What is an Autoimmune Disease?
Your body is constantly under attack from other organisms, in the form or viruses, bacteria, and other foreign invaders. Without protection, your chances of surviving these attacks are quite slim. As a consequence, a complex system of defenses has been created to respond to these attacks The immune system protects the body from foreign invaders. In order to do this, it must be able to recognize the parts of the body that are not foreign. In persons with autoimmunity, the mechanism by which the immune system distinguishes foreign bodies from your own tissues and organs breaks down, and the immune system attacks a part of yourself. There are many autoimmune disorders that occur in many places inside the human body. 
What is Coeliac Disease?
Coeliac disease occurs when the immune system attacks the tissue and lining of the small intestine. It can begin when you are a child, and may continue your entire life. In most cases, there are symptoms, which include:
- Pain and discomfort
- Chronic constipation and diarrhea
A person may not have any symptoms of Coeliac Disease. (The medical term for having no symptoms is called asymptomatic.) In children, a failure to thrive can also be a symptom, because the small intestine is where nutrients are absorbed by the body. Vitamin deficiencies are a consequence. 
What causes Coeliac Disease?
Common grains, like wheat, barley, and rye, contain a protein called gluten, and this protein causes a reaction in the small intestine. The resulting inflammation affects the villi lining of the small intestine, which is the lining that absorbs nutrients. The more gluten a person ingests, the more the lining becomes inflamed, and this causes the lining to wither, or atrophy. It becomes a vicious cycle, and the small intestine becomes less able to absorb nutrients the more it atrophies.
Is there a cure for this disease?
Presently, a gluten-free diet is the only way to avoid the inflammatory reaction. Avoiding gluten is not easy, as grains can be found as fillers in a lot of processed foods. However, nutritionists are beginning to recognize gluten as a source of concern, and public awareness is growing. 
More information on Coeliac Disease can be found online. Try the Celiac Disease Foundation or Celiac.com.
Photograph by Pdeitiker. Original uploader was Pdeitiker at en.wikipedia