4. Innate Immunity

Question 1

What is infectivity?

Answer 1

Ability of a microbe to establish itself within and on host

Question 2

What is virulence?

Answer 2

Capacity of pathogen to do damage in host cell

Question 3

What is the definition of the immune system?

Answer 3

Cells and organs that contribute to immune defences against infectious and non-infectious conditions (self vs non-self)

Question 4

What is the most important organ in the immune system?

Answer 4

Spleen

Question 5

What is the definition of an infectious disease?

Answer 5

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

Question 6

What are the roles of the immune system?

Answer 6

Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens

Question 7

What is innate immunity?

Answer 7

Natural immunity
Immediate protection
Fast, lack of specificity, lack of memory, no change in intensity

Question 8

What is adaptive immunity?

Answer 8

Long lasting 
Slow
Specificity
Immunological memory - gives stronger and faster immune response 
Changes in intensity

Question 9

What are the first lines of defence in the innate immunity?

Answer 9

Physical barriers
Physiological barriers
Chemical barriers
Biological barriers

Question 10

What are the physical innate barriers?

Answer 10

Skin
Mucous membranes
Bronchial cilia

Question 11

What are the physiological innate barriers?

Answer 11

Diarrhoea
Vomiting
Coughing
Sneezing

Question 12

What are the chemical innate barriers?

Answer 12

Low pH

Antimicrobial molecules

Question 13

What microbial barriers are involved in the chemical barriers?

Answer 13

IgA (tears, salvias mucous membrane) - prevents microbe attaching to host
Lysozyme (sebum, perspiration, urine)
Mucus - traps microbes
Beta-defensins (epithelium)
Gastric acid and pepsin

Question 14

What are the biological barriers?

Answer 14

Normal flora: non pathogenic microbes, strategic locations (nasopharynx, mouth/throat, skin, GI tract, vagina)

Question 15

What are the benefits of biological barriers?

Answer 15

Compete with pathogens for attachment sites and resources
Produce antimicrobial chemicals
Synthesise vitamins
Immune maturation

Question 16

What are some example of normal flora that inhabit the skin?

Answer 16

Staphylococcus aureus/epidermidis/pyogenes
Candida albicans
Clostridium perfringens

Question 17

What are examples of normal flora that inhabit the nasopharynx?

Answer 17

Streptococcus pneumoniae
Neisseria meningitis
Haemophilus species

Question 18

When do clinical problems start with normal flora?

Answer 18

When normal flora is displaced from its normal location to sterile location 
Breaching the skin integrity
Faecal-oral route
Faecal-perineal-urethral route 
Poor dental hygiene/dental work

Question 19

Who are the high risk patients for serious infections?

Answer 19

Asplenic and hyposplenic patients
Patients with damaged or prosthetic valves
Patients with previous infective endocarditis

Question 20

What are macrophages?

Answer 20

Present in all organs
Ingest and destroy microbes (phagocytosis)
Present microbial antigens to T cells
Produce cytokines/chemokines

Question 21

What are monocytes?

Answer 21

Recruited a infection site and differentiate into macrophages

Question 22

What are neutrophils?

Answer 22

Increased during infection
Recruited by chemokines to site of infection
Ingest and destroy pyogenic bacteria

Question 23

What are basophils/mast cells?

Answer 23

Early actors of inflammation (vasomodulation)

Importance in allergic responses

Question 24

What are eosinophils?

Answer 24

Defence against multi-cellular parasites

Question 25

What are natural killer cells?

Answer 25

Kill all abnormal host cells

Question 26

What are dendritic cells?

Answer 26

Present microbial antigens to T cells

Question 27

What microbial structures are involved in pathogen recognition?

Answer 27

Pathogen-associated molecular pathogens (PAMPs) | - carbohydrates, lipids, proteins, nucleic acids

Question 28

What are PRRs?

Answer 28

Pathogen recognition receptors on phagocytes

Question 29

What is opsonisation of microbes?

Answer 29

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

Question 30

Give examples of opsonins

Answer 30

Complement proteins: C3b, C4b Antibodies: IgG, IgM Active phase proteins: C-reactive protein, MBL

Question 31

What does the opsonins receptor do?

Answer 31

Signals phagocyte to engulf microbe

Question 32

Describe the process of phagocytosis

Answer 32

1. Chemotaxis and adherence of microbe to phagocyte 2. Ingestion of microbe by phagocyte 3. Formation of a phagosome 4. Fusion of phagosome with a lysosome to form phagolysosome 5 Digestion of ingested microbe by enzymes 6. Formation of residual body containing indigestible material 7. Discharge of waste materials

Question 33

What are the 2 phagocytes intracellular killing mechanisms?

Answer 33

Oxygen-dependent pathway (respiratory burst) - toxic O2 products for pathogens Oxygen-independen pathways - lysozyme, proteolytic and hydrologic enzymes

Question 34

What are the 2 activation pathways in the complement system?

Answer 34

Alternative pathway | MBL pathway

Question 35

When is alternative pathway initiated?

Answer 35

Initiated by cell surface microbial constituents (endotoxins)

Question 36

When is MBL pathway initiated?

Answer 36

Initiated when MBL binds to mannose containing residues of proteins found on many microbes

Question 37

What are the antimicrobial actions in the alternative pathway?

Answer 37

C3a and C5a: recruitment of phagocytes C3b-C4b: opsonisation of pathogens C5-C9: killing of pathogens, membrane attack complex

Question 38

What are cytokines and chemokines involved in?

Answer 38

Chemoattraction Phagocyte activation Inflammation

Question 39

What are the clinical problems when phagocytosis is reduced?

Answer 39

Decreased spleen function Decreased neutrophil number Decreased neutrophil function