To find out if a person has Coeliac disease, doctors look in the blood to see if they have the cells that attack the intestine when gluten is eaten. The protein that attacks the intestine is called an antibody. Antibodies are produced by white blood cells, and they normally stop illnesses from growing in the body, but in the case of coeliac disease, one of the antibodies thinks that gluten is something that will cause illness. Doctors can also look into the patient's intestines with a camera on a tube called an endoscope. This can show if the intestines are being or have been damaged, because of coeliac disease.