C1. Antigens

Question 1

What are antigens?

Antigen definition?
Where are they found?
What are foreign antigens?

Answer 1

Antigens are proteins that can generate an immune response when detected by the body. They are usually found on the surface of cells, including all your body cells. Antigens that aren’t normally found in the body are referred to as foreign antigens - it’s these antigens that the immune system usually responds to.

Question 2

Antigens allow the immune system to identify: (4 things. 2,1,2,2 points)

Answer 2

Pathogens

• organisms that cause disease, e.g. bacteria, viruses and fungi.
• All pathogens have antigens on their surface - these are identified as foreign by immune system cells, which then respond to destroy the pathogen.

Abnormal body cells

• Cancerous or pathogen - infected cells have abnormal antigens on their surface, which trigger an immune response.

Toxins

• poisons that are molecules, not cells.
• Some toxins are produced by bacteria
• The immune system can respond to toxins, as well as the pathogens that release them.

Cells from other individuals of the same species

• When you receive cells from another person those cells will have some antigens that are different to your own
• The foreign antigens trigger an immune response. This response leads to the rejection of transplanted organs if drugs aren’t taken to suppress the recipient’s immune system.