I doubt it will do any harm. In fact it may help.
Personally I run alot, have done several marathons, and have found that excersise helps in many, many ways. For one it may even regulate the immune system a bit. Keeps you sane. Keeps you other wise healthy.
I would run still. Keep an eye on your iron levels. If you have UC they could be low and it is vital, especially if you are excersising regularly to avoid low iron and anemia.