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

And effects seen in mouse immune systems may not directly apply to humans. —New Atlas, 4 Aug. 2025

The goal was to devise a treatment by 2030 that made patients’ muscles, brains, and immune systems twenty years younger; the winning team would get as much as eighty-one million dollars. —Tad Friend, New Yorker, 4 Aug. 2025

As with other autoimmune conditions, experts aren’t completely sure why the immune system gets triggered to overdrive and attacks hair follicles. —Ashley Abramson, Allure, 4 Aug. 2025

Unfortunately, Jamie ultimately suffers an extreme case of pneumonia that his weakened immune system cannot recover from and dies with Anna by his side. —Caroline Blair, People.com, 1 Aug. 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