immune system

American  

noun

Anatomy.

immune systems plural

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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Other Word Forms

Noun Inflected Forms

• immune systems
  plural

Etymology

Origin of immune system

First recorded in 1960–65

Example Sentences

This allowed them to look for the "similarities and the differences in the important parts of the virus that the immune system responds to", recognising not just one variant but all of them.

From Barron's • Jun. 25, 2026

Others develop autoimmune gastritis, in which the immune system damages stomach cells involved in producing acid and intrinsic factor, the protein needed for vitamin B12 absorption.

From Science Daily • Jun. 25, 2026

The immune system responds, and the next time you eat red meat and related products it identifies those as a threat, resulting in an allergic reaction.

From The Wall Street Journal • Jun. 25, 2026

The young man described a kind of withdrawal: “My immune system broke down. I lost a lot of lean body mass.”

From Salon • Jun. 22, 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