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

Young children, travelers, gay or bisexual men, and those with weakened immune systems are at a higher risk of contracting Shigella, the CDC cautioned. —Melissa Rudy, FOXNews.com, 14 Apr. 2026

Known as Piwi-interacting RNAs, piRNAs help regulate development, regeneration and the immune system. —Scott Lafee, San Diego Union-Tribune, 14 Apr. 2026

These microscopic, bubblelike structures carry proteins, toxins and other molecular signals that influence how the immune system of the host responds. —Panteha Torabian, The Conversation, 14 Apr. 2026

Johansson's immune system has not fully recovered. —Mary Eber, CBS News, 13 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