TNF and acquired polycythemia vera: The basic pathogenesis of PV involves aberrant cross-talk between the innate and adaptive immune systems, with central roles for the interleukin-23/interleukin-17 (IL-23/IL-17) axis, tumor necrosis factor-alpha (TNF-α), and particular skin cells such as dendritic cells and keratinocytes (Boehncke and Schön, 2015).