In particular, Th1 and Th17 appear to play a predominant role in PV pathogenesis, with PV patients exhibiting higher levels of inflammatory Th1 (IL-1RA, IL-1β, IL-2, IL-12p70, GM-CSF, TNF-α, IL-18) and Th17 cytokines (IL-17, IL-22, IL-23) than healthy controls [166,167]. This evidence concerns the gene IL22 and acquired polycythemia vera.