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

The vaccine does not cause an infection or Ebola symptoms, but trains the immune system to give protection.

From BBC • May 22, 2026

Professor Jesus Gil, senior author of the study and Head of the Senescence group at the LMS, said the next step is understanding how the treatment affects the immune system.

From Science Daily • May 13, 2026

He said his message to the cruise-ship passengers now in quarantine is to stay positive since stress can weaken an immune system.

From The Wall Street Journal • May 12, 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

However, if the bacilli become active—when someone’s immune system is compromised, as with AIDS—they multiply rapidly into a bone-eating, lung-consuming illness that, unless treated, is fatal.

From "Mountains Beyond Mountains" by Tracy Kidder and Michael French