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 class learned that ajo (garlic) keeps your heart and immune system strong and that espinaca (spinach) helps your muscles grow like a superhero. —Fort Worth Star-Telegram, 3 Feb. 2026

This includes people with weakened immune systems, children younger than 5 years old and adults 65 or older. —Maia Pandey, jsonline.com, 3 Feb. 2026

Gut microbes help train the immune system to recognize and respond quickly to real threats, such as pathogens or cancerous cells, Koh said. —Miriam Fauzia, Dallas Morning News, 3 Feb. 2026

Even a mild case of measles can lead to lingering damage to the immune system known as immune amnesia, making a person more vulnerable to other diseases ranging from flu to tuberculosis. —Tom Gavin, EverydayHealth.com, 3 Feb. 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