The autonomic inflammatory reflex

Immune challenges are detected by the CNS, which then activates a sympathetic nerve pathway whose function is to dampen down the systemic inflammatory response to the immune challenge, in negative feedback manner. The afferent pathways whereby the CNS is informed of the immune challenge may be humoral and/or neural, but are not fully defined. The efferent pathway of the inflammatory reflex is in the splanchnic sympathetic nerves. Its antiinflammatory actions are mediated by several abdominal viscera, not just the spleen. When activated by systemic immune challenge, the reflex suppresses proinflammatory cytokine responses while enhancing antiinflammatory cytokine release. This reflex action is powerful, and can strongly influence the outcome of systemic bacterial infection. It appears to be a basic biological phenomenon that transcends species. Its full implications remain to be worked out.