The Human Immune System
Why do you get sick? How do you get better? A disease is any _________________ that affects normal ___________________ of the body. Some diseases are _________________, or are inherited, others are caused by materials in the ______________________________, but most are caused by _____________________ such as bacteria, viruses, and fungi. Pathogens are “sickness-makers.” With pathogens all around us, the ___________________ system works like a protection system. Some of these defenses are simple _________________ keeping all invaders out, while others work like a security guard, trained to spot and ___________________ pathogens who have slipped past the barrier.