The immunomodulatory mechanisms for acupuncture practice

Abstract

The system physiology approaches that emerge in western countries in recent years echo the holistic view of ancient Traditional Chinese Medicine (TCM) practices that deal with the root, rather than only the symptoms of diseases. Particularly, TCM practices, including acupuncture, emphasize the mobilization of self-healing mechanisms to bring back body homeostasis. Acupuncture has been practiced for over two thousand years to modulate body physiology via stimulation at specific body regions (acupoints). With the development of various research on acupuncture therapy, its regulatory effect on the immune system has been gradually recognized, especially on immunological diseases, including infectious and allergic diseases. In this study, we reviewed the immunomodulatory mechanism of acupuncture and systematically integrates existing research to respectively elucidate the modulatory mechanisms of acupuncture on the innate immune system, adaptive immune system, and well-known neuroanatomical mechanisms, including intact somatosensory-autonomic reflex pathway. With the advances made in recent systems physiology studies, we now have a great opportunity to gain insight into how acupuncture modulates immunity, and subsequently improves its efficacy.

Keywords: HPA axis; acupuncture; autonomic nervous system; immune system; neuro-immune regulation.

Figure 1

Acupuncture evoked pathways for modulating innate and adaptive immune responses. After acupuncture evoked a mechanical and thermal stimulus within acupoints, the generated electrical signal then transmitted by somatic sensory fibers to the central nervous system, and produced distinct descending regulatory pathways. Such as the cholinergic anti-inflammatory pathway, the vagal-adrenal pathway, the spinal-sympathetic pathway, and the brain-gut pathway. These pathways then to restoring the immune homeostasis by moderating innate (A) and adaptive (B) immune responses. (A) Acupuncture modulates the innate immune response by regulating innate immune cells’ activity and the capacity of release cytokines. The proliferation and differentiation of pro-inflammatory M1 macrophages can be blocked by acupuncture, whereas the number of anti-inflammatory M2 phenotypes is increased, along with the secretion of anti-inflammatory cytokines such as IL-10 and TNF-β. Acupuncture can regulate the quantity and activity of neutrophils and reverse the migration of neutrophils to the site of inflammation. NK cells can release cytotoxic granules containing perforin and granzyme to Lyse and kill abnormal cells, and acupuncture can increase the number and activity of NK cells. In the central nervous system, astrocytes and microglia can be modulated by acupuncture to reverse the activated state, and reduce the inflammatory responses. (B) Acupuncture primarily controls the adaptive immune system by controlling the development of T cells, which produces CD4⁺ T cells for humoral immunity and CD8⁺ T cells for antiviral immunity. The balance between pro-inflammatory Tregs and anti-inflammatory Th17, as well as between pro-inflammatory Th1 and anti-inflammatory Th2, is regulated by acupuncture. Maintaining the ratio of CD4⁺/CD8⁺ T cells while controlling the quantity and activity of CD8⁺ T cells will help the body’s immune homeostasis.