C4

Question 1

Strategy that pathogen use to survive & reproduce

Answer 1

• Surviving colonisations
• Defending against complement
• Avoiding phagocytosis
• Survival inside phagocytes
• Immune evasion
• Resistance to antibiotics

Question 2

How pathogen survive colonisation

Answer 2

• Must multiply to colonise host
• Must compete with normal flora for nutrients & space
• IgA Abs against adhesion inhibit attachment of pathogens to mucosal surface & prevent subsequent infection

Question 3

Strategy to survive colonisation

Answer 3

• Rapid turnover of pili
• Antigenic variation
• IgA protease that cleave antibody molecule
• Produce siderophore

Question 4

Delivery of effector molecules to host cells

Answer 4

• Deliver certain molecules directly to host cell
• Eg: damage the cell, loss of microvilli, uptake bacterial cell

Question 5

Explain complement

Answer 5

• Heat labile component of normal plasma that enhance opsonisation of bacteria & allow antibody kill bacteria
• Activity said to complement the antibacterial activity of antibody

Question 6

Role of complement system

Answer 6

• Made up large number of distinct plasma protein that react with one another to opsonise pathogens
• Number of complement protein are over 30

Question 7

Mechanism to avoid killing by complement proteins

Answer 7

• Lysis of foreign cell by complement membrane attack complex (MAC)
• Opsonisation
• Inflammation

Question 8

Gram positive or Gram negative susceptible to MAC

Answer 8

Gram negative

Question 9

Define serum resistant

Answer 9

Gram negative bacteria that avoid killing by complement protein

Question 10

Some pathogen carry surface components such as

Answer 10

• Sialic acid that capture complement regulatory protein that cause inactivation of C3b alternate pathways of complement
• N. gonorrhoea

Question 11

Mechanism to avoid phagocytosis

Answer 11

• Prevent encounters with phagocytes (macrophages & neutrophils)
• Avoiding recognition & attachment
• Fc receptor

Question 12

Explain preventing encounter with phagocytes

Answer 12

• Avoid detection
• Killing phagocytic cell
• Include C5a peptidase to degrade C5a
• membrane damaging toxin

Question 13

What structure that are use to avoid recognition & attachment

Answer 13

• Capsule: interfere alternative pathways of complement activation
• M protein: similar functions of capsule

Question 14

Explain Fc receptor

Answer 14

• Protein found on surface of S.aureus (protein A) & S.pyogenes (Protein G)
• Stop opsonisation by antibody

Question 15

Mechanism use to survive inside phagocytes

Answer 15

• Escape from phagosome
• Preventing phago-lysosome fusion
• Surviving within the phagolysosome

Question 16

Mechanism of avoiding antibodies

Answer 16

• IgA protease: cleave IgA
• Antigenic variation: changes surface antigen
• Mimicking host molecules: cover themselves with molecule resembles normal molecules

Question 17

Explain the mechanism of avoiding antiviral effects of interferons (immune evasion)

Answer 17

• Encode certain protein that shut down translation in host
• Alter enzymatic activities in cell

Question 18

Explain the regulations of host cell death by virus (immune evasion)

Answer 18

• Kill the host cell after production large no of viral copies in order to spread to other cells
• Control immune surveillance to avoid premature death of their host
• Replicate rapidly induce apoptosis or programmed cell death of host to limit inflammatory response

Question 19

Mechanism of immune evasion

Answer 19

• Produce dsRNA intermediate to induce apoptosis
• Inhibit process of apoptosis by controlling p53 - associated with tumor development
• Block antigen presentation by MHC class I
• Cell not display MHC killed by natural killer cell

Question 20

Explain about antibodies & viruses (immune evasion)

Answer 20

• Directly transfer from one cell to its neighbours (Mareck disease virus)
• Remain intracellular by forcing all cellular neighbour to join commune called syncytium (HIV)
• Use antibody to enhance ability to infect cell (antibody mediated enhancement infection)
• Outpace body capacity by producing virus specific Abs by shifting antigen (psudospecies)

Question 21

Virus damages to the host (immune evasion)

Answer 21

• Lysis of cell
• Damage due to inflammatory response & destruction by virus & cytotoxic T cell
• Activation of apoptosis in host

Question 22

Explain immune evasion in fungi

Answer 22

• Cause lung diseases & granulomatous damage to lung
• Produce mycotoxins (A. flavus)
• Spores &fungal element cause hypersensitivity
• Dermatophytes cause superficial infection of hair, skin, nails

Question 23

Explain immune evasion in eukaryotic parasites

Answer 23

• Live in intestinal tract or enter body via antrophod
• Use variety mechanism to avoid antibody
• Hide within cell (RBC) - not present antigen

Question 24

Example of immune evasion by eukaryotic parasites

Answer 24

• P.vivax attach to Duffy blood group antigen
• Leishmania survive & multiply in macrophages
• African trypansome avoid antibody by routinely varying surface antigen

Question 25

Define antimicrobial, antibiotic & antifungal

Answer 25

Antimicrobial
- Drugs that treat many type of infection by killing or slowing the growth of pathogen

Antibiotic
- Treat bacterial infection

Antifungal
- Treat fungal infection

Question 26

Resistance mechanisms defense strategies

Answer 26

• Restrict access of antibiotics: Gram negative have outer layer membranes
• Rid of antibiotics or antifungal: P.aeruginosa produce pumps
• Change or destroy antibiotic: K.pneumonia produce enzyme
• Change target for antibiotics: E.coli code for mcr-1 gene
• Bypass the effects of antibiotics: S.aureus bypass trimethoprim