Graffi Virus and Immunological Tolerance in Leukaemogenesis

Abstract

WE have tried to elucidate the possible influence of immunological mechanisms in virus leukaemogenesis of mice. We used Graffi virus, which has been proved to be most leukaemogenic in many strains of mice when injected at birth^1,2. In a preliminary investigation (C3Hf/Gs × CBA-T6T6)F_l mice (hereafter called CCH) were inoculated subcutaneously, when 1, 15 and 20 days old, with 0.05 ml. of 20 per cent w/v cell-free extract containing Graffi virus. The mice were observed for development of leukaemia. The extracts which were obtained from C57BL mice with generalized leukaemia induced by the same virus were prepared as described before¹. As shown in Table 1, a remarkable decrease in the incidence of leukaemia was observed in inverse relationship to the age at inoculation—from almost 100 per cent incidence in mice injected at birth to 12 per cent in animals injected when 15–20 days old. These results confirm that neonatal age is important in determining the neoplastic response of CCH mice to leukaemogenesis by Graffi virus.