Blood Stem Cells Fight Invaders

The blood stem cells, which are scattered sparingly throughout the marrow and capable of replenishing an entire blood system, are the most understood stem cells and have allowed for successful bone marrow transplants. Scientists previously thought that this hematopoietic stem cell had a singular role but research from a professor at Harvard has shown that its role is far more versatile.

They studied lymph samples from the thoracic ducts of mice and found that there was a population of cells that behaved identically to blood stem cells and upon further tests found these cells present in visceral organs also. It was discovered that hematopoietic stem cells can travel from the bone marrow into the blood circulation and enter visceral organs and play a role in the immune system. When the cells encountered invaders, they divided and made new immune system cells such as leukocytes. After a period of time, the cells would then be taken up by the thoracic duct and reenter the circulation then back to the marrow. Due to the presence of endotoxin, some cells would get stuck in the tissue and would be triggered to proliferate into immune cells. Overall the hematopoietic stem cells seem to play a rolein sensing local environmental disturbances and initiating an immune response. This research opened new doors for looking into how our bodies fight pathogens and ways diseases may use this same process.

http://www.sciencedaily.com/releases/2007/11/071129121143.htm