Cells: Cell Recognition & the Immune System - Antigens

Question 1

What are antigens?

Answer 1

• Antigens are molecules (usually proteins) that stimulate an immune response when detected by the body
• Found on the surface of cells

Question 2

Which types of antigens produce an immune response?

Answer 2

(Antigens from)

• Pathogens
• Abnormal body cells
• Toxins
• Cells from other organisms of the same species

Question 3

What are pathogens?

Answer 3

• Pathogens are organisms that cause disease e.g bacteria, viruses and fungi
• All pathogens have antigens on their surface
• These are identified as foreign antigens

Question 4

What are abnormal body cells?

Answer 4

• Cancerous or pathogen-infected cells have abnormal antigens on their surface

Question 5

What are toxins?

Answer 5

• Poisons - they’re molecules, not cells
• Some toxins are produced by bacteria
• Immune system can respond to toxins and the pathogens that release them

Question 6

Why do cells from other individuals of the same species trigger an immune response?

Answer 6

• Cells from another person have some antigens that are different from your own
• The foreign antigen triggers an immune response

Question 7

What are foreign antigens?

Answer 7

• Foreign antigens are antigens that aren’t normally found in the body
• The immune body responds to foreign antigens