Researchers have developed a line immortal stem cells that allow them to generate an unlimited supply of artificial red blood cells on demand. If these artificial blood cells pass clinical trials, they'll be far more efficient for medical use than current red blood cell products, which have to be generated from donor blood and would be a huge deal for patients with rare blood types, who often struggle to find matching blood donors. The idea isn't for these immortal stem cells to replace blood donation altogether - when it comes to regular blood transfusions, donated blood still does the trick.

But it's a constant struggle to propagate red blood cells from donor blood. In the UK alone, 1.5 million units of blood need to be collected each year to meet the needs of patients, particularly those with rare blood types of conditions such as sickle-cell disease. The lead researcher Jan Frayne…