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 when testing the bespoke shots in animals, Grippin noticed that even the placebo shots — which contained mRNA entirely unrelated to the cancer — also activated the immune system to kill tumors. —Lisa Jarvis, Twin Cities, 8 Nov. 2025

While the greatest risk factor for Alzheimer’s is age, research increasingly finds that factors such as stress, hormonal changes that occur during menopause and immune system function play a role. —Jocelyn Solis-Moreira, Flow Space, 7 Nov. 2025

Some of the biggest perks of feeding pumpkin to your dog are the nutrients that support the immune system, promote a healthy coat and aid digestion. —Cody Godwin, USA Today, 7 Nov. 2025

But babies' immune systems can handle it, says Maldonado and other scientists. —NPR, 7 Nov. 2025

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