Overexpression of bcl-2 in transient abnormal myelopoiesis associated with Down syndrome

Transient abnormal myelopoiesis (TAM) is a haematological complication found in Down syndrome. To determine the mechanisms of sustained proliferation of TAM cells, we studied the expression of apoptosis-related proteins, such as bcl-2, Fas (APO-1/CD95) and p-53, in peripheral blood cells from a new-born infant with Down syndrome and TAM. Using flow cytometry, peripheral blood mononuclear cells (PBMCs), consisting mostly of blast cells, showed marked expression of bcl-2 protein but not of Fas or p-53 products. DNA gel electrophoresis of PBMCs, cultured in the absence of serum factors, revealed no marked fragmentation. Our findings suggest that bcl-2 overexpression may be associated with prolonged cell survival of TAM cells.