Immune System

Question 1

How does the body identify self and non-self cells?

Answer 1

• lymphocytes identify the presence of pathogens and potentially harmful foreign substances in the body + destroy/ neutralise them to prevent harm

Question 2

How do lymphocytes distinguish between self cells/ pathogens?

Answer 2

• cells have specific molecules (antigens) on surface for identification

Question 3

What are the 4 things lymphocytes are able to identify?

Answer 3

• pathogens
• cells from other organisms of the same species (harmful for those with organ transplants)
• abnormal body cells (cancer)
• toxins (eg cholera)

Question 4

What is an antigen?

Answer 4

• a molecule that triggers an immune response by lymphocyte cells when detected in the body
• usually proteins located on the surface of cells

Question 5

What is meant by antigen variablity?

Answer 5

• DNA can mutate fre quently
• mutation in gene which codes for antigen changes shape of the antigen
• this means that any previous immunity (natural/ artificial) is no longer effective because all memory cells in the blood will have a memory of the old antigen shape

Question 6

How is an immune response triggered?

Answer 6

• if a pathogen gets past chemical/ physical barriers (eg skin/ stomach acid) and enters the blood, the WBC are second line of defense

Question 7

What are the specific and non-specific response for a WBC?

Answer 7

• specific : lymphocytes
• non-specific : phagocytosis