S2L2 - Innate Immune System

Question 1

What factors determine the outcome of the host pathogen relationship?

Answer 1

Infectivity of pathogen - how frequently a pathogen spreads horizontally.
Virulence - a pathogens ability to infect host cells.
Hosts immune response - if the hosts immune response is compromised, weakened (pregnant, infant, elderly) or impaired then they are likely to have worse outcomes.

Question 2

What is the immune system?

Answer 2

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

Question 3

What is an infectious disease?

Answer 3

When the pathogen succeeds in evading and/or overwhelming the hosts immune defences.

Question 4

Describe the roles of the immune system

Answer 4

Pathogen recognition= knowing the enemy. Cell surface and soluble receptors

Containing/eliminating the infection = killing and clearance mechanisms. Make sure that the pathogen doesn’t spread and become septic.

Regulating itself = minimum damage to host (resolution). Autoimmune diseases occurs when immune response is not regulated.

Remembering pathogen = preventing the disease from recurring on second contact.

Question 5

What is the difference between innate and adaptive immunity?

Answer 5

Innate immunity is the first line of defence providing immediate protection. It is fast/immediate, but has lack of specificity attacking all pathogens in the same way. It has a lack of memory and will always produce the same reaction with no change in intensity. Includes primary innate immunity (barriers) and secondary (immune cells)

Adaptive immunity is a second response. Provides long lasting protection. Is slow and may take days to start working. Has specificity. Has immunologic memory (b and T cells). Varies in intensity.

Question 6

What are the 4 innate immune barriers

Answer 6

Physical barriers
Physiological barriers
Chemical barriers
Biological barriers

Question 7

Describe the physical barriers of the innate immune system

Answer 7

Skin 
Mucous membranes (mouth, respiratory tract, GI tract, urinary tract - all have own lymphatic system so can produce adaptive response)
Bronchial cilia ( function impaired by cystic fibrosis, resulting in respiratory disorders.

Question 8

What are the physiological barriers of the innate immune system?

Answer 8

Get pathogens out of body!

Diarrhoea
Vomiting
Coughing
Sneezing

Question 9

What are the chemical barriers of the innate immune system?

Answer 9

Low pH - unfavourable environment for pathogens

• Skin (5.5)
• stomach (1-3)
• vagina ( 4.4 kept low by lactobacillus)

Antimicrobial molecules

• IgA
• Lysozomes
• Mucus
• Beta-defensins
• gastric acid + pepsin (keeps pH low)