I've been a competitive swimmer nearly my whole life and I've been in remission from UC for nearly 4 months after being in two flares over the past year. I feel like I'm ready to get back into hard training now that I'm "out of the woods", at least for now. I just started Remicade this month and was also worried about whether a lot of exercise could be detrimental while on an immunosuppresant. I did some research and the most inspiring thing I found was learning about David Garrard's battle with Crohn's: http://www.ccfa.org/about/news/garrard
He is currently on Remicade and is a starting quarterback for the Jaguars. That was proof enough for me that a tough workout plan can be accomplished while on an immunosuppresant!
BUT, since you are just coming out of a very long flare I would take it easy when starting to workout again. When I started back into swimming I took things very S-L-O-W-L-Y. I started at about 15% of my normal training volume and was very cautious when adding any more workouts. Your body sure has been through a lot in the past 8 months so take that into account and listen to how you feel. But I was so much happier when I started to swim again, I'm sure you'll feel the same too! Good luck!