Stromal cell-derived factor-1 (SDF-1) is a member of the alpha (or C-X-C) family of chemokines. SDF-1 knockout mouse embryos had reduced B cell progenitors in liver and bone marrow, while myeloid progenitors are reduced only in the bone marrow. This demonstrates a fairly direct involvement of SDF-1 in hematopoiesis.
Aiuti et al. demonstrated that SDF-1 was a chemoattractant for hematopoietic stem cells (CD34 cells). It was four times more effective with bone-marrow stem cells than with stem cells isolated from peripheral blood, suggesting a possible explanation for the apparent selective release of stem cells from the marrow. This in vitro response to SDF-1 is enhanced by IL-3.
The implication of this study is that stromal bone marrow cells release a factor that attracts certain stem cells and, possibly, that restricts their mobility until migration is appropriate. These results are especially interesting for two reasons. First, they clearly demonstrate an effect of chemokines on something other than an immune response. Second, they may have a profound impact on efforts to improve the mobilization of stem cells for transplantation and for the engraftment of stem cells after transplantation.