Production of hematopoietic stem cell-chemotactic factor by bone marrow stromal cells

Chemotactic factors produced by stromal cells in the bone marrow are characterized. Two kinds of factors produced by stromal cell lines are identified using blind-well Boyden's Chambers; one is a neutrophil- chemotactic factor and the other a hematopoietic stem cell (HSC)- chemotactic factor. The latter attracts blastic cells in a low-density fraction, which are Thy1lo, wheat germ agglutinin (WGA)hi, H-2Khi, Ly-1- , Ly-2-, L3T4-, Ly5-, and slg-. The molecular weight of this HSC- chemotactic factor is estimated to be more than 200 kD. Putative cytokines and growth factors, such as granulocyte colony-stimulating factor (CSF), macrophage CSF, granulocyte-macrophage CSF, stem cell factor (SCF), interleukin (IL)-6, and IL-3, do not possess HSC- chemotactic activity. These findings strongly suggest that bone marrow stromal cells produce a new factor that attracts HSCs.