In agreement with these findings, our data suggest that the spontaneous downregulation of MHC class I on tumour cells contributes to tumour evasion from immunosurveillance; to our knowledge, these advanced tumours have not previously been curable by a single immunotherapy relying on endogenous immune responses, but IL-21 secretion by NKT-cell-activating vaccination or IL-21-mediated NK-cell therapies effectively eradicate these tumours by reversing NK-cell exhaustion. Here, IL21 is linked to neoplasm.