BM and spleen analysis. BM cellularity (A), spleen weight (B) and differential cell count (BM cells [C] and spleen cells [D]) of these organs in recipient mice. BL indicates blast; MY, metamyeloblast/myeloblasts; ME/PO, myelocyte/neutrophil; LY, lymphocyte; MO, monocytes; EO, eosinophil; and ERY, erythroblasts. White, gray, and black histograms are empty, JAK2^WT, and JAK2^V617F virus-recipient mice (n = 8-12), respectively. For BM cellularity and spleen weight, data from the JAK2^V617F virus-recipient mice were pooled (JAK2^V617F) or divided into mice studied less (n = 7, days 52-97) or more (n = 5, days 131-143) than 4 months after transplantation (less than or more than 4 months). Differential counts were carried out of cells collected between days 31 and 143 after transplantation (n = 8), with a tendency toward an increase in the percentage of erythroblasts in late transplantation stages. ^*P < .05 compared with the JAK2^WT mice.