immune system

noun

: the bodily system that protects the body from foreign substances, cells, and tissues by producing the immune response and that includes especially the thymus, spleen, lymph nodes, special deposits of lymphoid tissue (as in the gastrointestinal tract and bone marrow), macrophages, lymphocytes including the B cells and T cells, and antibodies

Examples of immune system in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
While bacteria and viruses set off immediate alarm in our immune system, allergies follow a different path. — Michael Eisenstein, Washington Post, 19 Oct. 2026 What’s Happening Researchers are continuing to redesign peptides, the short chains of amino acids the body uses to signal, build muscle and regulate the immune system, so they can be swallowed rather than injected. — Samantha Agate, Kansas City Star, 16 Oct. 2026 For now, the study identifies a previously underappreciated part of the immune system that could help overcome one of SCLC’s most persistent defenses. — New Atlas, 15 Oct. 2026 But by closely analyzing the immune systems of patients in their trials, Moderna and Merck could in theory build even better software. — Jason Mast, STAT, 15 Oct. 2026 See All Example Sentences for immune system

Word History

First Known Use

1899, in the meaning defined above

Time Traveler
The first known use of immune system was in 1899

Rhymes for immune system

See All Rhymes for immune system

Browse Nearby Words

immune surveillance
immune system
immunist
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Cite this Entry

“Immune system.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/immune%20system. Accessed 22 Oct. 2026.

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Kids Definition

immune system

noun
: the bodily system that protects the body from foreign substances, cells, and tissues by producing the immune response and that includes especially the thymus, spleen, lymph nodes, lymphocytes, and antibodies

Medical Definition

immune system

noun
: the bodily system that protects the body from foreign substances, cells, and tissues by producing the immune response and that includes especially the thymus, spleen, lymph nodes, special deposits of lymphoid tissue (as in the gastrointestinal tract and bone marrow), lymphocytes including the B cells and T cells, and antibodies

More from Merriam-Webster on immune system

Britannica.com: Encyclopedia article about immune system

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