In light of our findings that demonstrate the role of IL-31 in antitumor immunity, we evaluated the potential of using IL-31 as a therapeutic intervention for cancer, similar to other immunomodulatory cytokines such as IL-2.37 A significant proportion of cytokines has a short half-life in the circulation.38 Previously, we designed a recombinant human IL-31 cytokine fused to an IgG backbone that was stable in the blood and demonstrated antitumor activity in vivo.11 However, a similarly designed murine IL-31-IgG was unable to induce IL-31Ra signaling in vitro. This evidence concerns the gene IL31 and cancer.