TB

Question 1

what feature of TB bacteria make them resistant to enzymes released by macrophages after phagocytosis

Answer 1

thick waxy cell wall

Question 2

what is latent TB

Answer 2

tb more likely tobe spread in over crowded living conditions
when someone is infected with TB but develops immunity &
doesnt develop the disease
-they have TB bacteria which do not multiply
-they arent unwell and show no symptoms
-they cannot pass the disease onto others

Question 3

active TB

Answer 3

-has bacteria which can actively multiply
-will be sick, show symptoms and can pass it onto others

Question 4

3 weeks into primary TB, what happens

Answer 4

cell mediated immunity begins

immune cells surround site of infection and from a GRANULOMA

Question 5

granuloma

Answer 5

attempt to wall off foreign substances like pathogens so they cant spread

Question 6

what happens to tissue inside granuloma as a result of it

Answer 6

dies, caseous necrosis

Question 7

what is the area of dead tissue called

Answer 7

ghon focus

Question 8

ghon complex

Answer 8

TB reaches hilar lymph nodes by extension of ghon focus or through lymph and causes caseation there aswell

caseating tissue along with lymph node=ghon complex

usually in lower lobes of the lungs

Question 9

what happens next to tissue encapsulated by granuloma

Answer 9

undergoes fibrosis & calcifies

this produces scar tissue that can be seen via x-rays

Question 10

ranke complex

Answer 10

calcified ghon complex

in some cases the TB micro bacteria are killed by the immune system & dont come back

in other cases the bacteria are still viable just walled off, if the hosts immune system becomes compromised the ghon focus can become reactivated & infection can be spread to either one or both upper lobes of the lungs
(upper lobes where oxygen levels are the greatest, better for TB)

Question 11

what happens if TB reactivates and spreads

Answer 11

memory cells recognise tb and release cytokines to control new outbreak, but this causes more caseous necrosis which form cavities this time allowing the bacteria to disseminate or spread through airways or lymphatic channels to other areas of the lungs

Question 12

systemic miliary TB

Answer 12

Cavities in new areas of caseous necrosis after cytokines released can allow TB to spread to other areas of the lungs causing bronchopnemonia or spread via the vascular system infecting nearly every other tissue in the body

Question 13

kidneys

Answer 13

lots of white blood cells in kidneys can lead to a high conc in urine

Question 14

meninges of brain

Answer 14

can lead to meningitis

Question 15

lumbar vertebrae

Answer 15

potts disease

Question 16

adrenal gland

Answer 16

addisons disease

adrenal glands dont produce enough hormones like cortisol and aldosterone, fatigue, skin darkening

Question 17

liver

Answer 17

hepatitis

can lead to cirrhosis orcancer

Question 18

cervical lymph nodes

Answer 18

lymphadentitis in the neck

Question 19

testing for TB

Answer 19

-PPD skin test
-tuberculin (part of TB bacteria) injected into skin, if person has already been exposed to TB their immune system will react & produce a small localised infection within 48-72 hours

test positive if theres a large enough area of inflammation and hardening of tissue

this test only shows if patient has previously been exposed to TB
DOESNT show if its latent or active

Question 20

interferon gamma release assays

Answer 20

-look for evidence in blood of previous exposure to TB proteins
-more specific to tb than other mycobacterial infections than ppd skin tests
-unlikely to show positive due to having tb (bcg) vaccine in the past

-if ppd skin test or interferon gamma release assay test comes back positive patient may get chest x-ray
to look for signs of active tb disease

-samples from sputum or broncheolar lavage can be collected & sent for staining and pcr to check for evidence of tb

Question 21

treatment of latent tb

Answer 21

-single drug taken for long period of time like isoniazid for 9 months

Question 22

treatment of active tb

Answer 22

-combinations of different antibiotics used
-results in patients being non-infectious usually within a few weeks
-as infectious patients kept in negative pressure rooms
-visitors required to wear masks
that cant filter out oil aerosols
but can filter out all other aerosols, including tb
-still kept on drugs even after no longer infectious

Question 23

antibiotic resistant TB

Answer 23

-becoming more common
-wont be killed by usual antibiotics
-identify which strain is present in patient to see if its antibiotic resistant
-use multiple drugs at once to prevent antibiotic resistance developing (less survivors that can reproduce passing on alleles that give them resistance to an antibiotic)
-medications need to be used for entire course of therapy
so that all tb is killed

Question 24

specific vs non specific immune respone

Answer 24

non-specific=same response regardless of the pathogen
use of inflammation, interferons and phagocytosis

specific=response specific to a particular pathogen

Question 25

how is the immune system able to recognise specific pathogens

Answer 25

antigens on their cell surface glycoproteins that can be recognised by the immune system as self or non-self

Question 26

inflammation

Answer 26

-surrounding area of wound swollen, warm and painful -mast cells respond to tissue damage by secreting the molecule histamine -histamine=chemical signalling molecule that allows communication between cells

Question 27

what does histamine stimulate?

Answer 27

vasodilation-increasing blood flow through capillaries -vasodilation capillaries walls become leaky/more permeable allowing fluid to enter the tissues and create swelling -more permeable capillaries causes phagocytes to leave bloodstream and engulf foreign particles -cell releases cytokines, cell signalling molecules that trigger an immune response in the area

Question 28

interferon function

Answer 28

-part of non-specific immune reponse -anti-viral proteins released when cells are infected with viruses -prevent viruses from spreading to uninfected cells -inhibit production of viral proteins which prevents virus from replicating -activate WBCS involved in specific immune response which can destroy infected cells -they increase non-specific immune response e.g. by increasing inflammation

Question 29

phagocytosis

Answer 29

-WBCS -remove dead cells and invasive microorganisms by engulfing and digesting them-phagocytosis -travel around body in blood stream and leave blood through capillary walls

Question 30

how do phagocytes attack pathogens?

Answer 30

-recognise antigen on cell surface of pathogens as being non-self -ENDOCYTOSIS-->cell surface membrane of phagocyte reaches out around pathogen, engulfing it -pathogen trapped inside phagosome/phagocytic vacuole -lysosome fuses with phagosome releasing digestive enzymes into phagosome -digestive enzymes (including lysozyme) digest the pathogen -after pathogen digested the phagocyte will present the antigens of the pathogen on its CELL SURFACE MEMBRANE - now the phagocyte is an APC -presentation of antigens initiates the specific immune response

Question 31

how're phagocytes attracted to the infected area?

Answer 31

by chemicals released by pathogens or by chemicals released by the body cells under attack like histamine

Question 32

tubercles

Answer 32

tissue infected by tb infection undergoing caseous necrosis and being encased in a granuloma bacteria dormant in tubercles

Question 33

first symptoms of tb

Answer 33

-fever -fatigue -coughing -lung inflammation

Question 34

later effects

Answer 34

extensive damage to lungs which can lead to death due to respiratory failure can enter bloodstream where it can spread to organs causing organ failure