People With No Immune Systems

You live in a world of germs and you're at war. Your body's constant, warm environment, rich in nutrients, is an ideal home, where tiny organisms can thrive. Their aim is to get in. Your body's job is to keep them out. Through advances in cancer research, scientists now believe more than 100 million immune cells exist. For every virus or bacterium, there seems to be an immune cell specifically designed to hunt down and destroy …

…by antibodies they received from their mothers before birth. Babies who are nursed can also receive some antibodies from breast milk; these help to protect the digestive tract. However, babies with no immune system at birth must spend a great deal of their life, if not their entire life, building up enough of an immune system to leave a protected environment and return to the outside world where infections can be spread through the wind.