Like Mrs. D stated, there are parasites which can cause the PN and/or autoimmune diseases. You can get checked to see if you have offending parasites. They can do stool samples to check. Sometime you need to do two test a few week apart because of their life cycles. Some parasites cause what's called leaky gut which sets you up for autoimmune and allergies because it compromises the lining of the gut. On the flip side, like the article implies, by introducing a parasite, it calms an overactive immune system by giving the immune system a real target. I guess it would be a natural immmuno-suppresant.

I think I would first take the approach of changing your diet and add in some form of probiotic first to see if that helps.