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 recover, some — particularly young babies, pregnant people and those with weak immune systems — are at higher risk of developing dangerous complications such as pneumonia, brain swelling, blindness or even death. —Devi Shastri, Los Angeles Times, 20 June 2026

While most recover, some — including young babies, pregnant people and those with weak immune systems — are at higher risk of developing dangerous complications like pneumonia, brain swelling, blindness or even dying. —Devi Shastri, Fortune, 20 June 2026

This herb may boost the immune system’s response to certain infections, including upper respiratory infections and skin infections. —Carrie Madormo, Verywell Health, 20 June 2026

When the sugar enters the bloodstream through a lone star tick bite, the body's immune system can begin treating it as a threat. —CBS News, 19 June 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