IL17A and cancer: IL-17A–producing γδ T cells not only infiltrate human tumors (Boufea et al., 2020; Kargl et al., 2017; Wu et al., 2014), but high levels of IL-17A or abundance of γδ T cells also correlates with poor prognosis and metastasis in cancer patients (Benevides et al., 2015; Ma et al., 2012; Wu et al., 2014).