Immune system

The network of cells, tissues, organs, and molecules that detects and defends an organism against pathogens and other threats.

Innate immunity: The rapid, broadly targeted defenses present from birth that respond to shared features of threats. It provides the first response before tailored defenses develop.
Leukocyte: A white blood cell that participates in immune defense or regulation. Leukocytes are the mobile cellular workforce of immune responses.
Vaccination: The administration of a vaccine to induce protective immune responses against a disease. It trains adaptive defenses to respond more effectively to later infection.
Autoimmunity: An immune response directed against the body's own molecules or tissues. It illustrates what happens when tolerance fails and self becomes a target.
Immunological memory: The capacity of the immune system to respond differently after prior exposure to an antigen. Its duration and quality help determine lasting protection after infection or vaccination.
Adaptive immunity: Antigen-specific defense mediated by B and T lymphocytes, with the capacity for immunological memory. It builds targeted responses and memory after recognizing particular antigens.
Lymphocyte: A white blood cell, including B cells, T cells, and natural killer cells, involved in immune functions. These cells supply antigen-specific responses and other forms of defense.
Immunotherapy: Treatment that uses or alters immune mechanisms to address disease. It harnesses or redirects immune activity, particularly against cancer.
Immunodeficiency: A condition in which one or more components of immune defense are absent or impaired. It shows the consequences of defenses that cannot respond adequately.
Trained immunity: Longer-lasting changes in innate immune responses after prior stimulation, without antigen-specific memory. It raises questions about how broadly innate defenses can retain effects of past exposures.

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