There once was a castle. All around that castle was bad blue people that wanted to get inside the castle, pathogens. Lucky for the castle it had physical barriers to defend itself. It had its gate and its mote to keep the blue people out.
Unfortunately for the castle sometimes its physical barriers don't work. The castles gate had fell. Now the castle has to rely on its defense on the inside.
One of those defenses is John. John is a phagocyte that patrols the castle and deals with a problem when he finds a problem. John has found some evil blue people intruder pathogens, so he is going to fight them off.
After some time John the phagocyte gets worn out and can't fight off any more pathogens. Once the problem gets too bad the lymphocytes come in. Joe the B cell lymphocyte tries to develop an antibody to stop the blue people pathogen from spreading.
Joe the B cell developed a cage as the antibody for the pathogen so that it won't keep spreading around the castle. While Joe is doing that Jeff the killer T cell kills the infected areas. His smaller brother Jim the helper T cell helps rejuvenate the B celsl so they can make more anti-bodies.
Once all the blue people pathogens are gone the suppressor T cells come in and tell the other T cells and B cells that the threat is gone. Now the castle has active immunity and is ready for the next time the blue people pathogen come back.