CD274 and myeloproliferative neoplasm: First, the primary overactivation of JAK/STAT pathways in JAK2V617F + clonal cells (including monocytes, megakaryocytes and platelets) directly induced the overexpression of programmed cell death (PD-1) ligand 1 (PD-L1), thus supporting the idea that MPN cells exploit the PD1/PD-L1 axis to escape specific T cell immunosurveillance [113].