The immune system is a vast network of cells, tissues, and organs that coordinate your body’s defenses against any threats to your health. Without it, you’d be exposed to billions of bacteria, viruses, and toxins that could make something as minor as a paper cut or a seasonal cold fatal. So how does it work?

Phagocytes! Lymphocytes! Yay, Leukocytes! Find out in this TED Ed lesson by Emma Bryce with animation by Cabong Studios.

Follow this lesson with three related smart videos: Flu Attack! How A Virus Invades Your Body, Cell vs. virus: A battle for health, and Immunity and Vaccines Explained.

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