IL33 and neoplasm: Eosinophil depletion using anti-Siglec-F antibodies was used in the past to evaluate the engagement of eosinophils in tumor reduction.12,25 A recently published article now suggests that eosinophil depletion by anti-Siglec-F antibodies does not result in reduction of eosinophil numbers but rather in an inhibited interaction of Siglec-F with its ligands leading to the observed biological effects.55 Therefore, we used ∆dblGATA-1 mice in order to test whether the anti-tumorigenic effect of IL-33 treatment was dependent on the presence of eosinophils.