Kinetic studies of immune tolerance induction to HSA in sublethally X-rayed rabbits revealed that tolerance can be induced in this system with small amounts of antigen which in non-irradiated animals would constitute small immunizing doses. This, however, depends on a proper schedule of antigen administration which has to be spread over the 8 weeks of post-radiation recovery, although tolerance can be induced by this method even when this antigen treatment is postponed as long as 4 weeks after X-irradiation.
Since the lymphoid system recovers rapidly from sublethal radiation injury, and since it was found that by the end of 4 weeks the lymphoid organs demonstrate good cellular repopulation, the conclusion was arrived at that the two processes, namely that of lymphoid recuperation and that of transition from susceptibility to tolerance into the state of immunocompetence, progress independently. These observations raise some questions relevant to theories of the cellular basis of immune tolerance.