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The Immune Response

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Updated September 25, 2006

When a foreign substance such as a bacteria or a parasite enters the body, the immune system activates to protect against the invader. But how does the immune system work?.

Illustrations of Immune System Structures

First the body must recognize the invader. Specialized cells attach to the invader and "present" it to the T-cells. This signals the T-cells to migrate and multiply in an effort to destroy the invader. The T-cells activate to help rid the body of the invader. HIV attacks T-cells, breaking down the body's first line of defense, therefore rendering the body defenseless against infection. There are two key pieces to this process, the antigen and the antibody.

Details of the Immune Response

What are Antigens?

Antigens reside on the surfaces of cells. They are identifiers that tell the body a cell belongs in the body or is foreign and must be eliminated. Each cell in our body has an antigen that tells the immune system that it is part of us and should not be eliminated. Bacteria cells have different antigens that tell the body they are foreign and must be destroyed. It is through antigens that the immune system knows which cells to attack and which to leave alone.

What are Antibodies?

Antibodies are the body's complement to antigens. Each antigen is specific to each cell. Furthermore, each antigen has a specific complementary antibody. Think of the antigen as a lock and the antibody as its key. When the key is in the lock, the antigen's cell is unable to reproduce. In other words, when the antibody attaches to its complementary antigen, the cell the antigen is attached to can't reproduce. It is through this arrangement that invading foreign cells are destroyed by the body. When the body detects foreign antigens, it produces antibodies that will join with the antigen, rendering it unable to reproduce. Without the ability to reproduce, the infectious invader dies off and the body stays healthy. This system is effective in most cases. Unfortunately, in the case of HIV the body's antibodies are not strong enough to fight off the infection, leaving the HIV free to multiply and damage the immune system.

HIV Does the Damage

The immune system is the body's miraculous way to protect itself. Unfortunately HIV damages that system. In order to stay healthy and maintain an effective immune system, people infected with HIV must be regularly monitored by a doctor specializing in HIV, must choose a healthy lifestyle, and must take their prescribed therapies consistently and correctly. Protect the immune system and you will live a long healthy life.
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