We could demonstrate that the PD‐L1 expression in CD34+CD45dimCD38− stem cells of JAK2‐V617F positive MPN patients spontaneously decreases when the cells are incubated ex vivo in RPMI medium for 24 h, and that the stimulation with IFN‐γ restores PD‐L1 expression to normal baseline levels. The gene discussed is JAK2; the disease is myeloproliferative neoplasm.