What is tolerance? How is it critical to the normal functioning of the immune system

The inhibition of an immune response in contradiction of a specific antigen is termed as tolerance. For example, the immune system is usually lenient of self-antigens, so it does not generally attack the tissues, cells, and organs of one's own body.

It plays a critical role in the immune system as if immunological self-tolerance is mislaid, the body develops autoimmunity against its own cells and tissues that turn out to be the source of the autoimmune disorder.