Acupuncture stimulation enhances splenic natural killer cell cytotoxicity in rats

Acupuncture stimulation of the anterior tibial muscle, which is equivalent to Tsu-sanli point (S36) stimulation and which induces acupuncture analgesia, enhanced YAC-1 cell lytic activity of the splenic natural killer cells (NK activity) from pentobarbital anaesthetized Wistar rats. On the other hand, abdominal muscle stimulation, which does not induce acupuncture analgesia, did not affect NK activity. The serum from rats treated with acupuncture stimulation (acupuncture-stimulated rats) also enhanced the NK activity of other intact rats. The reinforcement effect of serum remained after heat inactivation (56 degrees C, 30 min). The serum from acupuncture-stimulated rats also had more potent complement activity than that from control rats. These results indicate the following considerations: 1) the Tsu-sanli point may be one of the specific points modulating immune activity, 2) this immune modulation system may share a common nervous pathway with the acupuncture analgesia-producing system, 3) acupuncture stimulation may modify NK activity through unknown heat stable humoral factors as well as the nervous system, and 4) acupuncture stimulation may activate the complement system.