Allograft tolerance as in immunologically active process: analysis in a restricted H-2 incompatibility due to...

Cell-free spleen and liver extracts were used for attempted induction of allograft tolerance across a restricted H-2 barrier due to a chemically induced mutation in the B10.D2 mouse strain. When using mice of the latter strain as donors and the new congenic strain carrying the mutant H-2 hyaplotype as recipients, and with long-term administration of the cell-free antigens in adult life up to 100% yields (according to the dose of antigen) of permanently tolerant animals (particularly males) was obtained with spleen extract, but not with liver extract. This contrasts with a higher tolerance-inducing efficiency of liver extracts in various non-H-2 incompatibilities. In the reversed donor-recipient combination, neither spleen nor liver extracts gave positive results. The immune status of the permanently tolerant animals was analyzed and it was shown that with their bone marrow normal responsiveness can be conferred upon lethally irradiated syngeneic hosts whereas the specific allograft tolerance can be adoptively transferred to sublethally irradiated recipients by means of spleen or lymph node cells. It is concluded that in the present system the state of allograft tolerance is maintained by an immunologically active process of peripheral lymphocytes.