Innate Immunity

Question 1

What are the differences between innate and adaptive immunity?

Answer 1

Innate - fast (secs), lacks specificity, no memory, no change in intensity
Adaptive - slow (days),specificity, immunological memory, changes in intensity

Question 2

What are the first lines of defence within innate immunity?

Answer 2

Physical barriers
Physiological barriers
Chemical barriers
Biological barriers

Question 3

What are physical barriers in innate immunity?

Answer 3

Skin
Mucous membranes - mouth, resp tract, etc
Bronchial cilia

Question 4

What are physiological barriers in innate immunity?

Answer 4

Vomiting
Diarrhoea
Coughing
Sneezing

Question 5

What are chemical barriers in innate immunity?

Answer 5

Low pH - skin (5.5), stomach (1-3), vagina (4.4)

Antimicrobial molecules - igA (saliva and tears), lysozyme, mucus

Question 6

What are biological barriers in the innate immune system?

Answer 6

Normal flora in strategic locations - entry points

- nasopharynx, mouth/throat, skin, GI tract, vagina

Question 7

What are the benefits of normal flora within the body?

Answer 7

• Compete with pathogens for attachment sites and resources
• product antimicrobial chemicals
• synthesise vitamins - K, B12

Question 8

What normal flora is present in the nasopharynx?

Answer 8

Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species

Question 9

What normal flora is present on the skin?

Answer 9

Gram positive - staph aureus, staph epidermiditis, strep pyogenes

Question 10

When might normal flora become pathological?

Answer 10

1. Displaced from its normal location
2. Overgrows if host immunocompromised
3. Overgrows when normal flora depleted by antibiotics

Question 11

Give examples of infections that may be caused from displaced microflora?

Answer 11

UTI - E.coli from the colon enters the urethra

Cellulitis - Staph.aureus enters through a break in the skin

Question 12

Give 2 examples of infections that occur due to normal flora being depleted by antibiotics?

Answer 12

Clostridium difficile - severe colitis

Candida albicans - vaginal thrush

Question 13

Patients may be immunocompromised if…

Answer 13

Asplenic or hyposplenic 
Diabetic
AIDS
Malignant diseases 
Chemotherapy

Question 14

What are the second lines of defence within innate immunity?

Answer 14

Phagocytes, complement system, cytokines

Question 15

What is the result of activation of the second line of defence?

Answer 15

Inflammation

Question 16

What are the 3 main phagocytes in innate immunity?

Answer 16

Macrophages
Monocytes
Neutrophils

Question 17

Give examples of PAMPS on gram negative bacteria.

Answer 17

LPS

Lipoproteins and lipopeptides

Question 18

Give examples of PAMPS on gram positive bacteria.

Answer 18

Peptidoglycan

Lipoteichoic acids

Question 19

What is an example of a PRR?

Answer 19

Toll-like receptor

Question 20

What molecules act as opsonins?

Answer 20

• Complement proteins - C3b
• Antibodies - igG
• Acute phase proteins - CRP, MBL (mannose-binding lectin)

Question 21

Why are asplenic patients particularly vulnerable to encapsulated bacteria?

Answer 21

These bacteria require opsonisation in order to clear, patients without a spleen have reduced opsonisation.

Question 22

Give examples of 3 encapsulated bacteria that asplenic patients are at high risk of infection with.

Answer 22

Neisseria meningitis
Strep. Pneumoniae
Haemophilus influenzae

Question 23

What are the 2 phagocyte killing mechanisms, how do they differ?

Answer 23

Oxygen-dependent pathway (respiratory burst)
= Release of toxic oxygen products - superoxide, H202, hydroxyl radicals.

Oxygen- independent pathway
= proteolytic and hydrolytic enzymes

Question 24

What are the 2 activating pathways of the complement system?

Answer 24

1. MBL - initiated with MBL binds to mannose containing residues on proteins found on microbes
2. Alternative - initiated by cell surface microbial constituents (endotoxins on e.coli)

Question 25

What is the function of C3a and C5a?

Answer 25

Chemoattractants - recruit phagocytes

Question 26

What is the function of C3b and C5b?

Answer 26

Opsonisation of pathogens

Question 27

What is the function of C5-9?

Answer 27

Formation of membrane-attack complex (MAC)

Question 28

Which cytokines are released by macrophages/monocytes?

Answer 28

IL-1
IL-6
TNF-alpha

Question 29

What effects do IL-1,IL-6 and TNF-alpha have on the liver?

Answer 29

Synthesis and release of opsonins - CRP and MBL

Question 30

What effects do IL-1,IL-6 and TNF-alpha have on the bone marrow?

Answer 30

Neutrophil mobilisation

Question 31

How does infection result in an increased temperature?

Answer 31

Macrophage released IL-1, IL-6 and TNF alpha are pyrogens, and signal to the hypothalamus to increase body temperature

Question 32

What effects do IL-1,IL-6 and TNF-alpha have on the vasculature?

Answer 32

Vasodilation

Vascular permeability

Question 33

Which patients are likely to have reduced phagocytosis?

Answer 33

1. Decreased spleen function
2. Decreased neutrophil number - cancer chemotherapy, leukaemia/lymphoma, certain drugs (phenytoin)
3. Decreased neutrophil function

Question 34

Which diseases are associated with decreased neutrophil function?

Answer 34

Chronic granulomatous disease (no respiratory burst due to defective NADPH oxidase)

Question 35

What effect do corticosteroids have on the immune system?

Answer 35

Immunosuppressants