Final answer:
Autoimmunity is an exception to the rule that a substance must be foreign to create an immune response. Autoimmune diseases occur when the immune system attacks the body's own cells due to a breakdown in immune tolerance. Treatment for autoimmune diseases involves immunosuppressive drugs and corticosteroids.
Step-by-step explanation:
An exception to the rule that a substance must be foreign to create an immune response is autoimmunity, which can result in autoimmune diseases.
Autoimmune diseases occur when the immune system attacks the body's own cells. This happens due to a breakdown in the immune system's ability to distinguish self from non-self. In normal states, the immune system induces tolerance and does not mount an immune response against the body's own cells. However, with autoimmunity, there is a loss of immune tolerance, leading to the development of autoimmune diseases.
Autoimmune diseases can have various symptoms that come and go, making diagnosis challenging. The mechanisms responsible for autoimmune diseases involve type II, III, and IV hypersensitivity reactions. Treatment often includes immunosuppressive drugs and corticosteroids to control the inappropriate immune response.