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

The results suggested that the idea of using messenger RNA to train the immune system to attack cancer cells — an approach first devised decades ago — was ripe for further drug development. — Allison Deangelis, STAT, 5 Oct. 2026

This may be in part because the pandemic has spurred people on to find ways to strengthen their immune systems and improve their gut health. — Irenie Forshaw, TheWeek, 5 Oct. 2026

Last year, the prize went to three scientists researching the immune system. — ABC News, 5 Oct. 2026

Other potential causes are higher rates of chronic stress, depression and anxiety, as well as autoimmune diseases, which weaken the immune system, Curhan said. — Kaitlin Sullivan, NBC news, 2 Oct. 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