Your immune system is housed in various areas of your body, like police precincts in a big city. Invaders (viruses, bacteria) can break through all of the typical entryways (mouth, nose, genitals, skin), but your security system only has a few locations—the thymus, bone marrow, spleen and lymphatic system and nodes.
When the white blood cells of your immune system spot a foreign invader, a type of white blood cell called a macrophage finds the germ, engulfs it, and digests it, sort of the way a security guard would stop and hold an intruder.
Your body has to determine whether the threat is real or not, and to do so, the macrophage calls for backup. Other immune system cells respond by traveling through the bloodstream to the invaded area. While they are en route, the white blood cell records and relays information about the invader. When the backup immune cells arrive on scene, they identify and obliterate the harmful invader, or let the benign one pass through security.
Now that you understand how the body works, learn these four ways to keep yourself from getting sick:

Practice Good Hygiene

Wash your hands or use antibacterial gel. Often. The most common way germs are spread is through contact with your hands that then touch your mouth or nose. Washing away the germs regularly helps minimize the damage (see below).

Get Plenty of Flavonoids

Flavonoids are great immune system strengtheners. Orange juice, tomato juice and citrus fruits are particularly good sources.

Don’t Use Antibiotics If You Have a Virus

Antibiotics can actually have a negative effect on your body if you have a virus. If your parents are pushing for a prescription from your doc, educate them about why antibiotics won’t work.

Get Your Flu Shot

Vaccinations keep you healthier. They keep away the bad bugs that can cause inflammation and diminish your athletic performance. Plus, not getting the flu is a way to help your team stay healthier, too.