of allergic diseases
- Asthma
- Rhinitis
- Antgioedema (hives)
- Eczema
- Anaphylaxis (severe)
*Need prompt administration of adrenaline
Diagnosis:
- Skin prick test
o Patient should not be on antihistamine (false negative)
o Test allergens and controls (histamine-positive, saline-negative)
- Challenge test
Oral / inhaled / injected / skin given in increasing concentration and monitored
- Ig E
- Mast cell activation
Atopic allergy: sensitivity to allergens
Pathophysiology:
- Exposure to allergen (sensitisation)
Allergen taken up by dendritic cells and antigen expressed
Antigen bind to B-cell and T-cell differentiates
B-cell releases cytokines and IgE antibodies
IgE binds to mast cells
On subsequent exposure:
o Allergen binds to IgE on mast cells (early phase)
Mast cells degranulate releasing histamine, prostaglandin, leukotriene
These bind with tissues causing allergic reaction
Mast cell also recruits neutrophil and eosinophil
Eosinophil releases cytokines and attract B and T cells (late phase)
Effect of mast cell degranulation:
- Increase fluid and peristalsis (in GI causing vomit/diarrhoea)
- Swelling and mucus secretion (in nasal passage causing difficulty breathing)
- Increase blood flow and permeability of blood vessels (causes hypotension)
Types of allergic diseases
- Asthma
- Rhinitis
- Antgioedema (hives)
- Eczema
- Anaphylaxis (severe)
*Need prompt administration of adrenaline
Diagnosis:
- Skin prick test
o Patient should not be on antihistamine (false negative)
o Test allergens and controls (histamine-positive, saline-negative)
- Challenge test
Oral / inhaled / injected / skin given in increasing concentration and monitored
