5.1 Defence Mechanisms

Question 1

What are the two responses involving a lymphocyte

Answer 1

1. Cellular response (Cell mediated response) involving T lymphocytes
2. Humoural response involving B lymphocytes

Question 2

Protein molecules on the cell membrane of molecules allow the immune system to identify

Answer 2

1. Pathogens, such as HIV
2. Non-self material such as cells from other organisms of the same species
3. Toxins including those produed by certain pathogens e.g. cholera
4. Abnormal body cells like cancer cells

Question 3

How do lymphocytes recognise cells belonging to the body

Answer 3

There are a large number of lymphocytes, in the fetus these are constantly colliding with other cells.

Lymphocytes will therefore only collide with self material, if lymphocytes have receptors that exactly fit those of the body’s own cells they will be killed or suppressed. The remaining lymphocytes will only fit foreign material.

Question 4

Examples of physical defence mechanisms

Answer 4

1. SKin
2. Earwax
3. Hairs (cillia)