The body's lifelong guardians, grown in a dish: stem cells replay the immune system's first chapter

Every organ you own is patrolled by guardian immune cells that arrive before you are born and then stay for decades — microglia nursing the brain, Kupffer cells filtering the liver. Because they are born in embryonic tissue no one can ethically watch, scientists have never seen them begin. Now a team at Belgium's Flanders Institute for Biotechnology, led by Renzo Mancuso and Bart De Strooper and published in Developmental Cell, has replayed that chapter in a dish: human stem cells coaxed to mimic the yolk sac produced the very progenitors that seed those guardians. Transplanted into mice, the cells settled in brain, liver, heart and kidney and took on each organ's identity — and the youngest progenitors took root best. It is a new window on diseases from Alzheimer's to fibrosis, and a first sketch of how damaged guardians might one day be replaced.

SDG 9 · Industry, innovation and infrastructure — Mechanism: tech innovation