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

Inflammation is the immune system’s response to fight against infection or disease. —Merve Ceylan, Health, 26 Oct. 2025

For the virus, these are havens protected from the immune system. —NPR, 24 Oct. 2025

The risk is highest for young children, frail or elderly people, and those with weakened immune systems. —Emily Kay Votruba, EverydayHealth.com, 24 Oct. 2025

Medical experts say that REDs can damage an athlete’s metabolism, their immune system, their cardiovascular health, their menstrual cycle, and their mental health, as well as their athletic performance. —George Ramsay, CNN Money, 23 Oct. 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