Innate Immunity

Question 1

Three physical barriers in the innate immune system

Answer 1

Skin
Mucous Membrane in the mouth, resp tract, GI tract, Urinary tract
Bronchial cilia

Question 2

4 Physiological barriers to infection

Answer 2

Diarrhoea
Vomiting
Coughing
Sneezing

Question 3

2 Chemical barriers? (Note give examples 5)

Answer 3

Low pH (Eg. skin 5.5, stomach, vagina)

Antimicrobial molecules eg. IgA, Lysozyme, Mucus, Β-defensins, gastrci acid and pepsin

Question 4

What is the main biological barrier to infection? Where is it located?

Answer 4

Normal flora

Nasopharynx, mouth, throat, skin, GI tract, Vagina

Question 5

Benefits of the normal flora?

Answer 5

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

Question 6

4 reasons why someone may be immunocompromised?

Answer 6

Chemo
AIDS
Diabetes
Malignant diseases

Question 7

3 features of macrophages?

Answer 7

Phagocytosis
Professional antigen presenting cells
Produce cytokines

Question 8

What are monocytes?

Answer 8

Present in the blood, recruited at the site of infection and differentiate into macrophages

Question 9

what is a chemokine?

Answer 9

Chemokines are chemicals that are able to induce chemotaxis (Neutrophils move up the chemical gradient to the site of infection)

Question 10

Function of basophils and mast cells?

Answer 10

Early promoters of inflammation

Important in allergic responses

Question 11

Function of Eosinophils?

Answer 11

Defence against multi-cellular parasites

Question 12

Function of Natural killer cells

Answer 12

Kill abnormal host cells

Question 13

Function of dendritic cells?

Answer 13

Present antigens to T cells. Activate Adaptive immunity

Question 14

How does the macrophage recognise the bacteria?

Answer 14

Looks for Pathogen associated molecular patterns on the pathogen. These aren’t present on host cells PAMPs

Phagocytes have pathogen recognition receptor to recognise PAMPs (Eg. Toll like receptor)

Question 15

What is opsonisation?

Answer 15

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

Question 16

Give 3 types of opsonins

Answer 16

Complement proteins
Antibodies
Actue phase proteins

Question 17

Describe the process of phagocytosis and degradation of pathogens 6

Answer 17

1. Phagocyte chemotaxis to microbe, and adheres to it
2. Ingests microbe
3. Forms a phagosome
4. Lysosome fuses with the phagosome to form a phagolysosome
5. Enzymes digest ingested microbes
6. Discharge of waste materials

Question 18

What is the oxygen dependent pathway of killing in phagocytes? What is the oxygen independent pathway of killing?

Answer 18

Respiratory burst
Toxic oxygen products eg.Hydrogen peroxide, hydroxyl radical, Nitric oxide etc..

Lysozyme, lactoferrin or transferrin, cationic proteins, proteolytic and hydrolytic enzymes

Question 19

What are the two pathways for activating the complement system?

Answer 19

Alternative pathway- Initiated by cell surface microbial constituents (Eg. endotoxins)

MBL pathway (Mannose Binding Lectin)- MBL binds to mannose containing residues of proteins found on many microbes

Question 20

What are the actions of macrophage derivved TNFa, and interleukins
Organ then action

Answer 20

Liver: Release of opsonins eg. CRP and MBL (–>complement activation)
Bone marrow: Neutrophil mobilisation
Inflammatory actions: Vasodilation, cascular permeability and adhesion molecules–> attraction of neutrophils

Hypothalamus: Increased body temp

Question 21

What can you start to get problems with infections (Clinical conditions)? 3

Answer 21

Decreased spleen function
Decreased neutrophil number
Decreased neutrophil formation