IL17A and acquired polycythemia vera: Research has highlighted the vital roles of adaptive immune molecules, such as IL-17, IL-23, and TNF-α (1), in PV, which has allowed the development of multiple effective therapies targeting tumour necrosis factor-alpha (TNF-α; adalimumab), IL-17A (secukinumab), IL-17 receptor A (IL-17RA; brodalumab), and IL-23 (guselkumab) (2–4).