Tolerance and leukaemogenesis.

Two subjects are considered here separately. Both are related to findings in the early embryo aggregation derived mouse chimaera model. Such chimaeras are most commonly derived following the aggregation of two undifferentiated embryos and therefore not suprisingly they were originally considered examples of "classic" immunological tolerance. Since this time alternative mechanisms including humoral and cell suppressor activity have been suggested and until recently tolerance in tetraparental chimaeras has remained a controversy. This controversy is now reviewed in the light of recent findings which has suggested that such mice are in fact examples of classic tolerance with the possibility that this is achieved by heterogeneous elimination of the clone of potentially self in equilibrium self auto-reactive cells. Chimaeras have also been studied in respect of leukaemogenesis. Results in a group of AKR reversible CBA leukaemia susceptible reversible resistant chimaeras suggest resistance is dominant. Moreover evidence now points to lack of anti-viral antibody activity in these chimaeras which I wish to suggest may be related to apparent resistance to leukaemia. In this context it may be envisaged that in the absence of masking anti-viral antigen complexes "normal" tumour immunity may have been effected. Although this has yet to be proven evidence points to tolerance to the oncogenic virus being maintained in the chimaeras furthermore also in the naturally derived (AKR X CBA) F1. This in turn leads me to suggest that "intolerance" to the oncogenic virus, the spontaneous development of anti-viral antibodies and tumour development might well be related in the AKR. This in turn enables me to propose that tolerance and leukaemogenesis, at least in this stiuation, appear to be related.