For instance, the absence of IFN-γ led to an augmented tumour growth in the AOM/DSS model, thereby affecting anti-tumour immune responses.43 Conversely, Th1 signatures were associated with an improved prognosis in CRC patients.44 However, Th17 clusters predicted a poor prognosis.44 IL-23 and IL-17 favoured barrier defects and tumour growth in experimental colorectal cancer models.45 In contrast to these findings on Th1 and Th17 cytokines, little is known about the role of Th9 cells in CRC. This evidence concerns the gene IL17A and infectious otitis media.