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The Immune System

The immune system is a body-wide network of organs, tissues, cells, and proteins that fights against foreign invaders. These invaders—germs or pathogens—are infection-causing organisms such as bacteria, viruses, parasites, and fungi. When there are enough foreign invaders, they can make us sick. The components of the immune system work together to fight these attacks and keep the body strong and healthy.

Major Organs

The major organs and tissues of the immune system are the thymus, liver, bone marrow, tonsils, lymph nodes, spleen, and blood.

Move the mouse over the immune system organs to learn more about them.