Cellular aspects of tolerance. V. The in vivo cooperative role of accessory and thymus derived cells in responsiveness and unresponsiveness of SJL mice

Adult (8-week-old) SJL mice reach a relatively low degree of tolerance when injected with aggregate free rabbit γ-globulin (RGG). To analyze this phenomenon, we first examined indirect plaque-forming responses (PFC) in terms of participation of accessory and thymus-derived cells. Double transfer experiments were used; accessory cells were removed from donor cells by filtration over glasswool and their capacity reduced in recipients by 3 day preirradiation or by horse erythrocyte-mediated blockage. Using this type of experimental arrangement we found that the antibody response to RGG required the cooperation of accessory and thymus-derived cells. The induction of tolerance was affected by the presence of accessory cells. Preirradiated secondary recipients were reconstituted with spleen cells from accessory cell-deprived donors which had received thymus and bone marrow cells. In some experiments, the thymus and bone marrow cells were passed over glasswool. The primary recipients were left untreated or were given tolerogen. A more profound state of tolerance (reduction in plaque forming response) was the consequence of the incapacitation or removal of accessory cells. The magnitude of the reduction in PFC was directly related to the completeness of accessory cell removal and incapacitation. Responsiveness could be restored by administration of irradiated spleen cells as a source of accessory cells. The need for thymus-derived (T) cells in the antibody response was demonstrated by double transfer experiments in which the primary recipient was restored with thymus cells alone, bone marrow cells alone, or with a mixture of cell types.