Micrographic pictures of megakaryocytic cells obtained from liquid culture of umbilical cord blood MNCs. Cells were cultured for 8 days in the presence of 10 ng/mL rhTPO and either control or ITP plasma. (A) Wright staining of a cytocentrifugation slide with cells from culture containing control plasma. Morphologically recognizable megakaryocytic cells at various stages of development were observed. Macrophage-like cells and small lymphocytes were the only major contaminating cells. Original magnification, × 400. (B) Immunohistochemistry staining (CD41, mAb 5B12) of cells from culture containing control plasma. Megakaryocytic cells are stained red. Original magnification, × 200. (C) Immunohistochemistry staining (CD41, mAb 5B12) of cells from culture containing group IIb/IIIa/Ib ITP plasma collected from an acute ITP patient at diagnosis. MNCs from the same umbilical cord blood was used for the cultures in panels B and C. None of the cells in this field stained positive for CD41. Original magnification, × 200.