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Immune System

The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by “foreign” invaders. These are primarily microbes—tiny organisms such as bacteria, parasites, and fungi that can cause infections. Viruses also cause infections, but are too primitive to be classified as living organisms. The human body provides an ideal environment for many microbes. It is the immune system’s job to keep them out or, failing that, to seek out and destroy them.

Understanding the Immune System

  • What is the Immune System?
  • Self and Nonself
  • The Structure of the Immune System
  • Immune Cells and Their Products
  • Mounting an Immune Response
  • Immunity: Natural and Acquired
  • Disorders of the Immune System
  • Immunology and Transplants
  • The Immune System and the Nervous System
  • Research Frontiers in Immunology
  • Glossary
  • Research

    Although scientists have learned much about the immune system, they continue to study how the body launches attacks that destroy invading microbes, infected cells, and tumors while ignoring healthy tissues. New technologies for identifying individual immune cells are now allowing scientists to determine quickly which targets are triggering an immune response. Improvements in microscopy are permitting the first-ever observations of living B cells, T cells, and other cells as they interact within lymph nodes and other body tissues.

    In addition, scientists are rapidly unraveling the genetic blueprints that direct the human immune response, as well as those that dictate the biology of bacteria, viruses, and parasites. The combination of new technology and expanded genetic information will no doubt reveal even more about how the body protects itself from disease.


    News and Media

    Persistent Bacterial Infection Exploits Killing Machinery of Immune Cells—Nov. 2, 2008

    NIH Scientists Discover Crucial Control in Long-Lasting Immunity—Oct. 10, 2008

    NIAID Media Availability: People with Job’s Syndrome Lack Specific Immune Cells—Mar. 14, 2008

    All Autoimmune Diseases News and Media


    The print version is available: Understanding the Immune System: How It Works (PDF). All artwork is by Jeanne Kelly and may not be repurposed.


    Volunteer for Clinical Studies
    Help people who are suffering from chronic, serious, or life-threatening illnesses related to the immune system by volunteering  for NIAID clinical studies on ClinicalTrials.gov.

    Glossary

    Look up definitions to help you understand the immune system.

    See Also

  • Autoimmune Lymphoproliferative Syndrome (ALPS)
  • Selected NIAID Science Advances, 2007-2008 (PDF)
  • Immunology: Curious About B-Cell Activation
  • Primitive Marine Creature Holds Clues to Immune System History
  • Related Links

    The Immune System from the National Cancer Institute

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    Volunteer for Clinical Studies
    Help people who are suffering from chronic, serious, or life-threatening illnesses related to the immune system by volunteering  for NIAID clinical studies on ClinicalTrials.gov.

    Glossary

    Look up definitions to help you understand the immune system.

    See Also

  • Autoimmune Lymphoproliferative Syndrome (ALPS)
  • Selected NIAID Science Advances, 2007-2008 (PDF)
  • Immunology: Curious About B-Cell Activation
  • Primitive Marine Creature Holds Clues to Immune System History
  • Related Links

    The Immune System from the National Cancer Institute