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

One reason might be that the mother’s immune system is adjusting to protect the baby.

From The Wall Street Journal • May 14, 2026

Prebiotic fiber, from sources like legumes, fortifies the good bacteria in your digestive system and, in turn, benefits your metabolism and immune system.

From MarketWatch • May 10, 2026

The project is being led by Danielle Jex, a senior lecturer in immunology, and will investigate whether chemical signals released by endometriosis cells can help cancer cells survive and avoid the immune system.

From BBC • May 8, 2026

These experiences may also prompt the adaptive immune system, which helps the body recognize and respond to outside threats.

From Science Daily • May 4, 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