TB Flashcards
What type of hypersensitivity reaction is a TB infection?
Type 4- delayed
What is the characteristic pathology of TB?
Granulomas, caseating necrosis
Why is TB so successful?
It can aviod phagocytosis due to thick cell wall and coating
It can stimulate a T cell response
Can M. bovis be seen in humans?
Yes common in the developing world due to M. bovis in the milk
What enhances the macrophage ability to kill mycobacteria?
T cell response
What is primary TB?
Infection following the first exposure and up to 5 years later.
What happens when TB enters the lungs?
Phagocytosed and carried to hyler lymph nodes
=> immune activation and granulomatous formation
Usually kills organism but in few cases infection is overwhelming and spreads
What is secondary TB?
Reinfection/reactivation of TB in someone with some immunity
What is the pathogenesis of secondary TB?
Disease remains in in the apicies of lungs and can progress/ spread to airways and lungs
What tissue changes are seen in primary TB?
Ghon focus in peripheries and mid zones of the lung
Large hyler lymph nodes
What tissue changes are seen in secondary TB?
Fibrosing and cavitating apical regions
What is millary TB?
TB in the blood spreading to different areas of the lung
High frequency of mycobacterial organisms
Why does TB reactivate?
Decreased T cell function:
Age >70
Coincident disease- HIV
Immunosuppressive therapy- steroids, chemotherapy
Why can TB cause a reinfection?
Higher dose of mycobacterium
More virulent dose of mycobacterium
