Japanese researchers have investigated the effect of acupuncture on the human immune system. They measured CD-positive cell counts and cytokine expression levels in the peripheral blood of fifteen healthy volunteers before and after acupuncture, to determine the activity of T cells, B cells, macrophages and natural killer (NK) cells. There was a statistically significant increase in the number of CD2(+), CD4(+), CD8(+), CD11b(+), CD16(+), CD19(+), CD56(+) cells as well as IL-4, IL-1beta and IFN-gamma levels in the cells after stimulation of acupuncture points. These observations indicate that acupuncture may regulate the immune system and promote the activities of humoral and cellular immunity as well as NK cell activity. (Acupuncture Regulates Leukocyte Subpopulations in Human Peripheral Blood. Evid Based Complement Alternat Med. 2007 Dec;4(4):447-453).