Hey John, how are you? That's a great question you posed. I asked the same thing too awhile back.
I wish I could find the website/articles that explained how LDN works, but I'm at the wrong computer! I think Bridget has them, and she does a great job of explaining it too.

I am by no means any sort of an expert, but I think LDN is more of an immunomodulator, from what I understand, and there are many clinical trials trying to figure out just exactly why and how it works so well for so many people with autoimmune disorders. So, you're right, no one knows for sure *exactly* how this stuff works, but the results of LDN use are so positively overwhelming, I really don't think the medical community has much of a choice but to figure out the mechanisms of just how it works so well. it's kind of neat that this is so patient-driven in a way - soooo many patients are now requesting this off-label and hugely benefitting, but no companies can really make a buck off it because it's already generic, so we can eliminate the possibility that this is just so-called big pharma getting greedy off it. People just take it because it seems to work, plain and simple.

I think the "immune system" should be renamed "immune systemS", because there are so many individual parts of this complex system, which function all at the same time. If an immune suppressing medication turns down one of the functions, the rest can keep ticking along like they usually do. Take enbrel for example - it can suppress some parts of the immune system, but not all. If it completely turned down all, then we'd be in really big trouble! The newer anti-TNF meds are getting increasingly more specific too, affecting just the minimal parts of the immune system necessary to be effective. It's going to be exciting to see what types of meds will come out in the next 20 years - the more specific, the more effective, and the less side effects they'll have.

Before I forget what I was originally trying to talk about here - One of the main effects of LDN is modulation of the immune system - by increasing endorphins (endorphins are immunomodulators), which increase and decrease different parts of the immune system, and thankfully, LDN seems to increase and decrease the right parts so that it actually benefits. Why exactly, is what alot of research is looking at right now. Also, LDN is very popular because effects are seen at very low doses, with nearly no side effects, and the stuff has been on the market at higher doses for a long time, which is reassuring in a way - we would have heard about it if there were some awful side effects.

Again, I'm no expert, and not a doctor, but this is just what I gather from some very late nights in the med library!