Summary of the immune system

Immunity is the body’s resistance to, and ability to fight off, illness. Fully innate immunity is the body’s first line of natural defence, including skin barriers, mucous membranes, cilia, mucous, stomach acid, Phagocytes and Natural Killer cells. It is also known as the non-specific immune system, meaning that the cells respond to pathogens in a general manner, rather than summoning memory cells or developing immunity to the pathogen. This type of immunity provides immediate defence against pathogen invasion and infection.

Cytokines trigger immune cells to collect at the site of infection (cuts, for example). Specialised white blood cells called Phagocytes remove foreign substances from the blood and lymphatic systems, such as dirt, dust, pathogens, etc. Phagocytes are not specific – they ingest any and all foreign materials.

Skin helps to flush away bacteria with sweat and desquamation (peeling of the skin). The gastrointestinal and respiratory tracts both have cilia to help to remove foreign bodies. Mucous also helps to trap these foreign bodies, preventing them from entering any further into the body and causing damage – tears and saliva do this.

One of the first responses to infection is inflammation. Blood cells dilate and collect at the site, causing the red, swollen appearance. Histamine is also produced.

Acquired immunity involves specific cells, which recognise certain antigens and bind to them – vaccines are also acquired immunity.
This type of immunity is only formed after exposure to a pathogen. ‘Memory’ white blood cells work with lymphocytes to create antibodies, which last for very long periods of time and provide immunity. Vaccines are dead or weakened strains of a virus, which are injected into the body to provoke a reaction. The white blood cells are able to easily fight off the virus, usually with no symptoms showing, and memory cells remember these antigens.


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