Lecture 7- Immune evasion

Question 1

different roles of adaptive and innate immunity

Answer 1

innate more for fast pathogens and early response, adaptive can become important for limiting growth and initiating clearance

Question 2

examples of innate responses to salmonella

Answer 2

complement, enterocytes producing defensins, changes in mucus production

Question 3

example of a parasite and a specific immune response related to it

Answer 3

nematodes- Th2 mediates explusion, mast cells, IgE important
also see changes in mucus and gut motility

Question 4

6 evasion strategies

Answer 4

speed
inhibition
avoid detection
change rapidly
spoke-screen effects
‘wrong response’

Question 5

speed- example

Answer 5

colds and flu, replicate quickly and spread before adaptive immunity can kick in

Question 6

inhibition- example

Answer 6

cytomegalovirus- uses a ‘decoy receptor’ to prevent chemokine action
HIV can reduce levels of MHC I on the surface of cells, inhibiting responses from Th/NK cells etc

Question 7

avoiding detection- example

Answer 7

plasmodium- using RBCs, which lack MHC
papilloma virus- replication only at outer skin layers, which have less strong immune detection mechanisms

Question 8

rapid change- example

Answer 8

influenza- antigenic variation, has 8 RNA segments making up its antigen and these can change (recomb., point mutations etc)
covid- variants, idea of ‘escape variants’
can also happen in parasites within a host- trypanosome surface glycoproteins

Question 9

what are smoke-screen effects

Answer 9

causing a response to a non-protective antigen/part of the pathogen

Question 10

smoke-screen effects- example

Answer 10

N. meningitidis, can create a large volume of T cells against non-protective antigens
non-specific activation of the immune system can be induced

Question 11

‘wrong response’ examples

Answer 11

virokine production- secreted from host cells to create a better environment for host infection

Question 12

example of an impact on the complement system

Answer 12

pseudomonas- inactivation of C3b and C5a, prevents recruitment of innate immune cells

Question 13

how can bacteria prevent phagocytosis

Answer 13

‘slippery’ capsules, and shedding the surface antibodies quickly- e.g. S. pneumonia

Question 14

example of how cross-species events can lead to pathology

Answer 14

adaptation to oriignal host, e.g. covid-2- bats have high IFN but low PRR response, so covid interferes w IFN but less PRR- leads to greater inflammation