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

But opponents, including physician groups, warned that creating another exemption could lead to the spread of diseases that would harm children and affect other people, such as cancer patients, who have compromised immune systems. —Jim Saunders, Sun Sentinel, 27 Jan. 2026

Finally, pollution from ports along with potential spills can degrade the health of these animals and weaken their immune systems. —Rodrigo Tardin, The Conversation, 26 Jan. 2026

Zicam Travel can be stressful, and when my body is combating too much stress, my immune system is the first to remind me to slow down. —Kelsey Glennon, Travel + Leisure, 26 Jan. 2026

The risk is highest for the very young and very old, and those with weakened immune systems. —Tom Gavin, EverydayHealth.com, 26 Jan. 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