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

New drugs to treat alopecia areata called JAK inhibitors were approved in just the last few years, which target the part of the immune system that has become overactive and attacks the hair follicles. —Sydney Lupkin, NPR, 23 Nov. 2025

Astronauts’ immune systems may benefit from a dirtier International Space Station. —Victor J. Blue, Harpers Magazine, 23 Nov. 2025

This vitamin, also known as retinol, supports healthy vision and eyes as well as your immune system and reproductive health, among other bodily functions. —Kelly Burch Published, Verywell Health, 22 Nov. 2025

Scientists have found the clearest evidence yet that Epstein-Barr virus (EBV) – which nearly all of us carry for life – is directly responsible for hijacking our immune system's cells to cause lupus, a chronic disease that affects up to a million Americans. —New Atlas, 21 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