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

Blood in the Urine C3G is a rare disease that occurs when the complement system (part of the immune system) becomes overactive. —Carrie Madormo, Health, 12 Jan. 2026

Garlic Some research suggests that garlic supports the immune system. —Cristina Mutchler, Verywell Health, 12 Jan. 2026

Chronic liver disease gets worse when the liver's immune system stays overactive, resulting in ongoing inflammation and scarring. —Pranjal Malewar, New Atlas, 11 Jan. 2026

Inebilizumab is a monoclonal antibody that targets CD19, an antigen found only on the surface of the immune system's B cells, in a process called B cell depletion. —Kerry Breen, CBS News, 10 Jan. 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