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

Patient 3’s immune system, however, didn’t produce as many antibodies after the procedure, suggesting that the therapy may not have efficiently reached its target, Whitton says. —Lisa Jarvis, Twin Cities, 19 Oct. 2025

Some research suggests cistanche may help with your immune system, memory, fatigue, and more. —Emmanuella Ogbonna, Health, 18 Oct. 2025

Relman said mirror bacteria could potentially evade critical parts of plant, animal and human immune systems, which would have difficulty detecting or killing them. —Katie Hunt, CNN Money, 17 Oct. 2025

The Multivitamin for Her is USP Verified, containing 23 key nutrients to provide support to the metabolism, bones, muscles, and immune system—from folic acid to calcium and iron. —Kiana Murden, Vogue, 17 Oct. 2025

Word History

First Known Use

circa 1919, 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