Electron microscopy evaluation of MP generated from purified CD34⁺ cells cultured for 7 days in the presence of MIP-1α, IL-3, IL-6, IL-11, FL, SCF, and MGDF. In (A) (original magnification × 11,230), an MP cell shows a sparse chromatin, a nucleolus, and few vacuoles and polyribosomes; the cell outline shows some microvilli and few gold particles indicating CD61 labeling (see arrow in the inset; original magnification × 25,120). A significantly more pronounced CD61 labeling is shown in the more differentiated MP in (B) (original magnification × 9,250).