FLT3 ligand levels. (A) FL levels were determined with an enzyme-linked immunosorbent assay using plasma samples obtained at the aplasia and outcome assessments. The individual results are plotted, with solid lines indicating the mean level for each group. (B) The effect of FL on the FLT3 inhibitory activity of lestaurtinib. TF/ITD cells, expressing ITD-mutated FLT3, were incubated in plasma containing increasing concentrations of lestaurtinib in the presence or absence of 1000 pg/mL FL. After immunoprecipitation for FLT3 and electrophoresis, the blots were probed with antiphosphotyrosine (top blot), and then stripped and reprobed for total FLT3 (bottom blot).