Let's look at autoimmune disease - what exactly does that mean?
Immune reactions are very important - your immune system protects you against infections & disease. To do so, the cells of the immune system recognize specific antigens - structures on the surface of everything: our own cells as well as pathogens like bacteria & viruses. When an immune cell finds something that isn't supposed to be there - be it a bug, a transplanted organ or a tumour - an immune reaction occurs. Your immune system then does everything in its power to attack the foreign intruders.
But what if your immune cells think your own cells are foreign? Then an autoimmune reaction occurs. Destruction of your own, normal tissues result. Disease is usually progressive, with relapses & remission.
I've mentioned autoimmune reactions on the Science Byte before - in type 1 diabetes mellitus, pancreatic cells are destroyed by the immune system. This is an example of organ-specific disease, where the inflammation is targeted to one area. Another example is multiple sclerosis, where the myelin sheath of neurons is destroyed. Systemic disease is when the reaction is against wide-spread self-antigens. For example, rheumatoid arthritis and systemic lupus are systemic diseases, with inflammation or lesions occurring throughout the body.
Have you had experience with an autoimmune disorder? I'd love to hear about it.