Action of inhibitor released from neutrophils and leukemic blast cells.

The concept that polymorphonuclear leukocytes, or neutrophils, play a role in feedback control of granulopoiesis has been supported by the finding in bone marrow culture studies that mature neutrophils inhibited formation of granulocytic colonies. The study described in this paper was done to investigate the mechanisms involved. With the use of a modified assay it was found that mature neutrophils released factors that reduced the proliferation of colony-forming cells in cultures stimulated by cell-free colony-stimulating factor. In myeloproliferative and myelodysplastic disorders the amount of inhibitor released by the neutrophils varied greatly. Leukemic blast cells also released inhibitor, and in some cases the amount released per cell was greater than the amount released from normal mature neutrophils. The inhibitory factors released from the neutrophils differed from those previously described in the literature in terms of mode of action and apparent molecular size.