[A] 1.59 Tuberculum. Predominantly exudative and predominantly proliferative tuberculosis Flashcards
During tuberculosis infection, which specific lesions appear?
Tubercles (small granulomas)
Tuberculosis:
- Phylum
- Order
- Suborder
- Family
- Genus
- Phylum: Actinobacteria
- Order: Actinomycetales
- Suborder: Corynebacterinae
- Family: Mycobacteriaceae
- Genus: Mycobacterium
Mycobacterium bovis affects which species?
- Cattle
- Deer
- Goat
- Swine
- Dog
- Cat
- Humans
M. tuberculosis affects which species?
- Cattle
- Swine
- Dog
- Cat
- Humans
- Monkeys
M. avium affects which species?
- Cattle
- Swine
- Monkeys
- Birds
- Sheep
- Horses
Mycobacterium under the microscope
- Acid & alcohol fast coccoid rods
- Ziehl-Neelsen +
- Gram +
TB: General bacteriology
- Specific, resistant cell wall
- Replicates inside macrophages
- Obligatory pathogens, only in hosts
TB infection: Initial stages
- Macrophages phagocytose bacteria
- Fusion of lysosome & phagosome is blocked
- Primary TB - Replication within macrophages
*Three weeks later*
IL-12 activates TH1 response → Sensitisation phase
IL-12 is produced by…
- AP cells
- Toll-like-receptor-2 (TLR2)
TB infection: Sensitisation phase
- CD4+TH1 cells release IL-2 for further proliferation of T-lymphocytes
- Effector phase
TB infection: Effector phase
INFγ secretion → Macrophage activation
- Formation of phagolysosome
- Expression of NOS
- Formation of NO
- Damage of the Mycobacteria
Activated macrophages secrete TNFα & IL-1
- Fusion of langhans type giant cells
TB infection: Langhans type giant cell fusion causes…
Granuloma (tubercle) formation
- Type IV (delayed) hypersensitivity
TB infection: Summarise the steps
- Mycobacteria → Macrophages
- *3 weeks pass*
- IL-12 activates TH1 response
- Sensitisation phase
- Effector phase
- Activated macrophages → TNFα, IL-1
- Langhans type giant cells fuse
- Granuloma formation
Tubercle formtion can start with which processes?
Either:
- Exsudative process
- Proliferative process
Tuberculum: Starting with an exsudative process
- Exsudation, infiltration, regressive changes
- Necrosis of the central & serum infiltrated area
- Epitheloid cells & Langhans-type giant cells appear
Tuberculum: Starting with a proliferative process
- Proliferation
- Epitheloid cells, Langhans-type giant cells
- Epitheloid cells necrotise in the centre of the lesion
Both tuberculi starting with exudative and proliferative process both end with a…
A similar structure
Timeline of events of a TB infection in cattle
- 7 days: Early lesions - Intraalveolar macrophages, giant cells, neutrophils
- 14 days: In the tubercles, central neutrophil aggregates surrounded by epithelioid cells
- 21 days: Central necrosis in the tubercles
- 35 days: First mineralised lesions
Histological structure of the tubercle
- Central coagulative necrosis
- Karyolysis (Ø Nucleus)
- Proper vascularisation
- Calcification
- Macrophages - Epitheloid cells & Langhans-type giant cells
- A capsule containing lymphocytes & collagenous connective tissue with fibrocytes
Tubercle: Morphology
- Pinhead size, grey-white, shining foci →
- Necrosis: larger, opaque, yellowish in the centre
- Surrounded by granulation tissue
- Calcification in the centre
Different tubercle structures formed by TB
- Tuberculous cold abscess (Pyogenic bacteria)
- Tuberculous caverns (Histolysis followed by discharge via airways)
- Miliary TB (Multiple millet seed-sized lesions)
- Ulcers
Tuberculosis in birds: Granuloma structure
Foreign body type:
- Necrotic area is surrounded by foreign body giant cells radially → Palisade formation, Ø Central calcification
- Next zone: Histiocytes
- Only few lymphocytes
- Peripheral connective tissue
Tuberculosis in birds: Macroscopic morphology
- Tubercule
- Resorptive tubercles
- Tubercloconglomerates
- Larger nodules
Predominantly exudative & proliferative TB: Overview
Lack of the Th1-type response: Ø Granuloma formation
- Ø:
- Necrosis
- Calcification
- Foci (tuberculum)
- Larger, tumour-like lesions (fibrosarcoma) produced
Predominantly exudative & proliferative TB: Stages of development
- Granulation tissue proliferates
- Scattered connective tissue cells + Histiocytes + giant cells in foci →
- Tuberculous granulation tissue
If there are only histiocytes + Giant cells → Great cell granulation
TB fibrosarcoma: Description
- Greyish
- Homogenous
- Infiltrative lesion
- No sharp demarcation
What is shown?
Predominantly proliferative tuberculosis in a dog
M. avium subsp. hominissuis
- Note:
- Enlarged Peyer’s patches
- Enlarged mesenteric lymph node
Predominantly exudative TB
A disadvantage of the higher organism
- Exudation → Ø Cellular reaction
- Coagulation & necrosis → Caseation → Demarcation
Predominantly exudative TB affects which organs?
Those with a loose structure:
- Lungs
- Udder
- Lymph nodes
- Uterus
- Kidneys
