Session 3-Innate Immunity

Question 1

Define immune system

Answer 1

Cells and organs that contribute to immune defences against infectious and non-infectious conditions

Question 2

What is an infectious disease?

Answer 2

When the pathogen succeeds in evading and/or overwhelming the host’s immune defences

Question 3

What are the roles of the immune system? (4)

Answer 3

1) pathogen recognition
2) containing/eliminating infection
3) regulating itself
4) remembering pathogens

Question 4

True or false: innate immunity provides long lasting protection

Answer 4

FALSE - immediate protection

Question 5

What are the innate physical barriers?

Answer 5

1) skin
2) mucous membranes
3) bronchial cilia

Question 6

What are the innate physiological barriers and what are they barriers against?

Answer 6

1) diarrhoea - food poisoning
2) vomiting - food poisoning, hepatitis, meningitis
3) coughing - pneumonia
4) sneezing - sinusitis

Question 7

What are the innate chemical barriers?

Answer 7

1) low pH

2) antimicrobial molecules

Question 8

What is the pH of skin?

Answer 8

5.5

Question 9

What is the pH of the vagina?

Answer 9

4.4

Question 10

What are normal flora?

Answer 10

Biological barrier, non-pathogenic microbes in strategic locations

Question 11

True or false: normal flora is present in internal organs/tissues

Answer 11

FALSE - absent

Question 12

Where are normal flora present?

Answer 12

Nasopharynx 
Mouth/throat
Skin
GI tract
Vagina

Question 13

What are the benefits of normal flora? (3)

Answer 13

1) Compete with pathogens for attachment sites and resources
2) Produce antimicrobial chemicals
3) Synthesise vitamins

Question 14

Which normal flora inhabits the skin?

Answer 14

Staphylococcus aureus

Question 15

Which normal florae inhabit the nasopharynx?

Answer 15

Streptococcus pneumoniae

Neisseria meningitidis

Question 16

When do clinical problems start with normal flora? (3)

Answer 16

1) when normal flora is displaced from its normal location to a sterile location
2) when normal flora overgrows and becomes pathogenic when the host becomes immuno-compromised
3) when normal flora is depleted by antibiotics

Question 17

In which ways can normal flora be displaced from its normal location? (3)

Answer 17

1) breaching skin integrity through burns, surgery, injections etc
2) fecal-oral route (foodborne)
3) fecal-perineal-urethral route (UTI)

Question 18

Which microbe causes vaginal thrush?

Answer 18

Candida albicans

Question 19

What are the three main types of phagocytes?

Answer 19

1) macrophages
2) monocytes
3) neutrophils

Question 20

Which phagocyte is present in pus?

Answer 20

Neutrophils

Question 21

What are the function of macrophages? (3)

Answer 21

1) phagocytosis
2) present microbial antigens to T cells
3) produce cytokines/chemokines

Question 22

What do monocytes differentiate into?

Answer 22

Macrophages

Question 23

When is the level of neutrophils increased?

Answer 23

During infection

Question 24

What is the function of neutrophils?

Answer 24

Ingest and destroy pyogenic bacteria

Question 25

Which other key cells are involved in innate immunity? (4)

Answer 25

1) basophils/mast cells 2) eosinophils 3) natural killer cells 4) dendritic cells

Question 26

Complete the sentence: Microbial structures have PAMPs (_________-_____________ __________ __________) which are recognised by PRRs (________ _____________ __________) on phagocytes.

Answer 26

Pathogen-associated molecular patterns | Pathogen recognition receptors

Question 27

Why are PRRs present inside the cell as well as on the surface?

Answer 27

Viruses replicate inside cells so to recognise viruses

Question 28

How does opsonisation of microbes take place?

Answer 28

Coating proteins called opsonins bind to microbial surfaces, leading to enhanced attachment of phagocytes and clearance of microbes

Question 29

Give examples of opsonins

Answer 29

1) Complement proteins eg C3b 2) Antibodies eg IgG 3) Acute phase proteins eg CRP and mannose-binding lectin (MBL)

Question 30

What are the two activating pathways of the complement system and what are they initiated by?

Answer 30

1) alternative pathway-initiated by cell surface microbial constituents 2) Mannose-binding lectin pathway-initiated when MBL binds to mannose containing residues of proteins found on microbes

Question 31

What are the antimicrobial actions of C3a and C5a complement proteins?

Answer 31

Recruitment of phagocytes (chemoattractants)

Question 32

What are the antimicrobial actions of C3b-C4b?

Answer 32

Opsonisation of pathogens

Question 33

What are the antimicrobial actions of C5-C9?

Answer 33

1) Killing of pathogens | 2) Membrane attack complex (form pores which punch holes in bacterial cell wall and kill bacteria)

Question 34

What is released by activated macrophages?

Answer 34

Tumour necrosis factor (TNFa) | Interleukins (IL-1/IL-6)

Question 35

What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the liver?

Answer 35

CRP | Mannose binding lectin -> complement activation

Question 36

What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in bone marrow?

Answer 36

Neutrophil mobilisation

Question 37

What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the inflammatory response?

Answer 37

Vasodilation Vascular permeability Adhesion molecules -> attraction of neutrophils

Question 38

What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the hypothalamus?

Answer 38

Increased body temperature

Question 39

Which clinical problems start with reduced phagocytosis?

Answer 39

1) Decreased spleen function 2) Decreased neutrophil number 3) Decreased neutrophil function