5. Cell Recognition and the Immune System

Question 1

What is an antigen?

Answer 1

A cell-surface molecule that triggers an immune response which the immune system recognises as non-self (foreign)

Question 2

What is an antibody?

Answer 2

A protein with specific binding sites produced by B-cells in response to the presence of a specific antigen

Question 3

How are each type of cells identified?

Answer 3

By specific molecules on its surface that identify it

Question 4

What do cell-surface molecules enable the immune system to identify and when can this be an issue?

Answer 4

Pathogens, abnormal body cells, cells from other organisms of the same species and toxins (?)
This becomes an issue when a patient has tissue or organ transplants as the immune system will recognise these as ‘non-self’ (which is why matching takes place and immunosuppressants are given)

Question 5

What is the first line of defence?

Answer 5

Natural, physical and chemical barriers that aim to reduce the risk of bacteria/infection entering the body

Question 6

What is the second line of defence and describe the process

Answer 6

Phagocytosis

- The pathogen releases chemicals and has antigens which attracts the phagocytes.