Monocyte IL-2Rα expression is associated with thrombosis and the JAK2V617F mutation in myeloproliferative neoplasms

The development of bone marrow fibrosis and thrombosis are main causes of morbidity in essential thrombocythemia (ET). Monocyte activation has been associated to the production of fibrosis-related cytokines and pro-thrombotic factors. The aim of this study was to identify new markers of monocyte activation in Phi-negative myeloproliferative neoplasms and to search for their relationship with clinical features. Forty-five patients comprising 30 ET, eight myelofibrosis and seven polycythemia vera were included. We evaluated the α subunit of IL-2 receptor (CD25) on monocytes, basal and LPS-induced IL-1β release from mononuclear cells, and monocyte TGF-β mRNA content.Patients who had thrombotic events displayed higher monocyte CD25 levels (6.2%) than those without symptoms (1.3%) and controls (2.6%), p = 0.0006. JAK2V617F-positive patients had higher monocyte CD25 expression levels (4.7%), than JAK2V617F-negative (2.6%), p = 0.0213. Patients with myeloproliferative neoplasms had similar monocyte CD25 expression than controls, both, in basal conditions and after cell adhesion. IL-1β release and TGF-β mRNA levels were normal. In conclusion, increased monocyte CD25 expression is associated with history of thrombosis and is also up-regulated in patients harboring JAK2V617F mutation. The finding of increased CD25 levels together with normal IL-1β and TGF-β production reveals a selective monocyte activation profile in myeloproliferative neoplasms.