Itolerance, and the more intensive reaction resulting in Celiac
disease, is essentially due to the body's development of an immune
response to certain molecules in wheat.
In most people the immune system does not recognized these molecules and they are ignored, like the immune system usually ignores the innate molecules of the human body. The disease develops by the immune system learning to recognize the molecules in wheat and thus reacting to them. This also happens at times to innate molecules of the human body, resulting in autoimmune diseases.
How does the immune system learn to recognize molecules it should ignore?
One way, is that the immune system recognizes a foreign molecule, and that foreign molecule is similar to the ignored molecule. The immune system increases cell production of cells that recognize the foreign molecule. So many cells are produced that there is some variation in what some descendant cells recognize. When one of those variations is to a molecule that should be ignored, disease develops.
Some people can recognized a particular pattern of development. At first they notice a reaction only to some isolated source(s), one particular food. Then later, the reaction becomes generalized to a whole class of foods, such as any containing wheat.
If you have recognized the pattern and can identify any sources, please write. Gluten at glutenintolerance dot biz.