Figure 1. Generation of immortalized adult erythroid cell line.

Human adult bone marrow CD34⁺ cells were recovered from frozen primary erythroid culture medium for 24 h, before transduction with Tet-inducible HPV16 E6/E7 construct. Cells were transferred to StemSpan expansion medium with doxycycline on day 5 in culture and maintained in expansion medium thereafter. (a) Schematic of experimental approach. (b) Representative cytospins illustrating similar morphology of cells maintained proliferating in continuous culture on days 57, 125 and 164. (c) Representative cytospin images showing morphology of cells on days 4, 10 and 18 following transfer to erythroid differentiation medium and of reticulocytes isolated by filtration. Cytospins of erythroid cells differentiated from adult peripheral blood CD34⁺ at comparative stages of differentiation are included for comparison. Cells were stained with May–Grunwald Giemsa reagent and analysed by light microscopy. Scale bars 10 μm.