Heart and spleen twin grafts in rats. II. Delayed host splenectomy

Simultaneous auxiliary transplantation of the spleen has been shown to delay and attenuate the rejection of cardiac grafts in rats. In the experiments reported here, 144 such twin grafts in Lewis and ACI rats were explored in an attempt to determine whether removal of the host's spleen would further facilitate graft survival in this model. Thus, 87 rats were submitted to host splenectomy at various time intervals after implantation of the twin grafts. After considerable technical problems were overcome, it was found that this additional maneuver induced permanent (greater than 5 months) survival in 64% of Lewis-to-ACI twin grafts. The important requirement for this success was timing; delaying host splenectomy for 3 to 5 days after implantation of the twin graft was mandatory.