IL33 and leukemia: To test if IL-33 treatment protects cells from apoptosis, we stained leukemia cells with Annexin V. We found that IL-33-treated cells had statistically significant lower Annexin V staining, and increased viability, as compared to the untreated cells, and the anti-apoptotic effect of IL-33 was blocked by the addition of anti-IL1RL1 antibody (Fig. 6G,H).