Human blood cells have been produced from embryonic stem cells, researchers said Monday.

Similar work has been done in mice, but the authors say this is the first time it's been done with human blood cells.

James Thomson led the research team from the University of Wisconsin-Madison. They produced the primitive human blood cells, which are known as hematopoietic precursor cells.

Red blood cells derived from human embryonic stem cells Courtesy PNAS

The discovery could lead to a new source of mature blood cells for transplants and transfusion, but the authors stress any clinical applications are likely years away.

The blood cells were developed from stem cells, which have the ability to transform themselves into more than 250 different cell types. Heart, muscle, brain and now blood are all potential final forms for stem cells.

So far, researchers have coaxed stem cells to become primitive blood cells in the laboratory.

The authors say the cells they developed "appear identical to those produced from human bone marrow cells." They hope to apply what they've learned to make new cells for transfusion and other therapies.

The study appears in the September 3 issue of the Proceedings of the National Academy of Sciences .