Immune Responses to Spinal Manipulation
SOURCE: Dynamic Chiropractic ~ May 6, 2011
By Malik Slosberg, DC, MS
For many years, chiropractors have observed in their own practices that their patients sometimes demonstrate improvements of complaints related to immune problems: the disappearance or lessening of allergy symptoms, quicker recovery from or less frequent and severe colds and other respiratory infections, and so on.
In the scientific literature, there have been occasional case reports that corroborate such findings, but no sound evidence to really document their veracity. These clinical observations remain suspended in that grey area unsubstantiated by scientific data to confirm their validity. Significant limitations of changes attributed to spinal manipulation in individual patients include
2) there is no blinding;
3) the improvement may simply be due to time;
4) they may be a nonspecific effect of care and attention;
5) it may be a regression to the mean; or
6) the result may be due to something other than spinal manipulation.
In some large studies, it has been found that chiropractic care for nonmusculoskeletal conditions is only weakly to moderately successful, but rarely harmful. [1-2] The most recent and thorough systematic literature review found that the evidence for effectiveness of spinal manipulation was inconclusive for nonmusculoskeletal conditions. 
Despite the lack of evidence of clinical effectiveness for nonmusculoskeletal conditions, a series of recent studies from several international research groups is systematically building the case that spinal manipulation appears to reduce the production of pro-inflammatory cytokines and increase the blood levels of immunoregulatory cytokines. Cytokines are small cell-signaling protein molecules that are secreted by numerous cells of the immune system and are a category of signaling molecules used extensively in intercellular communication.
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The accumulation of data from these studies suggests that a possible benefit of spinal manipulation is related to neuroimmunological effects. Of course, this is an exciting proposition for clinicians who have seen such changes in their own patients. Let’s review some of the research exploring the connections between spinal manipulation and functional changes in the immune system.
Early Research on Manipulation and the Immune System
Research in the 1990s laid the groundwork for the more recent papers published in the past five years. Brennan, et al.,  published a paper demonstrating that upper thoracic spinal manipulation resulted in markers indicating significant increased phagocytic activity of neutrophils and monocytes compared to a sham manipulation or soft-tissue treatment. The findings suggest that a certain force threshold was needed to elicit the response.
In a second study, Brennan, et al.,  concluded that their data suggests spinal manipulation, which generates a force over a certain threshold, elicits viscerosomatic responses that affect both neutrophils and mononuclear cells phagocytic activity, at least over the short term. And in a very small 1994 study,  the study authors concluded that upper cervical adjustments increased CD4 “helper” T-cell counts, which initiate the body’s response to viruses in HIV-positive subjects, by 48 percent over the six-month duration of the study.
Neural immunoregulation: Communication Between the Immune and Nervous Systems
These earlier papers have now been followed-up by a series of recent studies within the past five years. Teodorczyk-Injeyan, et al.,  described the interplay between the nervous system and immune system as neural immunoregulation. The authors note that immune homeostasis is based on the reciprocal communication between the immune and the nervous systems executed by the actions of cytokines and neurotransmitters. In addition, the paper explains the close association of autonomic nerve terminals with macrophages and lymphocytes, which facilitates a chemically mediated transmission between nerves and immune cells.
This research group has published a series of papers that explores the relationship of spinal manipulation, spinoautonomic reflexes and their influence on activity of cells involved in immune and/or inflammatory responses. These interconnections may have great clinical relevance because studies  on the pathophysiology of discogenic low back pain, sciatica, and ligamentous tissue damage-related pain  reveal that the production of pro-inflammatory mediators, such as tumor necrosis factor alpha (TNF-a) and interleukin-1 beta (IL-1ß), are major factors in the genesis of pain and functional changes in neural activity. Furthermore, studies of the hypoalgesic effects of spinal manipulation have already been reported in the literature, suggesting that an anti-inflammatory mechanism might be activated by spinal manipulation. [10-11] Recent clinical studies have shown that chemical blockage of TNF-a is highly effective in reducing sciatic pain. 
Reduced Pro-Inflammatory Cytokines After Spinal Manipulation