The B16-F1 melanoma and E.G7 OVA-expressing thymoma47 (link) were obtained from the American Type Culture Collection, Manassas, VA. The B16.OVA melanoma48 (link) was kindly provided by Dr Roslyn Kemp, Trudeau Institute. EL-4 thymoma cells were a gift from Prof. Michael Berridge, Malaghan Institute of Medical Research. All cell lines were maintained in complete Iscove's modified Dulbecco medium as described.19,49 (link) Extended in vitro passaging was avoided. Mice were injected with either 105 (B16-F1, B16.OVA) or 5 × 105 (E.G7-OVA, EL-4) cells s.c. into the flank. Tumor size and survival were calculated as described.19 (link)