Oh no! It looks like a virus has entered the body! The white blood cells have come out of the bone marrow and into the blood stream to fight it, but they may need some help getting around...
The white blood cells did not act fast enough. The body starts getting sick and tired. The lymph nodes start swelling and producing fluid to help fight the sickness.
With help from the lypmph nodes, the white blood cells can fight the virus. There are now more white blood cells in the body. The heart also helped by circulating the blood containing white blood cells through the body. The brain made the body tired, so the body got some rest, wich also helped.