Vagal Paraganglia Bind Biotinylated Interleukin-1 Receptor Antagonist: A Possible Mechanism for Immune-to-Brain Communication

Interleukin-1 β is a proinflammatory cytokine released by activated immune cells. In addition to orchestrating immune responses to infection, interleukin-1 β is a key mediator of immune-to-brain communication. Interleukin-1 β and endotoxin (which releases IL1 β from immune cells) cause centrally mediated illness responses such as fever, aphagia, etc. These effects are blocked by intraperitoneal IL1 receptor antagonist (IL1ra), suggesting critical involvement of peripheral IL1 receptors. Centrally mediated illness responses are also blocked by vagotomy, suggesting that IL1 β directly or indirectly activates vagal afferents. To test for IL1 β binding, whole vagus (abdominal, laryngeal, and thoracic) and sections of hepatic vagus and liver hilus were incubated with biotinylated IL1ra and processed for avidin-biotin complex (ABC) or avidin-FITC histochemistry. Glomus cells of vagal paraganglia were labeled in all regions of the vagus. Biotinylated IL1ra also labeled smooth muscle and endothelial cells of blood vessels and lymphoid tissues. No label was present in omission or competition controls. These data suggest that centrally mediated illness responses result from IL1 activation of vagal paraganglia.