DENV infects human MKs and upregulates IFITM3. (A) CD34⁺-derived MKs (culture day 12) were incubated (t = 18 hours) with mock virus (mock) or DENV2 (MOI 1.0). After incubation, MKs were stained by immunocytochemistry against DENV2 antigen (green). Nuclei are stained with 4′,6-diamidino-2-phenylindole (DAPI) (blue). Data shown in this figure are from 5 to 6 independent experiments per group. (B) Heat map showing differential levels of expression in CD34⁺-derived MKs (culture day 12) incubated (t = 18 hours) with mock or DENV2 (MOI 1.0). (C) Scatter plot showing significantly (adjusted P < .05) enriched (red) and repressed (blue) transcripts in dengue-infected MKs compared with mock-infected MKs. IFITM3 is indicated. (D-E) CD34⁺-derived MKs (culture day 12) were incubated (t = 18 hours) with mock or DENV2 (MOI 1.0). IFITM3 was measured by using quantitative RT-PCR (D) and immunoblot densitometry (E). Dengue-infected CD34⁺-derived MKs (and mock-infected control MKs) were stained with antibodies against CD41 (a mature MK marker) and IFITM3. Intracellular IFITM3 expression in CD41⁺ mature, human MKs was quantified by using flow cytometry. (F) Representative histograms. Quantification is shown in percent positive cells (G) and mean fluorescence intensity (MFI; H), n = 6.