CHap 16- Avoiding host defenses

Question 1

Ways pathogens avoid host defenses?

Answer 1

hide within host cells, prevent encounters with phagocytes, avoid attachment & recognition, surviving within phagolysosomes

Question 2

If pathogen hides in host cells, it

Answer 2

avoids complement proteins, phagocytes and antibodies

Question 3

how do they Prevent encounters with phagocytes ?

Answer 3

avoiding macrophages and nphils all together. C5a PEPSIDASE (enzyme that degrades chemotractant that recruits phagocytic cells; MEMBRANE DAMAGING TOXINS-kills phagocytes & other cells

Question 4

How do they avoid recognition and attachment?

Answer 4

these things INTERFERE with OPSONIZATION; capsules & M proteins- binds hosts regulatory proteins that INACTIVATE with C3b; Fc receptors- bind Fc regions of antibodies

Question 5

When bacteria makes no attempt to be engulfed, it instead ____________ and does what to immune response?

Answer 5

hides from antibodies; take control of immune response to then be transported to other parts of body

Question 6

How do they survive within lysosomes?

Answer 6

1. Escape from phagosome before it fuses with lysosome
2. preventing phagosome-lysosome fusion avoiding exposure to lysosome
3. survive w/n phagolysosome (which very few bacs can do)

Question 7

How do they avoid killing by complement system?

Answer 7

be serum resistant- bacteria that have mechanisms to avoid the killing effect of complement system proteins; binds regulatory proteins to avoid MACs; gram neg bact is more susceptible to MACs