immune system

American  

noun

Anatomy.

1. a diffuse, complex network of interacting cells, cell products, and cell-forming tissues that protects the body from pathogens and other foreign substances, destroys infected and malignant cells, and removes cellular debris: the system includes the thymus, spleen, lymph nodes and lymph tissue, stem cells, white blood cells, antibodies, and lymphokines.

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immune system Scientific  

1. The body system in humans and other animals that protects the organism by distinguishing foreign tissue and neutralizing potentially pathogenic organisms or substances. The immune system includes organs such as the skin and mucous membranes, which provide an external barrier to infection, cells involved in the immune response, such as lymphocytes, and cell products such as lymphokines.

2. See also autoimmune disease immune response

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immune system Cultural  

1. The system in the body that works to ward off infection and disease. Central to this system are the white blood cells. Some white blood cells produce antibodies in response to specific antigens that may invade the body; others function as scavengers to fight infection by destroying bacteria and removing dead cells.

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Etymology

Origin of immune system

First recorded in 1960–65

Example Sentences

Thanks to UK researchers it was quickly identified that the drug was effective at reducing an immune system over-reaction in Covid patients that led to fatal lung damage.

From BBC • Apr. 16, 2026

A new study suggests a path toward next-generation cancer treatments by training the immune system to respond more efficiently and aggressively.

From Science Daily • Apr. 14, 2026

A modified herpes virus is injected into tumors, which causes cancer cells to burst and release flares that activate and train the immune system to attack cancer cells throughout the body.

From The Wall Street Journal • Apr. 14, 2026

The patient's immune system had been "completely replaced" by the donor's, sqaid study co-author Marius Troseid of the University of Oslo.

From Barron's • Apr. 13, 2026

Another common response of ours is to mobilize our immune system.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond