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Communicable diseases - AQA The immune system in defence against disease

Pathogens are disease-causing viruses, bacteria, fungi or protists, which can infect animals and plants. Humans have an immune system, which can defend them from pathogens.

Part of Biology (Single Science)Infection and response

The immune system of the human body in defence against disease

If pass the non-specific first line of defence they will cause an infection. However, the body has a second line of defence to stop or minimise this infection. This is called the . As a part of this there are two types of white blood cell called and .

Phagocytes

A pathogen surrounding by a Phagocyte
Figure caption,
Phagocyte engulfing a bacterial cell

Phagocytes surround any pathogens in the blood and engulf them. They are attracted to pathogens and bind to them.

The phagocytes membrane surrounds the pathogen and enzymes found inside the cell break down the pathogen in order to destroy it. As phagocytes do this to all pathogens that they encounter, they are called 'non-specific'.

Lymphocytes

A lymphocyte
Figure caption,
A medical illustration of a lymphocyte

Lymphocytes are another type of white blood cell. They recognise proteins on the surface of pathogens called . Lymphocytes detect that these are foreign not naturally occurring within your body and produce . This can take a few days, during which time you may feel ill. The antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them.

Some pathogens produce which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins. Both the antibodies and antitoxins are highly specific to the antigen on the pathogen, thus the lymphocytes that produce them are called 'specific'.