A lot of people think of the immune system as being controlled only by white blood cells but in my opinion that isn’t giving a lot of it enough credit!
All of your cells have the ability to recognise when they’re infected with a bacteria, virus or fungus. These cells can be anything from skin cells, to cells lining your lungs or guts. When these cells recognise that they have been infected with something they call white blood cells for help by producing help me signals (This is actually what cases swelling and redness when we get sick.) so that white blood cells can come and remove the infection.
White blood cells are like a special unit in our bodies. They are specially equipped to remove infections and can make molecules like antibodies which to stop bacteria growing and moving about. White blood cells can also kill off cells infected with viruses or tumours.