DNAM-1+ (but not DNAM-1−) NK cells from normal B6 mice could sense the absence of MHC-I on tumour target cells and perform missing self-killing in vitro. All these observations suggest a strong association between DNAM-1 expression and education state, even when the latter is altered in mature NK cells in a manner consistent with the ‘rheostat model'. This evidence concerns the gene CD226 and neoplasm.