Defense Systems

Question 1

What are the roles of the immune system?

Answer 1

• Recognition > to detect invading pathogens (non-self)
• Reponse > to neutralise and destroy the invading pathogen
• Regulation > to ensure damage to ‘self’ is minimised.

Question 2

What are the two layers of the immune system?

Answer 2

• Innate immune system

- Adaptive immune system.

Question 3

Describe the response of innate (non-specific) immunity.

Answer 3

• Ready to go protection
• Broadly specific receptors
• Same response each time a pathogen is encountered but response differs for different pathogens.

Question 4

Give examples of physical barriers.

Answer 4

• Skin/shell
• Mucus
• Cilia - small hairs in throat and nostrils
• Lysozyme
• Acid in stomach and urine
• Commensals - Non-harmful bacteria, limit nutrients and space for harmful bacteria to grow.

Question 5

Give examples of internal innate defences.

Answer 5

• Fever
• Chemical signals
• Inflammation.

Question 6

What are phagocytes?

Answer 6

• White blood cells which ingest invaders

- types - neutrophils, macrophages

Question 7

What are neutrophils?

Answer 7

• Type of phagocytes
• Most abundant white blood cell
• Self-destruct after ingesting a pathogen
• Cell remains form pus.

Question 8

What are macrophages?

Answer 8

• Type of phagocyte
• Can be free types or fixed types
• Catches phagocytes with cytoplasmic extensions and engulfs
• Unlike neutrophils it can do this ver and over.

Question 9

What are natural killer cells?

Answer 9

• Type of lymphocyte
• Can kill your own cells if they have become infected with viruses or cancerous
• NK cells can detect this through the lack of MHC1 (Major Histocompatibility Complex).
• NK cells do not engulf defective cells, they use enzyme to initiate apoptosis.

Question 10

What is the inflammatory response?

Answer 10

• Body’s alaram
• Mast cells at the site release histamine - causes redness, heat and vasodilation at site
• Attracts phagocytes.

Question 11

What is a fever?

Answer 11

• When there are too many invaders for the phagocytes
• Phagocytes release pyrogen - which causes the pituitary gland to raise body temperature
• This increases metabolism of cells so they can heal faster.

Question 12

What is a B cell?

Answer 12

• Type of lymphocyte
• Determines foreign invaders from self
• Differentiates to form antibody producing cells (effector cells) and memory cells.

Question 13

What does a T cell do?

Answer 13

• Type of lymphocyte

- Kills virus infected cells and regulates activities of other white blood cells.

Question 14

What do plasma cells do?

Answer 14

• Type of lymphocyte

- Secrete antibodies.