Lymphohematopoietic development from embryonic stem cells in vitro.

Differentiation induction from embryonic stem (ES) cells to blood cells is one of the best systems to study the molecular mechanisms which are involved in the development and differentiation of lymphohematopoietic cells. Several systems including our new system (OP9 system) using a macrophage colony stimulating factor-deficient stromal cell line named OP9 are discussed in this paper. It is advantageous that the OP9 system does not require any exogenous growth factors or a complex embryoid structure for the induction. The OP9 system combined with genetic manipulation of ES cells should facilitate to elucidate molecular mechanisms during development and differentiation of blood cells including B-lineage cells.