14.7 The Acute-Phase Alarm

The Story

Here, finally, is why the iron pills never worked. Every time Stina’s disease flares, IL-6 reaches her liver and triggers an emergency broadcast: the liver pours out acute-phase proteinsLarge molecules made of amino acids with various functions in the body.. One of them, hepcidin, acts like a vault door slamming shut on iron — pulling it out of circulation and locking it in storage, starving the marrow even though her body holds plenty. The same alarm that drives her anemia also churns out a protein that will matter far more later: serum amyloid A.

The acute-phase response is the liver’s rapid-reaction program. Driven largely by IL-6, the liver ramps up proteins including C-reactive protein (CRP) — a familiar inflammation marker — and serum amyloid A (SAA), and it raises hepcidin, the master iron regulator. Hepcidin traps iron inside storage cellsThe basic structural and functional units of life. so it can’t reach the marrow; the result is anemia of chronic inflammation, Stina’s stubborn, iron-refractory anemia. The danger is in the SAA. A single flare’s worth is harmless, but SAA churned out year after year is the raw material that can misfold and deposit as AA amyloid in tissues. Stina’s decades of unbroken inflammation have been quietly supplying that raw material — a slow fuse this module lights and the digestive and urinary modules will see detonate.

From Stina’s chart: When inflammation strikes, Stina’s liver floods her blood with acute-phase proteins — CRP and, crucially, serum amyloid A (SAA) — while IL-6 drives hepcidin to lock her iron away.