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Immune System

The immune system is the body's natural defense system that helps fight infections. The organs of the immune system include:

The tonsils, which are on either side of the throat at the back of the throat. The tonsils help make antibodies that fight infections.
Lymph nodes and lymphatics, which are found throughout the body. The lymphatics carry fluid, nutrients, and waste material between the body tissues and the bloodstream. The lymph nodes filter lymph fluid as it flows through them, trapping bacteria, viruses, and other foreign substances, which are then destroyed by special white blood cells called lymphocytes.
Thymus gland, which is found in the upper chest at the bottom of the neck, behind the breastbone. The thymus helps make antibodies that fight infection.
Bone marrow, which is found mainly inside the long bones, vertebrae, and pelvic bones of the body. The marrow makes white blood cells that destroy bacteria, viruses, and other organisms that cause infection.
Spleen, which is found in the upper left side of the abdomen. The spleen supports the immune system by helping it to recognize bacteria and other foreign substances and destroying them.

By	Healthwise Staff
Primary Medical Reviewer	Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer	W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last Revised	May 27, 2010

WebMD Medical Reference from Healthwise

Last Updated: May 27, 2010

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.