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).