PLASMA SERUM LEVELS OF FLT3 LIGAND ARE LOW IN NORMAL INDIVIDUALS AND HIGHLY ELEVATED IN PATIENTS WITH FANCONI-ANEMIA AND ACQUIRED APLASTIC-ANEMIA/

The flt3 ligand is a growth factor that stimulates the proliferation o f hematopoietic progenitor and stem cells. We established a sensitive enzyme-linked immunosorbent assay (ELISA) to measure the concentration of flt3 ligand in plasma or serum from normal individuals, as well as in patients with hematopoietic disorders. Concentrations of flt3 liga nd in plasma or serum from normal individuals were quite low: only 12% (7 of 60) of normal individuals had flt3 ligand levels above 100 pg/m L (the limit of detection). In contrast, 86% (19 of 22) of samples fro m patients with Fanconi anemia and 100% (eight of eight) of samples fr om patients with acquired aplastic anemia had plasma or serum levels a bove 100 pg/mt. Mean plasma or serum concentrations (calculated by ass igning a value of 0 pg/mL to any sample reading below the level of det ection) were as follows: normal volunteers, 14 pg/mL; patients with Fa nconi anemia, 1,331 pg/mL; and patients with acquired aplastic anemia, 460 pg/mL. Concentrations of flt3 ligand in blood are, therefore, spe cifically elevated to a level that may be physiologically relevant in hematopoietic disorders with a suspected stem cell component. The elev ated flt3 ligand concentrations in these individuals may be part of a compensatory hematopoietic response to boost the level of progenitor c ells. (C) 1995 by The American Society of Hematology.