immunity to bacteria

Question 1

are bacteria intracellular or extracellular ?

Answer 1

can be both

Question 2

when dealing with a bacteria what must the immune response deal with ?

Answer 2

the bacteria , the infected cells and the viral toxins

Question 3

how does the innate response recognise the pathogen ?

Answer 3

through the PAMP’s

Question 4

how does the acquired recognise the pathogen ?

Answer 4

through the B or T cell recognising the specific antigen

Question 5

how can phagocytic cells remove bacteria ?

Answer 5

using phagocytosis or produce toxic products e.g. tumour necrosis alpha, superoxide, nitric oxide

Question 6

what are the most numerous cell in the body ?

Answer 6

neutrophils

Question 7

what occurs if the bacteria goes systemic ?

Answer 7

it is very difficult to control and treat

Question 8

how would the body deal with a local gram negative infection of bacteria ?

Answer 8

the macrophages are activated to secrete TNF alpha a cytokine causes apoptosis and this increases the plasma proteins into the tissue. This in turn increases phagocytosis

Question 9

how does the body deal with a systemic infection of gram negative bacteria?

Answer 9

the macrophages are activated in the liver and spleen to secrete TNF alpha into the blood stream. This causes swelling and a decreased blood volume.

Question 10

why is it important to have lot’s of PRR’s ?

Answer 10

so if the pathogen blocks one then the cell can still recognise it

Question 11

what are NET’S ?

Answer 11

neutrophil extracellular traps

Question 12

what do the NET’s do ?

Answer 12

they immobilize the bacteria at the site of infection. Also special cell death program occurs , it is a specialised type of apoptosis called ‘NETosis

Question 13

what is MPO ?

Answer 13

myeloperoxidase it is only produced from neutrophils and has a bleach like effect.

Question 14

what can the bacteria cause the macrophages to release ?

Answer 14

IL-6 which is a proinflammatory cytokine acts on the hepatocytes to induce the synthesis of acute phase proteins in response to the damage and they are used to control the infection as the innate system.

Question 15

what does the C reactive protein bind to on the bacterial surface to opsonise it ?

Answer 15

the phosphocholine which also activates complement

Question 16

the bacteria can also produce super antigens , what are these ?

Answer 16

class of proteins that can activate a large population of T cells. They work by activating the T cell but not through the receptor. This can lead to toxic shock.

Question 17

when is bacteria more easily phagocytosed ?

Answer 17

when it is clumped together

Question 18

how is apoptosis induced by innate cells ?

Answer 18

when TNF alpha is produced by macrophages and neutrophils

Question 19

what is staphylococcus aureus ?

Answer 19

This is a gram-positive bacterium that is extracellular . It causes both community and hospital-acquired infections

Question 20

what is important in the innate when controlling ?

Answer 20

neutrophils are important

Question 21

when is phagocytosis more efficient ?

Answer 21

if complement or antibody - IgG coats the bacteria

Question 22

how do the neutrophils cause killing ?

Answer 22

superoxide, hydrogen peroxide, kill the bacteria in phagosome.
granules present – toxic products – e.g. defensins, lysozyme and bacterial permeability increasing protein and this kills the bacterium in phagosome.
They are also phagocytic

Question 23

how can the S.aureus evade the detection ?

Answer 23

They can produce and secrete and surface-bound molecules that inhibit neutrophils activity. This also inhibits the neutrophil recruitment. As well as,
• Inhibit bacterial binding to neutrophils
• Inhibit phagocytosis by neutrophils
• Inhibit toxic products produced by neutrophils

Question 24

what does the mycobacterium tuberculosis cause ?

Answer 24

a lung disease TB

Question 25

where does the bacteria live ?

Answer 25

inside the macrophage

Question 26

how do you kill the TB ?

Answer 26

stimulate the macrophages to kill by IFN gamma. The nitric oxide and reactive nitrogen intermediates are important. Apoptosis of infected macrophage – NK/Tc release TNF alpha can induce apoptosis. A granuloma can form an multicellular structures that limits growth of Mt.

Question 27

the infected macrophage secreates more IL -10 , why ?

Answer 27

– IL-10 down regulates activity of macrophages – less NO, reactive oxygen intermediates etc and this switches off macrophage killing mechanisms
– IL-10 induces the release of TNFR-2 – and soluble TNFR-2 forms a complex with TNF-α and downregulates the TNF-α induced apoptosis of macrophages – causing survival of Mtb infected macrophages