Quite simply, their job is to kill anything they don't recognise as being part of you! Or to put it another way, they attack and kill germs and bacteria that they find in the blood when you have an infection and once they have done that you recover.
They don't go hunting for these foreign bodies in your blood, they just bump into them by accident and if they don't like them, they attack. This is a bit random, which is why it can take time for them to help you recover from an infection. Unfortunately they can't kill everything they meet, which is why we need medicine as well.
Red blood cells, on the other hand, absorbe oxygen from your lungs and transport it around the body, to your brain and muscles and other organs.Then they release the oxygen to the cells in these areas.
They don't go hunting for these foreign bodies in your blood, they just bump into them by accident and if they don't like them, they attack. This is a bit random, which is why it can take time for them to help you recover from an infection. Unfortunately they can't kill everything they meet, which is why we need medicine as well.
Red blood cells, on the other hand, absorbe oxygen from your lungs and transport it around the body, to your brain and muscles and other organs.Then they release the oxygen to the cells in these areas.