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

Supports the immune system's functioning. —Sarah Bence, Verywell Health, 30 Nov. 2025

Type 1 occurs when the body’s immune system destroys the cells in the pancreas that produce insulin, while type 2 develops when the body still makes insulin but no longer responds to it effectively. —Kelly McGreal, FOXNews.com, 29 Nov. 2025

Invasive listeriosis is a potentially life-threatening event, especially for newborns, adults over the age of 65, and those with weakened immune systems. —Matthew Robinson, MSNBC Newsweek, 28 Nov. 2025

Other scientists have used AlphaFold to discover the structure of Vitellogenin, a protein that plays a key role in the immune system of honeybees. —Jeremy Kahn, Fortune, 28 Nov. 2025

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