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Immune System
General Purpose: To inform
Specific Purpose: To explain to my listener how immune system is important to body.
Central Idea: Immune system is excellent network in our body. It help to protect our
body from germs and diseases caused by them.

INTRODUCTION
I. In the late1880s, Russian scientist Elie Metchnikoff was examining wandering cell in sponges and starfish. He looked through his microscope and watched them move. They would stick out one part of their cell body and pull the rest after it. He thought about what he was seeing. He thought may be this is what happens with the cells in blood. Perhaps this was how the body fought off disease.

II. Although he had not seen the cells eat germs, but he believed in his theories. His theories later proved true, scientist discovered more about blood cells and their effect on disease germs. They discovered other germ-fighting blood cells. Now doctors refer to all of these body defenses as the immune system. They use their knowledge to prevent and cure disease. Today, I’d like to give you some information about our immune system which helps us to protect our body from invaders.

(Transition: Let’s start with different defensive system.)

I. Defensive systems
A. The first line of defense against bacteria, viruses, and other microbes is the skin and the lining of the respiratory, digestive and urinary systems and a break in these linings, however, permits microorganisms to enter in body.
1. The skin, for instance, produces a slightly acidic secretion that impairs bacterial growth.
2. The stomach lining releases hydrochloric acid that destroys ingested bacteria.
3. Saliva contains an enzyme that dissolves the cell wall of bacteria, killing them.

B. The first line of defense is not perfect so tiny breaks can occur, allowing viruses and...