Outline the three steps your body’s immune system takes to fight off an infection

The first line of defense is the skin. It is the largest organ in the body and it acts as a barrier between invaders (pathogens) and the body. Microorganisms and bacteria cannot enter the skin unless it is broken. Inflammation is one of the signs that the first barrier has been destroyed.

The second line of defense is your cells. These are your white blood cells (leukocytes). There are different types but each one fights off the pathogens in order to protect you.

Once the bacteria has taken over what happens is that your white blood cells will increase and will activate your lymphatic system. This explains why you get high fever and the lymph nodules are swollen when one is sick. For instance, tonsils will inflame for those who have bacterial infection in the throat.  

They became more resistant.

There are  advantages  to being  multicellular  rather than unicellular. these include allowing: the  organism  to be larger.