From Medical News Today:
According to two small studies published in the British Journal of Sports Medicine in April 2008, Tai Chi exercises can improve blood glucose levels and improve the control of type 2 diabetes and immune system response. […] After 12 weeks in the exercise program, the levels of glycated hemoglobin levels fell significantly, from 7.59% to 7.16% in diabetic patients, a significant difference. Interleukin-12, which boosts the immune response, increased in level; interleukin-4, which lessens the immune response, declined. In conjunction, T cell activity also significantly increased.
Tai Chi is a Chinese martial art that combines diaphragmatic breathing and relaxation with soft, gentle movements. It is considered moderate exercise, which has previously been shown to improve immune system response, in contrast to strenuous physical activity, which depresses it. Previous studies have shown that it improves respiratory and cardiovascular function, while improving flexibility and relieving stress.