Differentiation of normal and PV erythroblasts in the presence of death receptor stimulation. (A) Percentages of basophilic erythroblasts in normal (N) and PV (PV) erythroid cell populations at day 14 of culture, untreated (NT), or treated with 50 ng/mL anti-CD95 antibody (CD95) from day 5 in standard erythroid medium containing 0.5 U/mL EPO. Data represent the mean ± SD of cell percentages obtained from May-Grünwald-Giemsa stainings prepared with erythroblasts from 13 patients and 9 healthy controls. The difference between normal and PV erythroblasts is not statistically significant. (B) May-Grünwald-Giemsa staining of erythroblasts derived from 1 healthy donor (N) and 1 PV patient (PV) at day 14 of differentiation in the presence of 50 ng/mL anti-CD95 antibody. Images were captured as described in the legend of Figure 1D. (C) Absolute number of mature (orthochromatic) erythroblasts obtained from healthy controls (N) and patients with PV (PV) characterized for the presence of the JAK2 V617F mutation at day 14 of culture in the presence of 50 ng/mL anti-CD95. Horizontal bars indicate the mean value of the N and PV erythroblasts.