3.6 Immune Evasion

Question 1

Innate immune response is efficient in

Answer 1

Providing immediate and broad spectrum protection against a wide range of pathogens

Question 2

How does innate immune response provide broad protection

Answer 2

Recognises common features of various pathogens such as bacterial cell wall, components via nuclei acid components or fungal wall components

Question 3

When do bacteria have opportunity to cause infection

Answer 3

Impairment of body’s ability to recognise respond to and eliminate infections

Question 4

Impaired innate immunity can be due to

Answer 4

Deficiency in complement proteins

Deficiency in antibodies

Neutropenia

Question 5

What is immune evasion

Answer 5

Critical strategy for pathogens to successfuly infect and persist within their host

Question 6

Keyb srategies of immune evasion

Answer 6

Avoid recognition

Inhibit phagocytosis

Kill immune cells

Survive inside cells

Disrupt immune signalling

Mimic host molecules

Question 7

Complement strategies of immune evasion

Answer 7

Avoid recognition and inhibit ohagocytosis

Question 8

Antibody strategies of immune evasion

Answer 8

Avoid recognition and inhibit ohagocytosis

Question 9

Phagocytes strategies of immune evasion

Answer 9

Kill Immune cells

Question 10

Infection of s aureus can be

Answer 10

Community or hospital aquired

Question 11

What is s aureus

Answer 11

Gram positive bacterium that can live harmlessly in the skin of humans but is an opportunistic pathogen able to cause range of diseases

Question 12

MRSA

Answer 12

Difficulty in treating due to AB resistance

Commonly hospital acquired

Question 13

Superficial infections of MRSA

Answer 13

Skin and soft tissue infections

Bactaeremia and sepsis

Question 14

Invasive infections of MRSA

Answer 14

Osteomyelitis

Endocarditis

Question 15

How does s aureus evade complement response

Answer 15

Degrades c3

Inhibits formation of c3 convertase (inhibit c1)

Inhibits c3 and c5 convertase

Inhibits c5

Question 16

S aureus degrading c3

Answer 16

Protease Aur degrades c3 preventing c3b deposition adn c3b formation

Question 17

S aureus inhibits formation of c3 convertase

Answer 17

Sbi protein binds to IgG preventing recognition by c1

Prevents formation of c3 convertase in the classical pathway

Question 18

S aureus inhibits c3 and 5 convertase

Answer 18

SCIN proteins bind to c3bBb in alternative pathway preventing c3 and c5 convertase

Question 19

S aureus inhibits c5

Answer 19

Ssl7 protein binds c5 preventing formation of c5 convertase

Question 20

Summary of s aureus evading complement responses

Answer 20

Disrupt complement functions

Prevent complement opsonisation

Allowing escape from complement mediated phagocytosis and killing

Question 21

How does s aureus evade antibody responses

Answer 21

Express capsule polysaccharides

Express surface molecules that bind to antibodies non-opsonically

Digest or modify antibodies

Release molecules to block Fc eceptors

Question 22

S aureus capsule polysaccharide hides antigens

Answer 22

Bacteria expresses capsule on their surface to hide antigens being detected by antibodies

Question 23

S aureus in expressing surfwce molecules that bind antibodies non opsonically

Answer 23

Express protein a which bind Fc portion of antibodies instead of their fab region preventing opsonisation

Question 24

S aureus in causing proteolytic cleavage of antibodies

Answer 24

Proteases cleave or modify antibodies preventing opsonisation

Question 25

S aureus releasing molecules which bind and block Fc receptors

Answer 25

Proteases cleave or modify antibodies preventing opsonisation

Question 26

Summary of s aureus evading antibodies

Answer 26

Hide antigens
Disrupt antibody function
Prevent antibody detection

Question 27

How do s aureus kill phagocytes

Answer 27

Expression of toxins

Question 28

S aureus expression of toxins

Answer 28

Release toxins to kill immune cells to inhibit phagocytosis