SERUM STEM-CELL FACTOR LEVELS IN PATIENTS WITH APLASTIC-ANEMIA

Immune suppression of hematopoiesis has been implicated in the pathoge nesis of acquired aplastic anemia. Similarly, abnormalities of T cells and bone marrow stromal cells have been reported in aplastic anemia, as has abnormal cytokine production. Stem cell factor (SCF) (also know n as kit ligand, mast cell growth factor and Steel factor) is an early acting hematopoietic growth factor that is produced by a variety of m esenchymal cells including bone marrow stromal cells. To determine whe ther abnormalities in the production of stem cell factor occur in apla stic anemia, we evaluated serum levels of SCF in 25 patients with apla stic anemia. The mean serum levels of SCF in aplastic anemia patients were significantly lower (2.7 +/- 1.1 ng/ml) than those found in a com parable population of 257 normal controls (3.3 +/- 1.1 ng/ml) (P = 0.0 11), The SCF level did not correlate with patient age, the duration of aplastic anemia or with white blood cell count, platelet count or hem atocrit. Although there is no direct evidence that lower SCF serum lev els contribute to the pancytopenia seen in this disorder, identificati on of underlying abnormalities that can result in the deficient produc tion of stromally derived hematopoietic growth factors will be importa nt.