IL2 and acquired polycythemia vera: Higher levels of soluble IL‐2Rα (sIL‐2Rα) have also been observed in patients with myelofibrosis relative to either patients with polycythaemia vera (PV)/ET or healthy controls8 and increased IL‐6, IL‐2 and sIL‐2Rα have been demonstrated in patients following progression from ET and PV to myelofibrosis.23