Duration: 05:09 | Inside you, a daily battle is being waged and your immune system is at the frontline. Most of the time, you may not even notice it's there, but over the course of your life your immune system will guard you against hundreds of potentially fatal threats. Emma Bryce explores the different components of this system and how, together, they do their vital work. [Directed by Felipe Grosso & Odirlei Seixas, narrated by Addison Anderson, music by Vadeco Schettini].