To be honest, I'm not sure about RA compromising your immune system - I don't have a medical degree. In the past, before started immunosuppressant drugs for my RA, I did take extra precautions not to get sick (e.g., train family and friends to stay away from me when they were ill) in retrospect, that wasn't so much because I picked up illnesses quicker or they were more severe than healthy people, but because when I was sick, my RA would usually flare. However, given that RA and MS are both autoimmune diseases and cancer impacts the immune system... it's hard to say what's the chicken and what's the egg.

There does seem to be an impact on the heart when you have RA, which comes with an increased risk of heart attack and stroke, although I would suspect that if your case of RA is mild to moderate, you eat a healthy, balanced diet and stay in shape, you may be able to largely negate that. Of course, I may have mentioned I'm not a doctor and have no facts to back that up, just than common sense. For more expert advice, I'd suggest you talk to your doctor.