Granulocyte factors as potential regulators of hemopoiesis. I. Localisation of hemopoietic activity within granulocytes.

Granulocytes stimulate GFU-S in lethally irradiated mice. A factor responsible for this stimulation was found to be contained within granulocyte granules. The factor is released from intact granulocytes during adherence. Granulocyte extract from adherent cells is devoid of this GFU-S-stimulatory activity. The obtained results indicate that factor inducing secretion of granule products indirectly affect hemopoiesis. This may be of particular importance in the course of inflammation.