Immune system: second line of defence

If pathogens pass the non-specific first line of defence, they will cause an infection.

the body has a second line of defence to stop or minimise this infection. This is called the immune system

the immune system mainly consists of two types of white blood cell called phagocytes and lymphocytes

Phagocytes are attracted to pathogens in the blood and bind to them. The phagocyte’s membrane surrounds the pathogen and engulfs it.

Enzymes found inside the cell then 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 are another type of white blood cell. They recognise proteins on the surface of pathogens called antigens.

Lymphocytes detect that these are foreign, which are not naturally occurring within the body, and produce antibodies.

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 toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins.

sometimes our immune system does not work right and might destroy normal helpful cells which can cause type 1 diabetes or bad eyesight