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They key points covered in this video include:
1. The Immune System
2. Phagocytosis
3. Antibody Production
4. Antitoxin Production

The Immune System

There are times when the body's non-specific defence mechanisms are not enough to stop pathogens from entering the body. In this case, the immune system gets activated to try and destroy pathogens that have made it through. White blood cells are a vital part of the immune system that help defend against pathogens. They are carried in the blood where they patrol for pathogens. If they detect the presence of a pathogen, they can respond in several ways.

Phagocytosis

Some types of white blood cells (called phagocytes) can engulf pathogens and then digest them - this is called phagocytosis. It is a non-specific response - i.e. a white blood cell can engulf any pathogen.

Antibody Production

Pathogens have unique marker proteins (antigens) on their cell surface. These can be recognised as 'foreign' by cells of the immune system, leading to a response that is specific to that pathogen. These antigens cause types of white blood cells called B-lymphocytes to produce proteins called antibodies. These bind, or lock onto, pathogens so they can be found and destroyed by other white blood cells. There are several different types of antibody - each binds only to one type of antigen, therefore to one type of pathogen. A single type of B-lymphocyte only produces one type of antibody. This means the response (the antibody produced) is specific to that particular type of invading cell.

Antitoxin Production

Another thing that white blood cells can do to prevent disease is produce antitoxins. These neutralise the toxins produced by bacteria.

Summary

1. The immune system is responsible for destroying pathogens that get into the body past the non-specific defence mechanisms
2. White blood cells play a key roles in this response
3. They patrol the blood for pathogens and identify them as 'foreign'
4. If their presence is detected they can:
a. Phagocytose pathogens - i.e. engulf and digest them
b. Produce antibodies which specifically bind to that particular type of pathogen, making it easier for them to be found and destroyed by other white blood cells
c. Produce antitoxins which neutralise toxins produced by bacteria

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