resp 2

Question 1

what is the main cause of TB

Answer 1

mycobacterium tuberculosis

Question 2

what is tb

Answer 2

bacterial infection into alveoli
chronic inflammatiory response due to factors in bacterial wall
infection can be asymptomatic

Question 3

what are the factors that predict the outcome of TB

Answer 3

number of organisms ingested (bacterial load)
immune response - malnutrition, infancy, old age, poor-underpriveleged, overcrowded environments, co-morbidities, immunosuppressive therapy or drug-dependent
admin of appropriate antibiotics

Question 4

what determines the disease pattern for TB

Answer 4

primary infection = first exposure to bacteria
secondary infection: previously exposed individual
can go from primary -> secondary -> milliary
or primary -> primary progressive -> miliary

Question 5

what are the stages of primary TB development

Answer 5

exposure to myobacterium tuberculosis 
alveolar macrophage endocytosis 
t lymphocyte hypersensitivity
cell-mediated immune response 
granuloma formation

Question 6

describe stage 1 of TB = exposure to m. tuberculosis

Answer 6

uninfected person inhales infected aerosols

bacili avoid standard defence mechanisms and move into lung alveoli

Question 7

describe stage 2 TB = alveolar macrophage endocytosis

Answer 7

Macs engulf but cant degrade m.tb because of cell wall lipids
mtb remains within macphag
no lysosome fusion => no antigen processing
bacilli replicate slowly within macs every 16-20 hrs
some macs carry bacilli to regional lymph nodes
can disseminate by blood = ghon complex => legions

Question 8

describe 3rd stage of TB = T lymphocyte hypersensitivity

Answer 8

macs degrade some bacteria = present antigen to T lymphs =>

takes 3 weeks for T helper response hypersensitivity reaction

Question 9

describe the 4th step primary TB development = cell mediated immune response

Answer 9

Th1 cells => interferon gamma => activate macs to become bactericidal = inc conc of lytic enzymes + stim formation of phagolysosome
now act macs can contain infection

Question 10

describe 5th stage primary TB development = granuloma formation

Answer 10

T helper cells = forming granuloma + caseous necrosis
epitheliod macs form giant cells
also secrete TNF to recruit more monoccytes

Question 11

what are the main features of granuloma formation in primary TB

Answer 11

1. central area of caseous necrosis
2. surrounded by act macs
3. giant cells
4. lymphocytes
5. fibroblasts

Question 12

describe the 6th stage of primary TB = healed or latent lesions

Answer 12

healed lesion = immune response destroys bacteria => scar tissue
latent lesion = mtb adapt to env by changing their metabolism = slow down replication inc cell wall thickness, enter dormant state and can be reactivated

Question 13

describe the pathogenesis of primary tb, focusing on ghon complex

Answer 13

1. ghon focus = granuloma in periphery of lung w/organisms
2. lymph node involvement for help from lymphocytes
3. altogether = ghon complex

Question 14

describe the pathogenesis of progressive primary TB

Answer 14

high bac load/inc bac virulence/immunosuppression
-local progression = lesion enlarges, large areas of caseous necrosis causing cavities, expand to lower lobe
dissemination disease = miliary TB

Question 15

what is miliary TB

Answer 15

prganisms drain through lymphs to venous blood and circulate back to lungs via pulmonary arteries

Question 16

describe the pathogenesis (2 steps) of secondary TB

Answer 16

reactivation of dormant disease from old granuloma

reinfection = newly acquired bacs

Question 17

what do you see in path pots for secondary TB

Answer 17

destruction of lung with cavitations
apcial lesions bc high o2 content at apex
little lymph invovlement bc pre-existing hypersensitivity. -> prompt infmam response that partition infection
t-cell mediated immune response is familiar with TB antigens -> tissue necrosis and production of cavities

Question 18

what are the outcomes of secondary TB

Answer 18

can be asymptomatic
symptoms from cystokines and ac macs (malaise, fever)
progressive pulm involvement -> purulent sputum
cured with prolonged antibiotics except for resistant strains
best outcome = calcification of apical TB be collagen deposition around granuloma

Question 19

what outcomes can occur in secondary TB if there are problems with the legions

Answer 19

apcial lesion can enlarge until tissue is destryoed

1. lesions erodes BV =miliary spread, haemoptysis (gonnac ough blood)
2. lesion erodes bronchi = tuberculous bronchopreumonia
3. lesion invades pleura = pleuritic pain, tuberculous empyema (caseous necrosis within pleural cavity)

Question 20

what is tuberculous bronchopenumonia

Answer 20

outcome of bronchi erosion bc of legion expansion
infected lymph node erodes into bronchus
living bacilli pass down bronchi and bronchioles )gravity)
infection spreads -> granulomatous lesions -> galloping consumptions = fatal