I am vaguely familiar with Dalfampridine and there is little research on it and herb interactions. There is a theoretical concern about combining it with Ginkgo extract but that seems like a bit of a stretch.. Beyond that there is nothing in the literature, but that is not because none have occurred, just no data one way or the other. As for herbs and MS, there are no herbs that are specifically CI for MS (and it depends on what you mean by immune stimulants), there are some anecdotal reports of Echinacea exacerbating MS, but that is about it.