Abstract
Summary
By inoculation of 40 × 106 (A × T6)F1 spleen cells intraperitoneaUy into newborn A strain mice incomplete tolerance of varying duration was established to skin grafts of the spleen donor strain. Three long-term incompletely tolerant A mice were cellular lymphoid chimeras with 2.3% of T6 positive donor cells in their spleens when sacrificed at 116 days after skin grafting. Lymphoid cells (30 × 1016) from 3 comparable animals sacrificed at 130 days produced fatal homologous disease when injected into sublethally irradiated (A × T6)F1 hybrids. The F1 hybrids succumbed after a longer latent period (19-78 days) than after injection of lymphoid cells (30 × 106) from control strain A mice (10-26 days).
Seven strain A mice with short-term tolerance (15 to 55 days), did not immediately regain their immunological reactivity. A second test graft of the same origin placed after rejection of the first graft survived for periods remarkably similar to those for the first graft. When 2 comparable short-term tolerant mice were tested for chimerism, each of them contained a small percentage of donor dividing cells in the spleen at 33 days after skin graft rejection (7/103 and 1/64 respectively).
Four nontolerant mice (graft rejected within 14 days) did not display any detectable lymphoid chimerism (0/40 for each) when tested shortly after the rejection of the test graft.
In 2 strain A mice with complete tolerance to (A × T6)F1 skin homografts for 26 months as a result of intravenous and intraperitoneal injection of F1 spleen cells at birth, the graft remained fully preserved in spite of very low levels of lymphoid chimerism at the time of sacrifice.
We are grateful indeed to the Department of Physics, M.D. Anderson Hospital and Tumor Institute for providing us with the irradiation source.
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