GENETICS OF THE BLOOD TRANSFUSION EFFECT ON HEART ALLOGRAFTS IN RATS

Working with the recently available recombinant haplotypes of the rat major histocompatibility complex (MHC)—RT1, we investigated the effect of various types of blood transfusion (BT) on allograft prolongation, including blood identical for the whole RT1 haplotype with that of the donor or for only a part of it. One or two milliliters of donor blood significantly prolonged graft survival in the (LEWXBN)F1$$LEW or the LEW.1W$$LEW.1A combination. The optimal regimen consisted of two BTs given 15 and 7 days prior to grafting; BTs given at day-30 were ineffective. A BT given on the day of the operation was effective, but sequential BTs after grafting did not further increase graft survival. In the (LEWxBN)F1$$LEW combination, blood from congenic LEW.1N rats significantly prolonged graft survival, but third-party BTs were ineffective or had only a borderline effect when transfused (1 ml, 8 times) within the three months before transplantation. This showed the major role of the RT1 system as well as the specificity of the model. Although the survival of LEW.1A heart graft transplanted into LEW.1W recipients could not be significantly prolonged by donor blood, with the reverse—and “weaker”—combination (LEW.1W$$LEW.1A), 2 ml of donor blood led, in all cases, to > 100 days graft survival. In this last combination, third-party BT (LEW.1N) was again totally ineffective. Blood from RT1-recombinant rats was used to test the role of the respective RT1.A, B, and C regions, in the enhancing effect. BTs from LEW.1AR2 or LEW.1WR2 recombinants—sharing, respectively, RT1.C and RT1.A with the graft donor—were only moderately effective, as compared with BTs from the graft donor. On the other hand, LEW.1WR1 BTs—sharing the RT1.A and RT1.B regions with the graft donor—had a much more powerful effect on heart survival. The results strongly suggest that the RT1.B region (coding for Ia-like antigens) must be shared by the graft and blood donor in order to mediate a significant graft prolongation.