Final answer:
Autoimmune diseases involve the misdirected attack of the immune system against the body's own cells through the production of autoantibodies, which can lead to a variety of symptoms and complex types of hypersensitivity reactions.
Step-by-step explanation:
An autoimmune disease occurs when the immune system incorrectly identifies normal, healthy cells as foreign invaders and begins to attack them. This immune system dysfunction involves the production of antibodies known as autoantibodies, which are directed against the body's own cells, tissues, or organs. For example, in myasthenia gravis, an autoimmune disease, antibodies target muscle-cell receptors, causing muscle weakness. In systemic lupus erythematosus, the immune system mounts a diffuse autoantibody response against the individual's own DNA and proteins, leading to various systemic symptoms. It is crucial to note that autoimmune diseases can involve various types of hypersensitivity reactions, including types II, III, and IV, which underline the complexity of these diseases.