Definition of Anergy

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Anergy: A state of immune unresponsiveness. Induced when the T cell's antigen receptor is stimulated, effectively freezing T cell responses pending a "second signal" from the antigen-presenting cell. The delivery of the second signal by the antigen-presenting cell rescues the activated T cell from anergy, allowing it to produce the lymphokines necessary for the growth of additional T cells.

T cells are small white blood cells that orchestrate and directly participate in the immune defenses. Also known as T lymphocytes, they are processed in the thymus (which is why they are called T cells).