| Abstract: | Spleen allografts from (2 X 13)F1 donors survive indefinitely in immunologically intact strain 2 recipients. Such strain 2 hosts with long-term surviving F1 grafts had markedly suppressed anti-13 MLR responses and cells capable of suppressing the response of normal strain 2 cells to strain 13 stimulators were present in some long-term surviving animals. In order to further analyze the cellular basis for this tolerant state, we transferred cells from tolerant donors to normal syngeneic strain 2 hosts. We showed that such suppressor cells transfer MLR unresponsiveness to primary or secondary hosts, but that the period of MLR suppression is rather short-lived. Strain 13 cardiac allografts survived indefinitely in cell-transferred primary or secondary hosts and further enhanced MLR suppression, whereas most cardiac allografted controls had vigorous MLR responses for strain 13 stimulator cells after rejection of their transplants. Attempts to abrogate established tolerance in transferred hosts, either by donor antigen or by host cytolytic T cells were unsuccessful. |
