The immune system is the system of specialized cells and organs that protect an organism from outside biological influences.

(Though in a broad sense, almost every organ has a protective function - for example, the tight seal of the skin or the acidic environment of the stomach.) When the immune system is functioning properly, it protects the body against bacteria and viral infections, destroying cancer cells and foreign substances.

If the immune system weakens, its ability to defend the body also weakens, allowing pathogens, including viruses that cause common colds and flu, to grow and flourish in the body.

The immune system also performs surveillance of tumor cells, and immune suppression has been reported to increase the risk of certain types of cancer..

For more information about the topic Immune system, read the full article at Wikipedia.org, or see the following related articles:

Natural killer cell — Natural killer cells (also known as NK cells, K cells, and killer cells) are a type of lymphocyte (a white blood cell) and a component of innate ...  > read more

White blood cell — White blood cells (also called leukocytes or immune cells) are cells which form a component of the blood. They help to defend the body against ...  > read more

T cell — T cells are a subset of lymphocytes that play a large role in the immune response. The abbreviation "T" stands for thymus, the organ in which their ...  > read more

Antiviral drug — Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics, specific antivirals are used for ...  > read more

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