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

In laboratory and animal models, researchers at Dartmouth Health in New Hampshire found that the telmisartan causes more damage to cancer cells’ DNA, thus helping the immune system recognize and attack certain types of tumors. —Melissa Rudy, FOXNews.com, 31 Mar. 2026

For example, some promote growth hormones, while others modulate the immune system. —Will Stone, NPR, 31 Mar. 2026

The new vaccine takes a similar approach to Lymerix, delivering a surface protein found on Lyme bacteria so the body’s immune system generates antibodies against it. —Meg Tirrell, CNN Money, 31 Mar. 2026

Coccidioides can cause severe pulmonary disease and chronic infections in some cases, while Aspergillus species, especially drug-resistant strains, can lead to life-threatening infections in people with weakened immune systems. —Brandi D. Addison, USA Today, 30 Mar. 2026

Word History

First Known Use

1899, in the meaning defined above

Rhymes for immune system

• cryptosystem
• ecosystem
• intersystem
• multisystem
• photosystem
• subsystem

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