MHC-I expression acts as dominant tumour antigen in our model as evidenced by the following observations: (1) when MHC-I expression was up-regulated on B16 melanoma cells by pre-incubation with IFN-γ, the adaptive immune response was stronger and associated with alloreactive antibody production and the inhibition of tumour progression (Figure 2); (2) injection of EL-4 lymphoma (H-2Kb) and MC38 colon cancer cells (H-2Kb) which express normal levels of MHC-I antigens provoked strong alloreactive immune response and were rejected by the allogenic hosts (Figure 2). This evidence concerns the gene IFNG and lymphoma.