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

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

Together, these discoveries suggest that nutrients from both plant and animal sources may work in complementary ways to support the immune system.

From Science Daily • Apr. 10, 2026

Alongside steroids and emollients, there are immunosuppressants; newer drugs which modify the immune system; and phototherapy which uses UV light.

From BBC • Apr. 10, 2026

“Your immune system hasn’t been exposed to a lifetime of common viruses and bacterial infections. It hasn’t had time to get experience with fighting these infections. It hasn’t had time to get strong.”

From "Everything, Everything" by Nicola Yoon