How the brain talks to the immune system This diagram shows the inflammatory reflex - a neural circuit where the brain regulates inflammation through the vagus nerve. It’s how psychological stress, inflammation, and immune activity stay linked. 1️⃣ The signal starts in the brain The vagus nerve carries electrical impulses from the brainstem to the spleen, the body’s blood-filtering and immune-coordinating organ. 🟢 Example: Deep breathing and meditation can activate the vagus nerve, lowering heart rate and reducing circulating inflammatory markers like CRP and IL-6. 2️⃣ The spleen acts as a relay When the vagus nerve is stimulated, it triggers the splenic nerve to release noradrenaline, which activates immune T cells to release acetylcholine. 🟢 Example: In animal models, vagus nerve stimulation increased noradrenaline in the spleen within minutes, showing how fast the nervous system can modulate immunity. 3️⃣ Acetylcholine calms inflammation This neurotransmitter binds to receptors on macrophages, reducing the release of tumor necrosis factor-α (TNF-α), an inflammatory cytokine involved in chronic disease. 🟢 Example: Clinical studies using implanted vagus nerve stimulators in rheumatoid arthritis patients lowered TNF-α levels and improved joint pain without immunosuppressive drugs. The inflammatory reflex shows that inflammation isn’t just chemical, it’s electrical. The brain can literally tell the immune system when to stand down.