IL21 and acquired polycythemia vera: In aggregate, cytokines including Th2 (IL-4, IL-5, IL-10), Th17 (IL-17, IL-21, IL-23, TGF-β), and other pro-inflammatory cytokines (IL-6, IL-8, TNF-α, IL-1) exhibit heightened expression in PV, with certain cytokines correlating positively with disease severity and autoantibody titers, and their diminished expression post-successful treatment.