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

The body of evidence that mRNA vaccines can transform how researchers harness the immune system to treat cancer is growing. —Dannell D. Boatman, The Conversation, 17 Mar. 2026

And scientists are trying to tap the interconnection between circadian rhythms and the immune system through an approach called chronotherapy. —Lauren J. Young, Scientific American, 17 Mar. 2026

Young children, seniors, and those with weakened immune systems are most susceptible to illness. —Brandee Gruener, Southern Living, 16 Mar. 2026

Some parasites are harmless, even for people with weakened immune systems. —Sarah Boden, NPR, 16 Mar. 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