IL4 and acquired polycythemia vera: Currently, B-cell inhibitors including rituximab and TNF-α inhibitors including etanercept, infliximab, sulfasalazine, and pentoxifylline have demonstrated efficacy in treating PV.21, -23 Given the mechanistic role of IL-4 in PV pathogenesis and the correlation of IL-6 levels with PV disease severity, it would be interesting to determine if IL-4 or IL-6 inhibitors provide therapeutic benefit in PV.