| Abstract: | Parental thymocytes, inoculated into F1 mice which have been depleted of lymphoid cells by lethal irradiation, react to the host antigens which are contributed by the reciprocal parent in the F1 cross, by synthesizing DNA. The amount of DNA the parental thymocytes synthesize can be regulated by the addition of F1 thymocytes to the lethally irradiated F1 recipient. F1 thymocytes suppress the response of a highly responding inoculum of parental thymocytes and boost the response of an inoculum responding less well. These regulatory effects of F1 thymocytes are not abolished by 900 R of irradiation. 900 R-irradiated parental cells which are themselves incapable of DNA synthesis can also affect the response of DNA synthesizing cells. As with F1 thymocytes, the effect that 900 R-irradiated parental thymocytes has depends on the activity of the DNA synthesizing population; when it is high the effect is suppressive, when it is low there is augmentation. These results indicate that during the course of their response to antigen, T cells may transmit signals to other T cells which in turn transmit feedback signals to the primarily responding cells and in so doing alter their response. Such circular interactions between T cells may play an important role in immunological homeostasis. |
