IL9 and neoplasm: The previous reports showing anti-tumoural properties of Th9 and Tc9 cells29–31 allied to our results demonstrating no difference in the frequency of IL-9-producing non-T cells in the lungs of ABX-treated mice raised the question whether IL-9 treatment would be sufficient to improve tumour control in those animals as compensation for the lower number of Th9 and Tc9 cells.