This effect was seen both in basophils analysed ex vivo from bone marrow cells of MPLW515L mice (Fig. 5E) as well as basophils differentiated ex vivo from MPLW515L vs. control HSPCs (Fig. S5C), indicating that the induction of TNF and IL4 occurred as a direct effect of the MPN driver mutation and was not dependent on niche reprogramming. Here, TNF is linked to myeloproliferative disorder.