What is a key characteristic of autoimmune diseases?

A key characteristic of autoimmune diseases is that the body mistakenly attacks its own tissues. This occurs when the immune system, which is responsible for defending the body against foreign invaders like bacteria and viruses, becomes confused and targets healthy cells, organs, or tissues. This misdirected immune response can lead to inflammation and damage in various parts of the body.

Understanding this characteristic is crucial for recognizing how autoimmune diseases differ from other immune-related conditions. For instance, allergies (addressed in a different option) involve an immune reaction to external substances rather than the body attacking itself. Similarly, the emphasis of autoimmune diseases is not on external pathogens, but rather on the internal mistake of the immune system. The statement regarding increased immune response is also not specific to autoimmune diseases, as it can apply to various conditions, including infections and allergies. Hence, the distinctive feature of autoimmune diseases is the self-directed attack on the body's own cells.