Homologous disease reactivation by x-radiation.

Hybrid F(1) mice (BDF(1)) that failed to develop homologous disease after injection of parental (C57 Bl/6) spleen cells were treated with 400 roentgens of total body x-radiation 13 months later. Typical homologous disease promptly developed in these mice. This suggests that parental lymphoid cells may acquire immunologic tolerance to "foreign" host antigens and that the tolerant state is disrupted by sublethal doses of radiation.