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

Most infections go away on their own as the immune system clears them, but some persist and can cause cellular changes that can become cancerous over time. —Katia Hetter, CNN Money, 24 Apr. 2026

Children, older adults, pregnant people and those with weakened immune systems are all more vulnerable to complications. —Hanna Wickes, Miami Herald, 24 Apr. 2026

The immune systems of eight of the 16 in the trial responded to the vaccine. —The Editorial Board, Chicago Tribune, 24 Apr. 2026

Managing stress levels helps regulate the immune system. —Cristina Mutchler, Verywell Health, 24 Apr. 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