Immune system

Question 1

antigen

Answer 1

specific surface marker on pathogens that can be detected by WBC

Question 2

self
non-self

Answer 2

surface marker detected as belonging to the human body
surface marker detected as being foreign to the human body

Question 3

what is the main function of the immune system and what are the 3 ways in which this is achieved?

Answer 3

Main function: Protect the body against infection by
- prevent entry of pathogens (1st line, innate)
- trap and destroy pathogens (2nd line, innate)
- destroy specific pathogens (3rd line, adaptive)

Question 4

describe 3 characteristics of non-specific/innate immunity (1st and 2nd line of defence)

Answer 4

• same response and level of response for all pathogens
• no memory of previous infections
• immediate response

Question 5

describe 4 characteristics of specific/adaptive immunity (3rd line of defence)

Answer 5

• different response and level of response for all pathogens
• memory of previous infections
• response to a new pathogen is delayed the - first time and faster the second time
• uses antibodies

Question 6

Process of inflammation

Answer 6

• first line of defence is penetrated
• Mast cells release histamine which causes vasodilation

> Leads to increased permeability of blood vessels causing plasma and WBC to leak out of capillaries.

> Build-up of tissue fluid causes swelling to trap pathogens + presses on nerve endings to cause pain, make us protect the area, preventing further entry of pathogens

Question 7

describe the process of phagocytosis

Answer 7

• phagocyte recognises pathogen as non-self
• phagocyte engulfs pathogen, forming a phagosome (vesicle around pathogen)
• phagosome fuses with lysosome which contains digestive enzymes to break down the pathogen, forming a phagolysosome
• after the pathogen is destroyed, unwanted debris is removed from the cell

Question 8

how does a fever contribute to the second line of defence?

Answer 8

increased temperature creates a hostile environment for bacteria, making it hard for them to survive and infect cells

Question 9

Describe the 3rd line of defence
(Adaptive/specific immune response)

Answer 9

• B and T cells are able to detect and recognise the specific antigens
• B - Plasma cells produce antibodies which can detect and destroy the specific antigen.
• Cytotoxic T cells release cytotoxins which kill the invading pathogen.
• Memory B and T cells remain in the circulation allowing for a faster and stronger
• response on secondary exposure to the same antigen, hence providing immunity against the disease.

Question 10

what is an autoimmune disease?

Answer 10

a condition in which antibodies are produced that mistakenly recognise self tissue as non-self and attack it e.g. coeliac disease