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

While most people recover fairly quickly from HMPV, people with weakened immune system or other medical conditions, or who are very young or old, are more likely to suffer serious illness, the Mayo Clinic said. —Don Sweeney, Sacbee.com, 3 Mar. 2026

Nutrition or Diet A balanced diet generally supports the immune system to fight cancer cells. —Doru Paul, Verywell Health, 27 Feb. 2026

That confirms, with data from individual cells, that differences in the host’s immune system, not the virus’ behavior, are behind these effects. —Veronique Greenwood, Time, 27 Feb. 2026

Scientists at the University of Chicago Comprehensive Cancer Center developed a CAR-T platform that can remove and replace the antigen-recognizing portion of CAR-T in vivo, which could better protect a patient’s immune system. —Amanda Erickson, STAT, 27 Feb. 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