Difference in the target cells for tolerance induction in relation to the dose of tolerogen.

Bone marrow cells and thymus cells were observed in cell transfer experiments to collaborate in the production of anti-BSA antibodies. The target cells for tolerance induction either with a low dose' of antigen (100 μg of deaggregated BSA once a week × 5) or with a high dose' (a single injection of 5000 μg) were identified by the same technique. In low dose' tolerance, some indication was obtained that thymus-derived cells in peripheral lymphoid systems were the target cells; bone marrow-derived cells appeared not to be so susceptible, and the cells residing in thymus or bone marrow seemed to remain unimpaired. In contrast, the injection of a high dose' of tolerogen rendered both types of cells in spleen, thymus cells and bone marrow cells, unresponsive or hyporesponsive in parallel with one another.