I introduced readers to Zonulin a few entries back. To recap, Zonulin is a protein made by our bodies that creates loosening of tight junctions such as those in the gut, brain and testicles. The tight junctions control transportation of molecules across junctions.
An example is the prevention of food particles in the lumen of the gut from crossing over into the blood vessels. The food is broken down and nutrients extrapolated so as not to present foreign proteins to your own system. This is why we don’t make antigens to everything we eat.
However, some people do seem to produce antibodies to many foods and eventually, some of those with this issue produce antibodies to parts of themselves. This is what autoimmunity is. Some examples of autoimmune diseases are rheumatoid arthritis, thyroid disease, MS, psoriasis and even some forms of dementia. There are too many autoimmune disorders to list.