If you’re interested, I have put a number of articles on to the tai chi website here which discuss those benefits, particularly in relation to the immune system. This is only a few though, and by searching for something along the lines of ‘medical research in tai chi (or qigong) and the immune system’, I’m sure you will come up with many more.
If you haven’t already seen it, you might also enjoy this.
James Drewe teaches Taijiquan and qigong in both London and in Kent. Details of weekly classes can be found on the website, and there are classes for 2-person Taijiquan on one Saturday a month.
Phone: 07836-710281 or 020-8883 3308