Effect of conditioned media of acute myeloid leukemia blast cells on complement synthesis by cultured human cells of monocyte and hepatocyte origin.

The effect of conditioned media of 3-day cultures of blast cells from peripheral blood of 5 patients with acute myeloid leukemia (CM-AML) was studied on the synthesis of C2, factor B (Bf) and C1 esterase inhibitor (C1-INH) by human monocyte-macrophage cultures and HepG2 hepatoma cell line. The level of C2 in the culture supernatants was measured by immune hemolysis, those of Bf and C1-INH by ELISA. CM-AML was added to the monocyte cultures on day 3 and replaced by culture fluid on day 6. Compared to the control cultures, CM-AML significantly increased C2 and Bf levels and slightly decreased C1-INH levels in the culture fluids on day 6. On day 9, Bf synthesis enhancement still could be observed but C2 and C1-INH levels did not significantly differ from those of the control. CM-AML significantly increased the synthesis of factor B by the HepG2 cells too. A strong correlation was found between the results of the Bf protein and RNA determinations, which means that the supernatants of AML blasts affect the gene expression of factor B at a pretranslational level. The selective complement synthesis modifying effect of CM-AML was not due to interferons (IFN) because neither IFN-alpha nor IFN-gamma could be detected in these conditioned media. The present findings indicate that the hypercomplementemia observed in AML patients can be due to unknown factor(s) produced by leukemic blast cells.