It sound so simple, but it is a complicated subject. As the name implies, the immune system orginates in a variety of places in the body all providing various agents doing various things.
The point of this article is not to bury us all under the minutae of immunology and medical jargon, so lets not do that thing. Immunology is cell warfare and everyone loves a good scrap, so lets attack this thing sideways.
First and foremost – Who is the enemy?
The immune system protects the body against attacks from an array of nasties (pathogens) that infect the human body and do damage: bacterial, viral. fungal, prion (responsible for mad cow disease), algal (as in blue green algae) and parasites (worms etc)