Neutralization of TPO impairs the capacity of stromal cells to support the generation of megakaryocyte progenitors.

CD34⁺ progenitors were cocultured 12 days with ECs with 10% supernatant of nontransfected COS cells (mock) or with 10% supernatant of CD40L-CD8α–transfected COS cells (CD40L) in the presence (+) or not of a neutralizing anti-TPO antibody (anti-TPO). Cells were then assayed for the presence of CD41 megakaryocyte-specific lineage marker by flow cytometry.