Hairy cell leukemia: defective production of granulocyte-macrophage colony-stimulating factor by peripheral blood cells.

: Granulocyte-macrophage colony-stimulating factor (GM-CSF) production by the peripheral blood (PB) cells of hairy cell leukemia (HCL) patients whose PB contained only 2 to 10% hairy cells was studied in an in vitro bone marrow culture system. In addition, the possible inhibitory effect on the growth of normal granulocyte-macrophage colony-forming cells (GM-CFC) by the patients' mononuclear cells or serum was assayed. GM-CSF production by PB cells of HCL patients was 82 +/- 18% (mean +/- sd) lower than its production by normal PB cells. No significant inhibition of normal GM-CFC growth was observed in the presence of patients' PB mononuclear cells or their serum. These findings suggest that in HCL patients the monocyte-macrophage system is defective in its capacity to produce GM-CSF. This defect may play a role in the impaired granulocyte production known to occur in HCL.