What's the immune system? Why is it so important?

The immune system is the body's defense against infectious organisms and other invaders ... One of the importantcells involved are white blood cells, also called leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.

The immune system is made up of cells, tissues, proteins, chemicals, and organs that work together. The immune system is a bodys defense against infectious organisms and other invadors