Flow cytometric analysis of animals that underwent transplantation with JAK2WT and JAK2T875N. Following red blood cell lysis, total spleen cells from JAK2WT or JAK2T875N animals were analyzed by flow cytometry for expression of several lineage cell surface markers. Compared with cells from animals that underwent transplantation with JAK2WT, spleen cells from JAK2T875N mice exhibited significantly increased percentages of mature myeloid (A), erythroid (B), and megakaryocytic (C) elements. No increase in the percentage of CD42b-expressing cells was detected between JAK2WT and JAK2T875N animals (D). The increase in the number of CD41-expressing cells (megakaryocytes) in JAK2T875N mice was even more prominent when the analysis was performed on GFP-positive gated spleen cells (E).