The Immune System: Invaders and Defenders

We are surrounded by billions of bacteria and viruses which try to invade our bodies and reproduce. We call these invaders antigens and pathogens.  When we receive a cut and invaders enter the body, cells are destroyed. The dying cells trigger an automatic response called inflammation, which includes dilated blood vessels and increased blood flow. Inflammation is the body's equivalent to a burglar alarm. Once it goes off, it draws defensive cells to...