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 healthy people can recover in four to seven days without treatment, some vulnerable groups, like children under 5, adults 65 and older, and those with weakened immune systems, may experience more severe illness that requires medical treatment or hospitalization. —Fernando Cervantes Jr, USA Today, 29 May 2026

The immune system gets elevated. —Cindy Hsu, CBS News, 28 May 2026

In two international studies, about 1 in 5 patients given the experimental drug saw their virus reduced to levels low enough for the immune system to keep in check. —CNN Money, 28 May 2026

Mast cell stabilizers block the breakdown of mast cells – part of the body’s immune system – which helps reduce the release inflammatory chemicals. —Neelam Patadia, The Conversation, 27 May 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