Intravenousimmunoglobulin (IVIG) therapy caused similar effects thus suggesting that itstherapeutic effect could depend on modulation of IL1 isoforms and its receptor levels.Galle et al. [23] and Keskin et al. [17] revealed also that IVIG exertsanti-IL-6 properties thus to some extent, explaining mechanisms of its activityin PV patients. This evidence concerns the gene IL1B and acquired polycythemia vera.