Grade Saved


Your grade

The immune system





The immune system prevents, detects and stops infection within the organisms

The immune system has many parts:

- Lymphocytes

- Antibodies

- Phagocytes [1]

Together they kill the pathogens which invade the body or organisms.


Antibodies attach to antigens.

Antigens are substances found on the surface of cells, including bacteria and other pathogens.

Different antibodies attach to different antigens.

In this way, the body’s immune system can recognise foreign antigens

– antigens that are not normally produced by the body, but by pathogens instead [3]


- Microorganism that causes disease. [5]


About 70% of the white blood cells are phagocytes.

They are part of the body’s immune system, but they do not produce antibodies.

Process of ingesting the pathogen

1. the phagocyte surrounds the bacterial cell, enclosing it in a vacuole

2. enzymes are secreted into the vacuole to destroy the bacterial cell

The process of ingesting the pathogen is called phagocytosis. [7]










- about 25% of the white blood cells are lymphocytes

- they are part of the body’s immune system and produce soluble proteins called antibodies

Lymphocytes carry antibodies that can recognise particular types of pathogen [2]


Antibodies attach to antigens.

Antibodies can neutralise toxins produced by pathogens.

They can also cause the destruction of pathogens by:

- causing bacteria to burst open and die

- labelling the pathogen so that it is recognised more easily by phagocytes

- sticking pathogens together in clumps so that they can be engulfed by phagocytes more easily [4]


- process of ingesting the pathogen [6]

BBC Bitesize - Blood


You may be interested in

© 2017