IFNG and cancer: Since, both these cell lines were engineered to express MHC-II constitutively and expression of MHC-II in non-APCs, including most cancer cells, is not constitutive but driven by the IFNγ-induced CIITA promoter pIV (34) we engineered B16 cells to express transgenic MHC-II under an IFNγ-inducible promoter (iDR4.