Enhancement of in vitro interleukin-2 production in normal subjects following a single spinal manipulative treatment

Abstract

Background: Increasing evidence supports somato-visceral effects of manual therapies. We have previously demonstrated that a single spinal manipulative treatment (SMT) accompanied by audible release has an inhibitory effect on the production of proinflammatory cytokines in asymptomatic subjects. The purpose of this study is to report on SMT-related changes in the production of the immunoregulatory cytokine interleukin 2 (IL-2) and to investigate whether such changes might differ with respect to the treatment approach related to the presence or absence of an audible release (joint cavitation).

Methods: Of 76 asymptomatic subjects, 29 received SMT with cavitation (SMT-C), 23 were treated with SMT without cavitation (SMT-NC) and 24 comprised the venipuncture control (VC) group. The SMT-C and SMT-NC subjects received a single, similar force high velocity low amplitude manipulation, in the upper thoracic spine. However, in SMT-NC subjects, positioning and line of drive were not conducive to cavitation. Blood and serum samples were obtained before and then at 20 and 120 min post-intervention. The production of IL-2 in peripheral blood mononuclear cell cultures was induced by activation for 48 hr with Staphylococcal protein A (SPA) and, in parallel preparations, with the combination of phorbol ester (TPA) and calcium ionophore. The levels of IL-2 in culture supernatants and serum were assessed by specific immunoassays.

Results: Compared with VC and their respective baselines, SPA-induced secretion of IL-2 increased significantly in cultures established from both SMT-C and SMT-NC subjects at 20 min post-intervention. At 2 hr post-treatment, significant elevation of IL-2 synthesis was still apparent in preparations from SMT-treated groups though it became somewhat attenuated in SMT-NC subjects. Conversely, IL-2 synthesis induced by TPA and calcium ionophore was unaltered by either type of SMT and was comparable to that in VC group at all time points. No significant alterations in serum-associated IL-2 levels were observed in any of the study groups.

Conclusion: The present study demonstrates that, the in vitro T lymphocyte response to a conventional mitogen (SPA), as measured by IL-2 synthesis, can become enhanced following SMT. Furthermore, within a period of time following the manipulative intervention, this effect may be independent of joint cavitation. Thus the results of this study suggest that, under certain physiological conditions, SMT might influence IL-2-regulated biological responses.

Figure 1

SPA-induced IL-2 secretion in cultures established 20 minutes (A) and 2 hours (B) post-intervention (PI). PBMC cultures were activated with SPA (10 μg/ml) at initiation and incubated at 37°C for 48 hr. The concentration of IL-2 (pg/ml) produced in vitro by cells from a subject at 20 min (A) and 2 hr (B) post intervention is plotted against the concentration of IL-2 produced at baseline by the same subject. Each point represents a subject for whom a complete set of data was available. Comparison of best fit lines revealed statistically significant differences between SMT-C (spinal manipulative therapy with cavitation, n = 26) and VC (venipuncture, n = 21) as well as SMT-NC (spinal manipulative therapy without cavitation, n = 23) and VC both for 20 min and 2 hr post intervention (see text for details).

Figure 2

Phorbol ester (TPA)-induced IL-2 secretion in PBMC cultures established 20 minutes (A) and 2 hours (B) post-intervention (PI). PBMC cultures were activated with the combination of TPA (3 × 10^-8 M) and calcium ionophore A23187 (200 ng/ml) at initiation and incubated at 37°C for 48 hr. IL-2 levels were determined in culture supernatants by specific ELISA. Each point represents the concentration of IL-2 (ng/ml) produced in vitro by cells from a subject at 20 min (A) and 2 hr (B) post intervention plotted against the concentration of IL-2 produced at baseline by the same subject. Each point represents a subject for whom a complete set of data was available. Comparison of best fit lines revealed no statistically significant differences between SMT-C (spinal manipulative therapy with cavitation, n = 22) and VC (venipuncture, n = 16) as well as SMT-NC (spinal manipulative therapy without cavitation, n = 17) and VC both for 20 min and 2 hr post intervention (see text for details).