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

Harmful molecules called free radicals show up, certain enzymes start breaking down collagen and the immune system is activated. — Leslie Baumann, Miami Herald, 9 July 2026

This loss is often the result of an autoimmune process in which the body's immune system mistakenly attacks those cells. — Daryl Austin, USA Today, 8 July 2026

Doctors are also more likely to order the test for those at higher risk of complications from their infection, including very young babies and children, and people with weakened immune systems. — Alice Park, Time, 8 July 2026

An air of credibility Peptides are a string of amino acids — smaller than a protein — that often act as signaling molecules in our bodies and help regulate the immune system, metabolism and many other critical functions. — Will Stone, NPR, 8 July 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