Figure 9: Effects of β2-ARs stimulation on cytokine profiles and Th 1 and Th17 cell differentiation. The SNS regulates the differentiation of Th0 cells to Th17 and Treg cells, in part by modulating levels of IL-2. A) NE released from sympathetic nerves bind β2-ARs expressed in naïve Th cells. Activation of Th0 cell β2-ARs reduces the production of IL-2. IL-2 exerts an inhibitory effect on Th17 cell differentiation from naïve Th0. However, IL-2 does promote the clonal expansion of Th17 once these cells develop. By suppressing IL-2 production, the SNS is expected to promote Th17 cell differentiation, but inhibit clonal expansion of the Th17 cells once differentiated. B) Activation of β2-ARs in APCs and Th0 cells reduces their production of IL-2. Since IL-2 promotes the differentiation of Treg cells, and is required for their suppressor functions, SNS suppression of IL-2 production is anticipated to inhibit Treg cell differentiation and their suppressor functions. C) Stimulation of β2-ARs on dendritic cells (DC) that have been co-stimulated with a TLR2 and a NOD-like receptor agonist skews the immune response away from a Th1-type response but towards a Th17 response based by increasing DC production of IL-6 and reducing DC production of IL-12, without changes in IL-23. (Green arrows, excitatory; red arrows, inhibitory).