Not much. I think the evidence for gut barrier function having anything to do with human autoimmunity is close to zero. Unfortunately this sort of speculative idea that would once be had over a glass of beer is now being used to make money by review journals and they don't mind how little evidence there is.
As far as I know the gut barrier has nothing to do with self tolerance at all.
The zonulin research seems to be pretty well respected in regards to Celiac disease.