the ___________ system defends against _________ and destroys cancerous cells.
Please keep this in mind, and be sure to visit other parts of our site for more recent information! The immune system is the body's defense against disease. It defends the body from attack by foreign invaders such as bacteria, viruses, fungi and parasites, as well as cancerous cells. Normally, the immune system can distinguish between what belongs in your body (self) and what doesn't (non-self).