The effect of acupuncture on the immune system has been investigated by Japanese researchers. They measured immune system markers in the blood of seventeen healthy volunteers aged 21-51, both before and after receiving acupuncture, in order to determine the activity of T cells, B cells, macrophages and natural killer cells. Their observations suggested that acupuncture regulates the immune system, and promotes humoral (antibody driven) and cell-mediated (T cell driven) immunity, as well as natural killer cell activity.
(Acupuncture Regulates Leukocyte Subpopulations in Human Peripheral Blood. Evidence-Based Complementary & Alternative Medicine, December 2007.)