[Humoral regulation of human granulocytopoiesis and monocytopoiesis]

Abstract

The mechanisms which regulate cellular differentiation from human pluripotent stem cells to the committed granulocytic and monocytic stem cells (CFU-D, CFU-C) are still imperfectly understood. Most studies involve in vitro and animal experimentations and the relevance of the conclusions on human in vivo mechanisms may be questionable. The monocyte-macrophage system figures actually as the major source of humoral regulators of the normal granulocytopoiesis and monocytopoiesis in man. It produces CSF, a family of glycoproteins which stimulate the proliferation and maturation of CFU-c, and PGE which are inhibitory. In addition, CSF may act as a stimulator of the proliferation and myeloid commitment of CFU-S. Several other humoral factors are of less well established importance. Bacterial toxins and antigens are potent stimulators of the production of CSF. Androgens are stimulators of the proliferation of CFU-C. Lactoferrin, a glycoprotein released by granulocytes, may inhibit CSF production by monocytes-macrophages. CIF, a group of lipoproteins, may act as an inactivator of CSF. Granulocyte chalones and interferon may be inhibitors, though poorly specific, of granulopoietic differentiation. Glucocorticoids may exert an inhibitory effect on CFU-C proliferation and CSF release. Precise analysis of the humoral regulation of normal granulocytopoiesis and monocytopoiesis in man seems to be of critical interest in understanding the pathophysiological mechanisms of blood diseases such as leukemias and aplastic anemias.