Did you know that God put a police force right inside your body? It fights disease. Under your skin, white blood cells find viruses and bacteria. “Intruder! Intruder!” they scream. Then, wham! The cells start chowing down on the enemy.

White blood cells are part of your immune system. Think of them as a crime squad that has spent years memorizing mug shots. The cells remember germs that have invaded your body before. Their job is to catch the prowlers—before you get sick. But can these slick cells stop a horrible disease like cancer?

In many cases, they can’t. That’s because cancer wears a great disguise. It doesn’t look like an intruder. That’s because it isn’t, exactly. Cancer cells are your own body’s cells. But they don’t follow your body’s rules. That causes all kinds of sickness in the body. To find and fight cancer, the immune system needs help.

And help is on the way. Researchers in Chicago studied cancer cells. They gave cancer patients certain drugs. Some of the drugs marked cancer cells. Suddenly, the patients’ bodies could recognize the cancer cells as intruders. It was like cancer’s disguise had been torn off!

Scientists call the new treatment immunotherapy. Before immunotherapy, doctors got rid of cancer in other ways. They cut it out with surgery. They used radiation or chemicals to kill it. Doctors will still use these methods. But immunotherapy will make some kinds of cancer much easier to get rid of.

Like other cancer treatments, immunotherapy isn’t perfect. The drugs that mark cancer cells can also make patients very sick. Patients must think carefully before they use it. But for many people fighting cancer, the body’s police force is doing a great job!