Well, I know for a fact that pig whipworm eggs (TSO) work for my allergies. Specifically, my annual hayfever got knocked out 100% by TSO without any antihistamine. Not 70%, not 90%, but 100%. This for a person who normally has red watery eyes, a scratchy throat and sneezes alot for about
two months each summer. Of course, allergies and IBD are very different things- my point being merely that TSO clearly does hook up to my immune system. TSO also dampened my UC, without a shred of doubt. (I know, some people say this of macaroon
cookies or spinach and sunflowers, but I can only relate my story). So I can speak from personal experience that parasites affect my immune system. And parasites are serious immune modulators in countless ways in animal models, as shown by scores of articles on pubmed.
Now, helminths may not be the key factor in IBD, only time will tell (I think it will be *one* key factor), and obviously microbiology is a key factor as Old Hat points out though I think it is a stretch to say it is THE key factor, since genes are also key, but the question then is why do normies not get IBD when exposed to the same "normal" bacteria that cause us to have IBD. Ultimately, these discussions can get like ping pong, but IBD is surely a combination of genes and environment, and those of us with IBD genes are the people who in many cases can suffer from less auto-immunity, when exposed to "normal" bacteria, when other otherwise fairly benign immune-modulators like parasites are con-currently present. The Eskimos, for their part, didn't have co-evolution of certain viruses, normal bacteria and parasites together and so are not "missing" the parasites needed to calm their aggressive microbial jumpiness, whereas my and your ancestors somewhere along the way were attuned to having both present together. Well, that is the gist of that pubmed paper (I have the full text also but can't legally attach it to this forum), based on a close genetic study of concurrent genes for auto-immunity and micro and macro-pathogen exposure, the pubmed link of which I posted earlier in this thread. Anyway, I think that worst case, helminths will prove to be IBD dampeners. Best case, for some people they could be a magic bullet, who knows.