Immune Response

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Innate immunity and inflammation

One's innate immunity are the barriers that keep harmful materials from entering your body and form the first line of defense in the immune response. Some of these barriers are: the skin, stomach acid, mucous (traps microorganisms and small particles), the cough reflex, and enzymes in tears and skin oils. If an antigen gets past the external barriers, it is attacked and destroyed by other parts of the immune system. Innate immunity also includes those things that make humans resistant to many of the diseases of animals.

The immune system includes certain types of white blood cells. It also includes chemicals and proteins in the blood (such as complement proteins and interferon). Some of these directly attack foreign substances in the body, and others work together to help the immune system cells.

The inflammatory response (inflammation) is part of innate immunity. It occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. Chemicals including histamine, bradykinin, serotonin, and others are released by damaged tissue. These chemicals cause blood vessels to leak fluid into the tissues, resulting in localized swelling. This helps isolate the foreign substance from further contact with body tissues.

The chemicals also attract white blood cells that "eat" microorganisms and dead or damaged cells. The process where these white blood cells surround, engulf, and destroy foreign substances is called phagocytosis, and the cells are collectively referred to as phagocytes. Phagocytes eventually die. Pus is formed from a collection of dead tissue, dead bacteria, and live and dead phagocytes.

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