Stromal cell exposure inhibits megakaryocytic differentiation in primary human stem cells.

Primary human hematopoietic stem cells were cultured 7 days with either IL-3 plus SCF to expand myeloid progenitors or with TPO plus SCF plus IDB to induce megakaryocytic differentiation. Cells were either cultured alone or on a monolayer of primary human bone marrow stromal cells. Cells treated as indicated were stained with PE–anti-CD41a (HIP8-PE) or isotype-matched control antibodies and analyzed by single-color flow cytometry. Log fluorescence intensity is indicated on the x-axis. Original magnification, × 500.