The use of early embryo aggregation derived chimaeras. I. To study immunological tolerance

Early embryo aggregation mouse chimaeras have proven an invaluable tool to study mechanisms involved in tolerance. 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 heterogenous elimination of the clones of potentially self in equilibrium self auto-reactive cells.