14.4 Making and Recycling Red Cells

The Story

If you tested Stina’s ability to make red cellsThe basic structural and functional units of life. in isolation, it would look fine: her marrow responds, her spleen recycles, the assembly line runs. That is what makes her anemia so frustrating to the clinicians who keep handing her iron. The factory isn’t broken. The supply chain is being deliberately interrupted upstream, and you can’t see where until you know how the cycle is supposed to run.

Red cells are made on demand. When blood oxygen drops, the kidney releases erythropoietin(EPO): A hormone produced by the kidneys that stimulates erythropoiesis. (EPO), the marrow ramps up production, and each new red cell fills with hemoglobinThe oxygen-carrying protein in red blood cells that gives blood its red color. and ejects its nucleusThe control center of the cell that contains DNA and directs cellular activities. to make room for oxygen cargo. After about 120 days the worn-out cell is retired in the spleen and liver, where its hemoglobin is broken down and — crucially — its iron is recycled back for the next batch. This recycling loop is exactly where chronic inflammation jams the works: by locking iron away in storage, it starves the marrow of the raw material it needs, even while plenty of iron sits in the body. Stina’s erythropoiesisThe process of red blood cell production. isn’t failing; it is being rationed.

From Stina’s chart: Stina’s marrow can make red cells, and her spleen can recycle them — the machinery works. The problem lives in the raw material that chronic inflammation hides