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

For four weeks, he was monitored at Holtz to make sure everything went well and to keep him safe as his immune system recovered. —Michelle Marchante, Miami Herald, 19 June 2025

In addition, serious and sometimes fatal infections in older adults and people with weakened immune systems. —Marni Rose McFall, MSNBC Newsweek, 19 June 2025

It is considered a serious condition and can be dangerous or life-threatening, especially to older adults, people with weak immune systems, and pregnant women. —Natalie Neysa Alund, USA Today, 19 June 2025

Exposure to wildfire smoke can cause inflammation and weaken the immune system, particularly when its particles penetrate the lungs and the bloodstream. —Evan Bush, NBC news, 12 June 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