ROLE OF IA-POSITIVE CELLS IN THE BENEFICIAL EFFECT OF DONOR BLOOD TRANSFUSION AND INDUCTION OF SUPPRESSOR CELLS IN CARDIAC ALLOTRANSPLANTATION OF RATS

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Abstract
An attempt was made to reveal the role of Ia-positive cells in the beneficial effect of pretransplant donor-specific blood transfusion (DST) and induction of suppressor cells in the cardiac allotransplantation of rats. Mean graft survival time (MST) of F344 (RTl1v1) hearts transplanted in WKA (RTlk) rats was 6.5±0.8 days. Pretreatment of recipients with 1 ml DST 10 days before grafting prolonged it to 56.5±38.1 days. Plasma or erythrocytes did not prolong MST at all, whereas pretreatment with 1×107 lymphocytes prolonged MST significantly. B enriched cells separated on a nylon-wool column prolonged MST, but T-enriched cells did not. Treatment of lymphocytes with interspecies crossreactive monoclonal anti-Ia antibody and complement eliminated the ability of lymphocytes to prolong MST, suggesting an important role of Ia-positive cells in the beneficial effect of DST. The role of Ia-positive cells in prolonging graft survival, was analyzed by a cell and serum transfer experiment. MST of F344 heart allografts transplanted in sublethally irradiated (500 rads) WKA rats was 17.4±4.0 days. MSTs of allografts in rats irradiated and treated with serum or spleen cells of blood-conditioned rats were 23.2+1.6 (P < 0.05) and 5.2±0.7 (NS) days, respectively. On the other hand, MSTs of the grafts in rats irradiated and treated with serum or spleen cells harvested from rats that had accepted grafts for 30 days were 18.7±1.9 (NS) and 63.8±29.9 (P < 0.01) days, respectively. The results indicate that the initial role of a serum factor in prolonging graft survival induced by DST containing Ia-positive cells was followed by activating suppressor cells by the presence of the allograft.