Environment for infection-fighting cells.

• Position: Bone Marrow

There now is a deeper understanding of the environment within bone marrow that nurtures stem cells. The biological setting for specialized blood-forming cells that produce the infection-fighting white blood cells known as T cells and B cells has been identified by scientists at the Children's Medical Research Center, Dallas, Texas.

It was found that cells called early lymphoid progenitors, which are responsible for producing T cells and B cells, thrive in an environment known as an osteoblastic niche. The investigation, published in Nature and led by Sean Morrison, also establishes a promising approach for mapping the entire blood-forming system.

Scientists already know how to manufacture large quantities of stem cells that give rise to the nervous system, skin, and other tissues, but they have been unable to make blood-forming stem cells in a laboratory, in part because of a lack of understanding about the niche in which they and other progenitor cells reside in the body.

"We believe this research moves us one step closer toward the development of cell therapies in the blood-forming system that don't exist today," reports Morrison, director of CMRC. "In understanding the environments for blood-forming...