1. PBL Session 3
Rosshini Jagatheswaran

2. Describe the
PATHOGENESIS of
bronchial asthma
MUST KNOW
Learning Outcome

3. How T helper cells work?

4. TH2cells
secrete cytokines IL-4, IL-5, IL-13
stimulate B cells to produce IgE and other
antibodies.
 IL-4 stimulates the production of IgE
 IL-5 activates locally recruited eosinophils
 IL-13 stimulates mucus secretion from
bronchial submucosal glands and also
promotes IgE production by B cells

6. Sensitization to Allergen
• Inhaled allergens
• TH2– dominated response
• IgE productions
• Eosinophil recruitment
• Release of granules and mediators

8. Allergen-Triggered Asthma
• Re-exposure
• Ag-induced cross linking of IgE bound to IgE
receptors on mast cell
• Mediators released – histamine, leukotrienes
• Tight junctions between epithelial cells open
• Antigen enter mucosa
• Mucosal mast cells activated
• Eosinophil release other mediators

9. • Leukotrienes
- constriction of bronchi  bronchospasm
- increased mucus production  mucosal
accumulation
• Histamine
- increased vascular permeability  swelling &
redness  edema
- increased mucus production  mucosal
accumulation
• Eosinophilic chemotactic factor
- Chemotaxis of eosinophils accumulation of
eosinophils

10. Late Phase
• Recruited leukocytes
initiate late phase
• Mediators release
from endothelium,
epithelial cells,
leukocytes
• Eosinophils  MBP,
ECP – damage
epithelium

12. Comparison of a normal bronchiole
with that in a patient with asthma
• Increase in the number of mucus-secreting
goblet cells in the mucosa and hypertrophy of
submucosal mucus glands  Accumulation of
mucus in the bronchial lumen
• Recruitment of eosinophils & macrophages
intense chronic inflammation
• Thickened basement membrane
• Hypertrophy & hyperplasia of smooth muscle
cells

13. POP-QUIZ
Which T Helper Cell plays an important
role in bronchial asthma?
What happens after IgE binds to the
mast cell in the first phase-sensitization
phase?
Leukotrienes causes …?
Upon re-exposure of Ag, what happens
after binding of IgE?

14. Some factors released by eosinophils in
the late phase causes damage to the
epithelium. Give 2 examples of the
factors.
Give 2 differences of a normal
bronchiole and bronchiole of an
asthmatic patient.

15. THANK YOU