Granuloma Formation

Question 1

Granuloma Formation

Answer 1

• Macrophages get infected with MTb bacilli
• Macrophages then release TNF and IL-12 → CD4+ T cell differentiation in Th1 cells
• Th1 cells produce:
  
  • IFN-gamma → activates macrophages → kill MTb bacilli or they aggregate to form granulomas
  • IL-2 → activates CTLs → kill MTb bacilli
• Th1 cells also surround macrophages infected w/ MTb bacilli
• Granuloma forms

Question 2

Caseous granuloma

Answer 2

• Classic TB granuloma
• Composed of epithelial macrophages, neutrophils, and a cuff of lymphocytes (all 3 main types)
• Center = necrotic state w/ dead macrophages. **Hypoxic **area. Contains multinucleate giant foam cells.
• Outer rim = fibrotic area

Question 3

Non-necrotizing granuloma

Answer 3

Consists primarily of some macrophages and lymphocytes

Question 4

Granuloma Remission

Answer 4

Resolution mediated by a shift toward **Th2 cells **that secrete IL-10 and TGF-beta → macrophage inactivation