Actually, it could be the exact opposite case. According to some things that I have read, chemo might actually be good for people with MS.

"Doctors report promising results using huge doses of a potent chemotherapy drug to treat autoimmune diseases including multiple sclerosis, though only a handful of patients have been treated so far and one MS researcher said far more study is needed before any victory is declared."
http://www.usatoday.com/news/health/2004-0 3-23-ms-chemo_x.htm

You would definitely have to talk to your doctor more about it though.