[Inhibition of acute rejection of heart graft in rats without immunosuppressants after intrathymic myocardial cell inoculation in the neonatal period].

There have been no successful cases reported of organ transplantation in application of neonatal immunological tolerance. Isolated myocardial cells from Lewis (LEW/Crj) rat hearts were inoculated into the thymus of incompatible King (WKAH/Hkm) rats. Ten weeks later the heart from LEW donor was transplanted heterotopically to the WKAH rat that had inoculated intrathymic myocardial cells without immunosuppression (n = 4, Group 1). Group 2 was made up of 4 isografts of heart transplantation (nontreated isograft). Group 3 was made up 4 allografts of heart transplantation (nontreated allograft). The animals were killed 7 days after transplantation, and early rejection was evaluated by accumulation of iodine-125 (125I)-labeled antimyosin antibody (AMA) uptake and confirmed by histological examination. In Group 1 & 2, the value of I-125 AMA uptake ratio was small (Group 1; RV: 1.28 +/- 0.28, IVS: 1.29 +/- 0.28, LV: 1.43 +/- 0.25, Group 2: RV: 1.14 +/- 0.07, IVS: 0.95 +/- 0.06, LV: 1.16 +/- 0.21). This level of the value indicates that the rejection does not occur. On the other hand, in Group 3, the value was high (RV: 4.63 +/- 1.92, IVS: 4.42 +/- 1.75, LV: 4.45 +/- 1.73) compared with Group 1 & 2. This level indicate that the rejection is severe. In the histological studies, Group 3 showed necrosis of myocardial cells, while Group 1 with neonatal immunological tolerance showed only very mild lymphocytic infiltration. The histology of thymic tissue in Group 1, the LEW myocardial cells are surviving in the WKAH rat thymus.