Hematopoietic Stem Cells Patrolling The Body for Danger

Boston, MA -

A potentially new role for stem cells has been described. In most cases, various stem cells such as mesenchymal stem cells as well as hematopoietic stem cells possess immune suppressive characteristics. In a recent publication (Massberg et al. Immunosurveillance by Hematopoietic Progenitor Cells Trafficking through Blood, Lymph, and Peripheral Tissues. Cell. 2007 Nov 30;131(5):994-1008) it was demonstrated that hematopoietic stem cells may actually comprise an arm of the immune system.

The researchers found that hematopoietic stem cells may be extracted from lymphatic tissue, and that the cells leave the bone marrow, circulate in the lymph nodes and then go back into the bone marrow.

Interestingly, these hematopoietic stem cells have toll like receptors on them and upon activation they differentiate into dendritic cells. This paper is very interesting since toll like receptor activation has been demonstrated to make mesenchymal stem cells lose immune suppressive properties.