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

Children younger than age five, particularly infants, as well as adults age 50 and older with underlying medical conditions or those age 65 or older, are at higher risk of becoming seriously ill, as are people with weakened immune systems. — Adam Kovac, Scientific American, 6 Aug. 2026

Native to eastern Asia, Europe, and North America, the hen of the woods has long been used as a medicinal superfood known to boost the immune system and lower cholesterol, according to WebMD. — Katie Hill, Outdoor Life, 6 Aug. 2026

Before 1998, there was no medication to prevent HIV from destroying a patient's immune system, leaving them vulnerable to infections and rare cancers. — Durrie Bouscaren, NPR, 6 Aug. 2026

There are precautions that healthy adults in their 50s can take to protect themselves from the dangers of pneumococcal pneumonia, primarily making sure their immune system is effective and as strong as possible. — Mark Marino, PEOPLE, 6 Aug. 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