Innate Immunity

Question 1

What are the three phases of response to initial infection? when do they occur?

Answer 1

Innate Immunity; this occurs immediately (0-4hrs) as components are already formed.
Early induced response; Early (4-96hrs) involves the recruitment of cells
Adaptive immune response (96+hrs) involves making new immune cells and antibodies

Question 2

What are some mucosal surfaces where pathogens can enter?

Answer 2

Airway, GI tract and Gu

Question 3

Name a pathogen that enters via the airway and what disease it causes?

Answer 3

Influenza Virus causing influenza

Question 4

Name a pathogen that enters the GI tract and what disease it causes?

Answer 4

Salmonella causing typhoid fever

Question 5

Name a pathogen that enters through the GU and what disease it causes?

Answer 5

Treponoma Pallidum causing syphilis

Question 6

Name the ways in which pathogens can enter through external epithelia

Answer 6

External surface, wounds and abrasions, and insects bites

Question 7

Name a pathogen that enters through external surface of epithelium and the disease it causes?

Answer 7

Tinea Pedis causing Athlete’s foot

Question 8

Name a pathogen that enters through wounds and abrasions and the disease it causes

Answer 8

Clostridium tetani causing tetanus

Question 9

Name a pathogen that enters via inset bites and the disease it causes

Answer 9

Plasmodium causing malaria

Question 10

What are the different barriers to infection and name some specific examples

Answer 10

Mechanical - movement of cilia and tight junctions between cells
Chemical - Fatty acids on skin & Stomach acid.
Microbiological - Normal flora to compete for nutrients and attachment

Question 11

One pathogen crosses epithelial barrier what occurs? And what is this enhanced by?

Answer 11

It is recognised and ingested by mono-nuclear phagocytes or macrophages. This is enhanced by the presence of receptor on the phagocytic cell that can recognise pathogens

Question 12

Name some of the bacericidal effects and agents produced by phagocytes

Answer 12

• Acidification (acidic environment)
• Toxic oxygen derived products
• Toxic nitrogen oxides
• Peptides (defensins)
• Enzymes (lysosmye)
• Competitors (lactoferrin)

Question 13

All cells of the immune system are derived from what?

Answer 13

Haemotopoeitic stem cell

Question 14

What is key about the circulation time of neutrophils

Answer 14

They only circulate for 12 hours. So if a drug or agent is affecting the immune system this is first seen here.

Question 15

What do mast cells release?

Answer 15

Substances that effect vascular substances. They are full of histamine

Question 16

What is the function of B and T cells

Answer 16

B cells - Production of antibodies

T cells - Become cytotoxic T cells (CD8) or helper T cells (CD4)

Question 17

What are neutrophils, basophils and eosinophils involved in?

Answer 17

Neutrophil - Ingest bacteria
Eosinophil - Important in parasite defence
Basophils - Involved in hypersensitivity reactions

Question 18

What is the role of natural killer cells and dendritic cells?

Answer 18

Natural Killer - Recognise virally infected cells

Dendritic cells - Bridges innate and adaptive immune responses (antigen presenting cells)

Question 19

What do virally infected cells release?

Answer 19

Interferon alpha (IFN-α) and Interferon Beta (IFN-β)

Question 20

What does the release of IFN-β and IFN-α cause?

Answer 20

Near by cells to become slightly more resistant to the virus, upregulates a class of proteins called MHC class 1 and finally activates other natural killer cells.

Question 21

Describe what Natural Killers cells interact with and what happens when the cell is infected?

Answer 21

They interact with MHC class 1 receptors on healthy cells and this stops the NK from killing it. However when a cell is infected with a virus it no longer produced MHC class 1 receptors so the NK cannot interact and therefore it kills the cell

Question 22

What are two of the main complement pathways and what activates them?

Answer 22

Classical Pathway - Antibody binds to specific antigen on pathogen surface
Alternative Pathway - Pathogen surface creates local environment which triggers complement activation

Question 23

What are some of the outcomes for the complement system?

Answer 23

• Recruitment of cells
• Opsonization of pathogens
• Lysis and death of pathogens

Question 24

Name an example of an opsonin

Answer 24

C3b

Question 25

Name two examples of mediators of inflammation

Answer 25

C5a and C3a

Question 26

What is the classical pathway initiated by?

Answer 26

Activation of the c1 complex which binds to antigens on the pathogen surface.

Question 27

What occurs tp C3 in the complement cascade?

Answer 27

It is cleaved into C3b which sticks to the cell acting as an opsonin and C3a floats away and recruits more cells.

Question 28

What is the alternative pathway caused by?

Answer 28

The spontaneous hydrolysis of serum C3. C3b then binds to pathogen surface creating that environment which triggers the alternative pathway.

Question 29

What forms the membrane attack complex (MAC) and what does it do

Answer 29

It is formed from complement serum proteins; C6, C7, C8, and C9 and it punches wholes in the surface of pathogens causing it to die

Question 30

What is the function of CD59?

Answer 30

It prevents membrane attack complexes from forming on the surface of host cells. SO it is there for protection

Question 31

Name some examples that inhibit the complement system and why this is needed

Answer 31

DAF, MCP and Cr1. This is to prevent immune responses when they are not needed.

Question 32

Patients with complement Deficiencies often present with what?

Answer 32

Recurring bacterial infections which differ depending on which complement serum protein they are deficient in.