In this program students learn that infectious diseases are caused by microscopic foreign invaders called pathogens, while noninfectious diseases can be due to a variety of factors that include heredity, environment or lifestyle choices. Viewers get a close-up look at the immune system's three lines of defense; protective barriers like skin and mucus, the inflammatory response and the lymphatic system. Included is an interview with a doctor who explains the special role white blood cells play.

Teacher's guide and student worksheet available under Additional info tag.