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

May Lower Inflammation Beta-carotene and other antioxidants in carrot juice can support the immune system. —Merve Ceylan, Health, 27 Sep. 2025

Some affect people’s immune systems, while others involve the uncontrollable multiplication of abnormal lymphocytes, according to Cleveland Clinic. —Hannah Dailey, Billboard, 26 Sep. 2025

Listeria monocytogenes, or Lm, is a bacterium that causes listeriosis, a serious infection that primarily affects older adults, individuals with weakened immune systems, pregnant women and their newborns. —Amaris Encinas, USA Today, 26 Sep. 2025

Usually, a person's immune system gets active when there's a threat in the body, but then settles once that threat is gone. —Stephanie Sengwe, PEOPLE, 26 Sep. 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