Ultrastructure of megakaryocytes cultured with or without IFN-α2b. (A) Ultrastructures of representative human megakaryocytes cultured with 10 ng/mL TPO, 10 ng/mL TPO plus 10 ng/mL IFN-α2b, and 10 ng/mL TPO plus 10 ng/mL IFN-α2b plus 1 μg/mL NIP-004. ◁ represent type 1 immature megakaryocytes (i-iii); ◀, type 2 intermediate megakaryocytes (iv-vi); , type 3 fully matured megakaryocytes (vii-ix). The definition of each type is in “Electron microscopy.” Original magnification, ×3000. Scale bar represents 4 μm. N indicates nucleus; Dm, demarcation membranes. (B) The percentage of each type of megakaryocytes. IFN-α2b decreased type 3 megakaryocytes and increased type 2 compared with control (TPO) with statistically significant differences, indicating that IFN-α2b inhibits the development of the demarcation membrane system of megakaryocytes. Data are means plus or minus SD from the results of 4 independent experiments (*P < .05 vs TPO). NIP-004 prevented the inhibitory effects of IFN-α2b on the development of the demarcation membrane system of megakaryocytes. Data are means plus or minus SD from the results of 2 independent experiments (#P < .05 vs TPO + IFN).