My immune system has in general improved since I've been on T, but I don't know if I could say it is entirely related to that. I've made a lot of effort to get healthier overall since starting to transition, so I can't definitively say that the improvements aren't from that.
I got a little fatigued when I first got on T. I'm a little fatigued now, but my doctor thinks that's because my T levels were too high post-hysto. So we're dropping my dose by 20% to see if that helps. I don't think it's any kind of illness or depression.
In general, I usually get sick twice a year when it starts to get cold, and then when it starts to warm up. When I would get really sick, I would usually be down for a week. Now, it's 48-72 hours, tops.