Cell lineages in haemopoiesis: comments on their regulation.

The regulation of cell production and the determination of cell lineage in haemopoiesis are the result of multiple processes involving cell-cell interactions and the action of specific haemopoietic growth factors as well as other cytokines. Additive and synergistic interactions between these factors, and also with those involved in the regulation of lymphopoiesis have been described, which involve modulation of the growth and differentiation of haematopoietic precursors. However, the mechanisms which determine the self-renewal and the differentiation of the pluripotent lymphohaemopoietic stem cell remain largely undefined.