As displayed in Figure 4A and 4B, serum levels of IL-4 and IL-13 were also increased in patients with PV, compared with healthy control subjects (28.65 ± 0.803 pg/ml vs. 24.15 ± 1.059 pg/ml, p = 0.001; 43.67 ± 3.624 pg/ml vs. 31.44 ± 2.746 pg/ml, p = 0.013; respectively). Here, IL13 is linked to acquired polycythemia vera.