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

People who are unvaccinated, young children, pregnant women and people with weak immune systems are at the highest risk, officials said. —Jeff Capellini, CBS News, 28 Dec. 2025

Apple cider contains antioxidants that people claim can support your immune system, but the alcohol may have the opposite effect. —Kathleen Ferraro, Verywell Health, 28 Dec. 2025

May Manage Rheumatoid Arthritis Rheumatoid arthritis (RA) is an inflammatory autoimmune disease that causes the immune system to mistakenly attack healthy cells. —Cynthia Sass, Health, 23 Dec. 2025

Even mild soreness after a flu shot is a sign that your immune system is responding — an indication that your body is building protection. —Scott Lafee, San Diego Union-Tribune, 23 Dec. 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